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Freescale Semiconductor Technical Data
MPR084 Rev 2, 04/2008
Product Preview Proximity Capacitive Touch Sensor Controller
MPR084 OVERVIEW The MPR084 is an Inter-Integrated Circuit Communication (I2C) driven Capacitive Touch Sensor Controller, optimized to manage an 8-touch pad capacitive array. The device can accommodate a wide range of implementations through 3 output mechanisms, and many configurable options. Features * * * * * * * * * * * * * * * * * * * * * * * * 1.8 V to 3.6 V operation 41 A average supply current with 1 s response time 2 A low Standby Current Variable low power mode response time (32 ms - 4 s) Rejects unwanted multi-key detections from EMI events such as PA bursts or user handling Ongoing pad analysis and detection is not reset by EMI events Data is buffered in a FIFO for shortest access time IRQ output advises when FIFO has data System can set interrupt behavior as immediate after event, or program a minimum time between successive interrupts Current touched pad position is always available on demand for polling-based systems Sounder output can be enabled to generate key-click sound when pad is touched Two hardware selectable I2C addresses allowing two devices on a single I2C bus Configurable real-time auto calibration 5 mm x 5 mm x 1 mm 16 lead QFN package -40C to +85C operating temperature range Control Panels Switch Replacements Touch Pads Appliances PC Peripherals Access Controls MP3 Players Remote Controls Mobile Phones ORDERING INFORMATION
Device Name MPR084Q MPR084EJ -40C to +85C Temperature Range Case Number 1679 (16-Lead QFN) 948F (16-Lead TSSOP) Touch Pads
MPR084
Capacitive Touch Sensor Controller
Bottom View
16-LEAD QFN CASE 1679
16-LEAD TSSOP CASE 948F
Top View
E1 E2 E3 14 E4 13 12 E5 11 E6 10 E7 9 5 SCL 6 SDA 7 AD0 8 SOUNDER E8
16 ATTN IRQ VDD VSS 1 2 3 4
15
MPR084
Implementations
Typical Applications
ATTN IRQ VDD VSS SCL SDA AD0 SOUNDER
1 2 3 4 5 6 7 8
16 15 14
E1 E2 E3 E4 E5 E6 E7 E8
MPR084
13 12 11 10 9
8-pads
Figure 1. Pin Connections
This document contains a product under development. Freescale Semiconductor reserves the right to change or discontinue this product without notice.
(c) Freescale Semiconductor, Inc., 2007, 2008. All rights reserved. Preliminary
1
1.1
Device Overview
Introduction
Freescale Semiconductor's MPR084 proximity capacitive touch sensor controller is one of a family of products designed to detect the state of capacitive touch pads. The MPR084 offers designers a cost-efficient alternative to mechanical keys for control panel applications. The MPR084 uses an I2C interface to communicate with the host which configures the operation and an interrupt to advise the host of status changes. The MPR084 includes a piezo sounder drive which provides audible feedback to simulate mechanical key clicks. The MPR08X family has several implementations to use in your design including control panels and switch replacements. The MPR084 controls individual touch pads. Other members of the MPR08X family are well suited for other application interface situations such as individual touch pads or rotary/touch pad combinations. Freescale offers a broad portfolio of proximity sensors for products ranging from appliance control panels to portable electronics. Target markets include consumer, appliance, industrial, medical and computer peripherals.
1.1.1
Devices in the MPR08X series
The MPR08X series of Proximity Capacitive Touch Sensor Controllers allows for a wide range of applications and implementations. Each of the products in Table 1 perform a different application specific task and are optimized for this specific functionality. Table 1. MPR08X family Overview Product MPR083 MPR084 Bus I2C I2C Sounder Yes Yes Rotary/Slider 8-pads -- Touch Pad Array -- 8 keys
1.1.2
Internal Block Diagram
The MPR084 consists of primary functional blocks; Interrupt Controller, I2C Serial Interface, Sounder Controller, Configuration and Status registers, Touch Pad Decoder, Magnitude Comparator and Recalibrator, EMI Burst/Noise Rejection Filter, Capacitance Measurement Analog Front End. Each of these blocks will be described in detail in their respective sections.
CLEAR SDA SCL ATTN AD0 I2C SERIAL INTERFACE
PAD ENABLED CURRENT PAD
TOUCHED PAD IDENTIFY DECODER
EMI BURST/NOISE REJECT FILTER
RATE
CAPACITANCE MEASUREMENT A.F.E.
SET
CONFIGURATION AND STATUS REGISTERS
IRQ
INTERRUPT CONTROLLER
MAGNITUDE COMPARATOR AND RECALIBRATOR
MASKS
8
8
8
8
8 TOUCH PADS
SOUNDER
SOUNDER DRIVER CONTROLLER
Figure 2. Functional Block Diagram
MPR084 Preliminary 2 Sensors Freescale Semiconductor
1.1.3
Terminology
The following terms are used to describe front panel interface and capacitive touch sensor technology throughout this document. Table 2. Terminology Term Touch Sensor Touch Sensor Controller Key Touch Pad Definition A Touch Sensor is the combination of a Touch Sensor Controller and a connected conductive area referred to as an electrode. A Touch Sensor Controller is the intelligent part of a Touch Sensor which measures capacitance and differentiates between touched and untouched pads. A Key or Switch is a mechanical device that makes an electrical connection only when pressed. A Touch Pad is a type of capacitive sensor that is used for direct replacement of a Key. A capacitive touch sensor determines touch state by differentiating between high and low capacitances. When there is a change in the state this can be interpreted in the same way as a mechanical Key. A Solid or Full Pad is a type of touch pad where exactly one electrode is used A Split Pad is a type of touch pad where more than one electrode is used. Split Pads are used to increase the total number of possible touch pads without increasing the electrical connections to the Touch Sensor Controller. N-Key Lockout refers to the logic that determines how many keys can be simultaneously touched in a system. For example, 1-key lockout would only allow a single key to be touched before ignoring all future touches. N-Key Rollover refers to the logic that determines how many keys can be pressed in succession without releasing previous keys. For example, a system with 1-key lockout and 2-key rollover would allow 2-keys to be pressed in succession but would only report the second key once the first key was released. Inter-Integrated Circuit Communication
Solid Pad Split Pad
N-key Lockout
N-key rollover
I2C
MPR084 Sensors Freescale Semiconductor Preliminary 3
2
2.1
External Signal Description
Device Pin Assignment
Table 3 shows the pin assignment for the MPR084. For a more detailed description of the functionality of each pin, refer to the appropriate chapter. Table 3. Device Pin Assignment Pin 1 2 3 4 5 6 7 8 9 - 16 PAD Name ATTN IRQ VDD VSS SCL SDA AD0 SOUNDER E1, E2, E3, E4, E5, E6, E7, E8 Exposed pad Function Attention Pin. Input, active low, when asserted sets the Configuration Register's DCE bit high allowing communication with the part. Interrupt Request Pin. Output, active-low, open-drain interrupt request signaling new events. Positive Supply Voltage Ground I2C Serial Clock I2C Serial Data Address input. Low = slave address 0x5C. High = slave address 0x5D. Sounder driver output. Connect a piezo sounder from this output to ground. Output is push-pull Touch Pad Electrode connections. Exposed pad on package underside (QFN only). Connect to VSS.
The two packages available for the MPR084 are a 5x5mm 16 pin QFN and a 4x5mm 16 pin TSSOP. Both of the packages and their respective pinouts are shown in Figure 3.
E1
E2
E3
E4
16 ATTN IRQ VDD VSS 1 2 3 4 5 SCL
15
14
13 12 E5 11 E6 10 E7 9 E8
ATTN IRQ VDD VSS SCL SDA AD0 SOUNDER
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9
E1 E2 E3 E4 E5 E6 E7 E8
6 SDA
7 AD0
8 SOUNDER
QFN
Figure 3. Package Pinouts
TSSOP
2.2
Recommended System Connections
The MPR084 Capacitive Touch Sensor Controller requires ten external passive components. When connecting the MPR084 in a touch sensor system, the electrode lines must have pull-up resistors. The recommended value for these pull-ups is 780k. Some electrode arrays will require higher or lower values depending on the application. In addition to the 8 resistors a bypass capacitor of 10F should always be used between the VDD and VSS lines.and a 4.7 k pull-up resistor should be included on the IRQ. MPR084 Preliminary 4 Sensors Freescale Semiconductor
The remaining 5 connections are SCL, SDA, IRQ, ATTN, and SOUNDER. Depending on the specific application, each of these control lines can be used by connecting them to a host system. In the most minimal system, the SCL and SDA must be connected to a master I2C interface to communicate with the MPR084. All of the connections for the MPR084 are shown by the schematic in Figure 4.
VDD VDD
780k 780k 4.7k 780k 780k 780k
780k 780k 780k ARRAY
ELECTRODE 1 2 3 4 5 6 7 8 9
E1 E2 E3 E4 E5 E6 E7 E8 GND
VDD
ATTN IRQ
1 ATTN 2
IRQ
E1
16
1F
3 VDD 4
VSS SCL SDA
15 E2 14
E3 E4 E5 E6 E7 E8
13 12 11 10 9
5 SCL 6 7
AD0
SDA
GND
SOUNDER 8
SOUNDER
MPR084
GND
8-TOUCH PAD
Figure 4. Recommended System Connections Schematic Note that in this configuration the AD0 address line is tied high thus the slave address of the MPR084 0x5D. Alternatively the address line can be pulled low if the host system needs the MPR084 to be on address 0x5C. This functionality can also be used to incorporate two MPR084 devices in the same system.
2.3
Serial Interface
The MPR084 uses an I2C Serial Interface. The I2C protocol implementation and the specifics of communicating with the Touch Sensor Controller are detailed in the following sections.
2.3.1
Serial-Addressing
The MPR084 operates as a slave that sends and receives data through an I2C 2-wire interface. The interface uses a serial data line (SDA) and a serial clock line (SCL) to achieve bi-directional communication between master(s) and slave(s). A master (typically a microcontroller) initiates all data transfers to and from the MPR084, and generates the SCL clock that synchronizes the data transfer. The MPR084 SDA line operates as both an input and an open-drain output. A pull-up resistor, typically 4.7k, is required on SDA. The MPR084 SCL line operates only as an input. A pull-up resistor, typically 4.7k, is required on SCL if there are multiple masters on the 2-wire interface, or if the master in a single-master system has an open-drain SCL output. Each transmission consists of a START condition (Figure 5) sent by a master, followed by the MPR084's 7-bit slave address plus R/W bit, a register address byte, one or more data bytes, and finally a STOP condition.
SDA
tSU DAT tLOW tHIGH tR tF REPEAT ED ST ART CONDIT ION tHD DAT tSU STA tHD STA tSU STO
tBUF
SCL
tHD STA ST ART CONDIT ION
ST OP CONDIT ION
ST ART CONDIT ION
Figure 5. Wire Serial Interface Timing Details MPR084 Sensors Freescale Semiconductor Preliminary 5
2.3.2
Start and Stop Conditions
Both SCL and SDA remain high when the interface is not busy. A master signals the beginning of a transmission with a START (S) condition by transitioning SDA from high to low while SCL is high. When the master has finished communicating with the slave, it issues a STOP (P) condition by transitioning SDA from low to high while SCL is high. The bus is then free for another transmission.
SDA SCL
DATA LINE STABLE DATA VALID
CHANGE OF DATA ALLOWED
Figure 6. Start and Stop Conditions
2.3.3
Bit Transfer
One data bit is transferred during each clock pulse (Figure 7). The data on SDA must remain stable while SCL is high.
SDA SCL
S
START CONDITION
Figure 7. Bit Transfer
P
STOP CONDITION
2.3.4
Acknowledge
The acknowledge bit is a clocked 9th bit (Figure 8) which the recipient uses to handshake receipt of each byte of data. Thus each byte transferred effectively requires 9 bits. The master generates the 9th clock pulse, and the recipient pulls down SDA during the acknowledge clock pulse, such that the SDA line is stable low during the high period of the clock pulse. When the master is transmitting to the MPR084, the MPR084 generates the acknowledge bit because the MPR084 is the recipient. When the MPR084 is transmitting to the master, the master generates the acknowledge bit because the master is the recipient.
START CONDITION
SCL SDA SDA
CLOCK PULSE FOR ACKNOWLEDGEMENT 1 2 8 9
BY TRANSMITTER
S
Figure 8. Acknowledge
BY RECEIVER
MPR084 Preliminary 6 Sensors Freescale Semiconductor
2.3.5
The Slave Address
The MPR084 has a 7-bit long slave address (Figure 9). The bit following the 7-bit slave address (bit eight) is the R/W bit, which is low for a write command and high for a read command.
SDA SCL
1 MSB
0
0
1
1
0
0
R/W
ACK
Figure 9. Slave Address The MPR084 monitors the bus continuously, waiting for a START condition followed by its slave address. When a MPR084 recognizes its slave address, it acknowledges and is then ready for continued communication.
2.3.6
Message Format for Writing the MPR084
A write to the MPR084 comprises the transmission of the MPR084's keyscan slave address with the R/W bit set to 0, followed by at least one byte of information. The first byte of information is the command byte. The command byte determines which register of the MPR084 is to be written by the next byte, if received. If a STOP condition is detected after the command byte is received, then the MPR084 takes no further action (Figure 10) beyond storing the command byte. Any bytes received after the command byte are data bytes.
Command byte is stored on receipt ofSTOP condition acknowledge from MPR084
D7
D6
D5
D4
D3
D2
D1
D0
S
SLAVE ADDRESS R/W
0
A
COMMAND BYTE acknowledge from MPR084
A
P
Figure 10. Command Byte Received Any bytes received after the command byte are data bytes. The first data byte goes into the internal register of the MPR084 selected by the command byte (Figure 11).
acknowledge from MPR084 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 acknowledge from MPR084 D3 D2 D1 D0
How command byte and data byte map into MPR084's registers acknowledge from MPR084 S SLAVE ADDRESS R/W 0 A
COMMAND BYTE
A
DATA BYTE 1 byte
A
P
auto-increment memory word address
Figure 11. Command and Single Data Byte Received If multiple data bytes are transmitted before a STOP condition is detected, these bytes are generally stored in subsequent MPR084 internal registers because the command byte address generally auto-increments (Section 2.4).
2.3.7
Message Format for Reading the MPR084
The MPR084 is read using the MPR084's internally stored command byte as address pointer, the same way the stored command byte is used as address pointer for a write. The pointer generally auto-increments after each data byte is read using the same rules as for a write (Section 6.4.1). Thus, a read is initiated by first configuring the MPR084's command byte by performing a write (Figure 12). The master can now read `n' consecutive bytes from the MPR084, with the first data byte being read from the register addressed by the initialized command byte.
MPR084 Sensors Freescale Semiconductor Preliminary 7
When performing read-after-write verification, remember to re-set the command byte's address because the stored command byte address will generally have been auto-incremented after the write (Section 2.4).
acknowledge from MPR084 D15 D14 D13 D12 D11 D10 D9 D8 acknowledge from MPR084 D7 D6 D5 D4 D3 D2 D1 D0
How command byte and data byte map into MPR084's registers acknowledge from MPR084
S
SLAVE ADDRESS
1
A
COMMAND BYTE
A
DATA BYTE
A
P
R/W
n bytes auto-increment memory word address
Figure 12. `n' Data Bytes Received
2.3.8
Operation with Multiple Master
The application should use repeated starts to address the MPR084 to avoid bus confusion between I2C masters.On a I2C bus, once a master issues a start/repeated start condition, that master owns the bus until a stop condition occurs. If a master that does not own the bus attempts to take control of that bus, then improper addressing may occur. An address may always be rewritten to fix this problem. Follow I2C protocol for multiple master configurations.
2.3.9
Device Reset
The RST is an active-low software reset. This is implemented in the Configuration Register by activating the RST bit. When asserted, the device clears any transaction to or from the MPR084 on the serial interface and configures the internal registers to the same state as a power-up reset (Table 4). The MPR084 then waits for a START condition on the serial interface. The sensor controller is capable of operating down to 1.8 V, however, in order for the sensor controller to exit reset and startup correctly the host system must initially provide 2.0 V to 3.6 V input to VDD and then follow the process in Figure 13. This process is required in applications that require regulated operation in the 1.8 V to 2.0 V range. In the case that the application uses an unregulated battery, then the battery must initially provide at least 2.0 V to correctly power-up the sensor controller which limits battery selection to the 2.0 V to 3.6 V range.
Apply 2.0V to VDD Max To Sensor Controller
Idle Delay Loop
False
Established Comms with Sensor Controller? i.e. Read from FIFO Is Data valid? (0 x 40)
True
Lower VDD to the desired operating voltage 1.8 V to 2.0 V
Figure 13. Low Voltage (1.8 V - 2.0 V) Power-up Sequence
MPR084 Preliminary 8 Sensors Freescale Semiconductor
2.4
Register Address Map
The MPR084 is a peripheral that is controlled and monitored though a small array of internal registers which are accessed through the I2C bus. When communicating with the MPR084 each of the registers in Table 4 are used for specific tasks. The functionality of each specific register is detailed in the following sections.
Register FIFO Register Fault Register Touch Pad Status Register Touch Pad Configuration Register Sensitivity Threshold Registers 1 Sensitivity Threshold Registers 2 Sensitivity Threshold Registers 3 Sensitivity Threshold Registers 4 Sensitivity Threshold Registers 5 Sensitivity Threshold Registers 6 Sensitivity Threshold Registers 7 Sensitivity Threshold Registers 8 Electrode Channel Enable Mask Register Maximum Number of Touched Positions Register Master Tick Period Register Touch Acquisition Sample Period Register Sounder Configuration Register Low Power Configuration Register Stuck Key Timeout Register Configuration Register Sensor Information Register
Register Address 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14
Burst Mode Auto-Increment Address 0x00 0x02 0x00 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x00 0x14
MPR084 Sensors Freescale Semiconductor Preliminary 9
3
3.1
Touch Detection
Introduction
When using a capacitive touch sensor system the raw data must be filtered and interpreted. This process can be done many different ways but the method used in the MPR084 is explained in this chapter.
3.2
Understanding the Basics
The touch pad interface has to distinguish touch status through varying user conditions (different finger sizes in bare hands or gloves) and environmental conditions (electrical and RF noise, sensor contamination with dirt or moisture). The touch pad circuitry reports touch status as one of the following two conditions: 1. 2. Touch Pad untouched Touch Pad touched on one of eight pads.
The touch pad is only touched in one position, ideally near the middle of one of the eight pads. If a touch occurs between pads, untouched will be reported.
3.3
Conditional Output Scenarios
Since it is unlikely that in a real world case a single independent touch will occur two specific multi-touch response cases are outlined. Methods for changing the sensitivity of the device will be discussed in another Chapter, but the important part is that the sensitivity is determined by the strength of an input signal. If more than one input signal is above the selected sensitivity then the touch sensor controller interprets this in a specific way. This functionality is broken down into two different cases.
3.3.1
Simultaneous Touches
Any time multiple touches are detected at the same time the touch sensor controller recognizes this case and accounts for it. The number of allowed reported touches is settable using the Maximum Number of Touched Positions Register (Section 3.6). In the case where this register is set to 1, all touches past the first will be ignored and unreported. A special case is when exact 2 keys are involved in the interaction. In most cases one of the two electrodes will receive a stronger signal than the other. If the difference in capacitance is statistically significant between the pad with the stronger signal will be reported This functionality is sometimes called 1-Keyed Lockout. by changing the Maximum Number of Touched Positions Register (Section 3.6). this value can be set. Thus the n-key lockout is determined by this register.
3.3.2
Sequential Touches
Another case is when one touch pad is touched and held and a second touch pad is then touched and held. For this situation the second touch will be ignored and the first touch will continue to be reported. If the second touch is released before the first touch then the second touch will be completely ignored. But, if the first touch is released before the second then the system will report that the first key is released and that the second key is now touched. This functionality is sometimes called 2-Key Rollover.
3.4
Touch Pad Configuration Register
The Touch Pad Configuration Register configures a variety of the MPR084 features. Each of these features is described in following sections. The I2C slave address of the Touch Pad Configuration Register is 0x03. 7 R W Reset: TPE 1 6 0 5 BKA 0 4 ACE 0 3 TPRBE 0 2 TPTBE 0 1 0 0 TPE 1
0
0
= Unimplemented Figure 14. Touch Pad Configuration Register MPR084 Preliminary 10 Sensors Freescale Semiconductor
Table 4. Touch Pad Configuration Register Field Descriptions Field 7 TPSE Description Touch Pad Sounder Enable - The Touch Pad Sounder Enable bit controls if data is sent to the sounder. 0 Disable - Click Feedback Off 1 Enable - Click Feedback On Best Key Algorithm - The Best Key Algorithm, when enabled the Maximum Number of Touches register is ignored and the algorithm reports the single best key based upon the BKA algorithm and all electrodes that are decoding a touch. 0 BKA Disabled 1 BKA Enabled Auto Calibration Enable - The Auto Calibration Enable bit enables or disables the auto calibration function. 0 Disable 1 Enable Touch Pad Release Buffer Enable - The Touch Pad Release Buffer Enable bit determines whether or not data is logged in the FIFO when the touch pad transitions from a touched to untouched state. 0 Disable - No Release Data Logged 1 Enable - Release Data Logged Touch Pad Touch Buffer Enable - The Touch Pad Touch Buffer Enable bit determines whether or not data is logged in the FIFO any time a button is pressed. 0 Disable - Touches are not logged 1 Enable - Touches are logged Touch Pad Enable - The Touch Pad Enable bit enables or disables the touch sensor. When disabled, no touches are detected. 0 Disable - Touches not detected 1 Enable - Touches detected
5 BKA
4 ACE
3 TPRBE
2 TPTBE
0 TPE
3.5
Touch Acquisition Sample Period Register
The Touch Acquisition Sample Period Register is used to determine the electrode scan period of the system. The I2C slave address of the Touch Acquisition Sample Period Register is 0x0F. 7 R W Reset: 0 0 0 0 6 5 4 TASP 0 0 0 1 3 2 1 0
= Unimplemented Figure 15. Touch Acquisition Sample Period Register Table 5. Touch Acquisition Sample Register Field Description Field 7:0 TASP Description Touch Acquisition Sample Period - The Touch Acquisition Sample Period Field selects or reports the multiplication factor that is used to determine how often electrodes are scanned. The resulting factor must be in the range 1 to 32. If the value is outside of this range the TASP will be set to 00011111. 00000000 Encoding 0 - Sets the TASP multiplication factor to 1 ~ 00011111 Encoding 31 - Sets the TASP multiplication factor to 32
MPR084 Sensors Freescale Semiconductor Preliminary 11
3.6
Maximum Number of Touched Positions Register
The Maximum Number of Touched Positions Register adjusts the number of keys that can be concurrently reported as touched. The I2C slave address of the Maximum Number of Touched Positions Register is 0x0D. 7 R W Reset: 0 0 0 0 0 1 0 6 0 5 0 4 0 3 0 2 1 TPC 0 0 0
= Unimplemented Figure 16. Maximum Number of Touched Positions Registers Table 6. Maximum Number of Touched Positions Register Field Descriptions Field 2:0 TPC Description Touched Positions Count - The Touched Positions Count selects or reports the number of simultaneously reported touches. 000 Encoding 0 - Sets the number of allowed touches to 0 ~ 111 Encoding 7 - Sets the number of allowed touches to 7
3.7
Electrode Channel Enable Mask Register
The Electrode Channel Mask Register adjusts to the number of keys that are scanned by the MPR084. The I2C slave address of the Electrode Channel Mask Register is 0x0C. 7 R W Reset: E8EN 1 6 E7EN 1 5 E6EN 1 4 E5EN 1 3 E4EN 1 2 E3EN 1 1 E2EN 1 0 E1EN 1
= Unimplemented Figure 17. Electrode Channel Enable Mask Position Register Table 7. Electrode Channel Enable Mask Register Field Descriptions Field 7 E8EN Description Electrode 8 Enable - The Electrode 8 Enable bit enables or disables electrode number 8. 0 Electrode 8 Disable 1 Electrode 8 Enable Electrode 7 Enable - The Electrode 7 Enable bit enables or disables electrode number 7. 0 Electrode 7 Disable 1 Electrode 7 Enable Electrode 6 Enable - The Electrode 6 Enable bit enables or disables electrode number 6. 0 Electrode 6 Disable 1 Electrode 6 Enable Electrode 5 Enable - The Electrode 5 Enable bit enables or disables electrode number 5. 0 Electrode 5 Disable 1 Electrode 5 Enable
6 E7EN
5 E6EN
4 E5EN
MPR084 Preliminary 12 Sensors Freescale Semiconductor
Table 7. Electrode Channel Enable Mask Register Field Descriptions 3 E4EN Electrode 4 Enable - The Electrode 4 Enable bit enables or disables electrode number 4. 0 Electrode 4 Disable 1 Electrode 4 Enable Electrode 3 Enable - The Electrode 3 Enable bit enables or disables electrode number 3. 0 Electrode 3 Disable 1 Electrode 3 Enable Electrode 2 Enable - The Electrode 2 Enable bit enables or disables electrode number 2. 0 Electrode 2 Disable 1 Electrode 2 Enable Electrode 1 Enable - The Electrode 1 Enable bit enables or disables electrode number 1. 0 Electrode 1 Disable 1 Electrode 1 Enable
2 E3EN
1 E2EN
0 E1EN
MPR084 Sensors Freescale Semiconductor Preliminary 13
4
4.1
Modes of Operation
Introduction
The operating modes of the MPR084 are described in this section. Implementation and functionality of each mode are described. The Modes of Operation of the MPR084 combine to form a suite of quick response and low power consumption functionality. This is achieved through 2 Run modes and 2 Stop Modes. The two modes are enabled by toggling the Configuration Register's DCE and RUNE bits as shown in Table 8. Note that while in a run mode, the only register that can be written to is the Configuration Register. Thus, when changes to registers are needed, enter Stop1 mode, write to the registers and change the mode to "Run". Table 8. Mode Enable Register Bits Mode Run1 Run2 Stop1 Stop2 RUNE 1 1 0 0 DCE 1 0 1 0
4.2
Initial Power Up
On power-up, the interrupt output IRQ is reset, and IRQ will go high. The registers are reset to the values shown in Table 9. Table 9. Power-Up Register Configurations Register Function FIFO Register Fault Register Touch Pad Status Register Touch Pad Configuration Register Sensitivity Threshold Registers 1 Sensitivity Threshold Registers 2 Sensitivity Threshold Registers 3 Sensitivity Threshold Registers 4 Sensitivity Threshold Registers 5 Sensitivity Threshold Registers 6 Sensitivity Threshold Registers 7 Sensitivity Threshold Registers 8 Electrode Channel Enable Mask Register Maximum Number of Touched Positions Register Master Tick Period Register Touch Acquisition Sample Period Register Sounder Configuration Register Low Power Configuration Register Stuck Key Timeout Register Configuration Register Sensor Information Register MPR084 Preliminary 14 Sensors Freescale Semiconductor Power-Up Condition FIFO is empty No faults Touch Pad is untouched Touch Pad is enabled, without interrupts, with sounder enabled and Auto-Cal Disabled Maximum sensitivity Maximum sensitivity Maximum sensitivity Maximum sensitivity Maximum sensitivity Maximum sensitivity Maximum sensitivity Maximum sensitivity All channels enabled 4 maximum concurrent touched position allowed Master tick period is 10ms TASP is 1 master tick period Sounder is globally enabled, 10ms of 1kHz Low Power Mode is disabled Stuck key detector disabled Stop1 Mode. IRQ is disabled Fixed SensorInfo based on revision Register Address 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 HEX Value 0x40 0x00 0x00 0x81 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xFF 0x04 0x05 0x01 0x01 0x00 0x00 0x14 0xFF
4.3
Run1 Mode
When in Run1 mode the sensor controller will run continuously. During Run1 all the modules are synchronized by the Master Tick Period. This value can be set by using the Master Tick Period Register as outlined in the following section. While in this mode all functionality of the MPR084 is enabled; touch detection will occur, and I2C communication will be available. This mode is enabled by setting the Configuration Register's RUNE and DCE bits high.
4.3.1
Master Tick Period Register
The Master Tick Period Register is used to set the master tick of this system. All parts of the system are synchronized to this counter. This register is overridden in all modes except for Run1. When not in Run1 mode, the value of this register is ignored and 8ms is used for the primary clock. The I2C slave address of the Master Tick Period Register is 0x0E. 7 R W Reset: 0 0 0 0 6 5 4 MTP 0 1 0 1 3 2 1 0
= Unimplemented Figure 18. Master Tick Period Register Table 10. Master Tick Period Register Field Descriptions Field 7:0 Description Master Tick Period - The Master Tick Period selects or reports the current value of the touch sensor controller's primary clock. The resulting period must be in the range 5ms to 31ms. If the value is outside of this range the MTP will be set to 00011010. 00000000 Encoding 0 - Sets the primary clock multiplier to 5 ~ 00011010 Encoding 26 - Sets the primary clock multiplier to 31
MTP
4.4
Run2 Mode
When in Run2 mode the sensor controller will continue to scan the electrodes but a low power state will be enabled between each cycle. Because of this, any I2C communication that occurs, may or may not respond while the sensor is in this mode If DCE is enabled the sensor controller transitions between low power and active states. During the active part of the cycle communication with the sensor controller is possible; however, Freescale always requires users to issue an ATTN signal prior to initiating communications. Accessing the I2C interface while DCE mode is enabled without sending an ATTN signal first is likely to produce invalid data. This mode is enabled by setting the Configuration Register's RUNE bit high and DCE bit low. The only way to exit this mode is to toggle the Attention Pin, refer to Section 4.7.
4.5
Stop1 Mode
When in Stop1 mode the sensor controller will not scan the electrodes. While capacitance sensing is disabled I2C communications will still be accepted and the sensor controller will maintain instantaneous response to all register requests. This is the only mode in which register values can be set. This mode is enabled by setting the Configuration Register's RUNE bit low and DCE bit high.
4.6
Stop2 Mode
When in Stop2 mode the sensor controller will not scan the electrodes or accept I2C communication. The MPR084 is off during this mode. This mode is enabled by setting the Configuration Register's RUNE bit low and DCE bit low. The only way to exit this mode is to toggle the Attention Pin, refer to Section 4.7.
MPR084 Sensors Freescale Semiconductor Preliminary 15
4.7
Configuration Register
The Configuration Register allows a user to reset the part, adjust Interrupt settings, and change the mode. The I2C slave address of the Configuration Register is 0x13. 7 R W Reset: 0 0 6 RST 0 1 5 4 3 0 2 DCE 1 1 IRQEN 0 0 RUNE 0
0
= Unimplemented Figure 19. Configuration Register Table 11. Configuration Register Field Descriptions Field 7:5 IRQR Description Interrupt Rate - The Interrupt Rate Field selects the amount to multiply the MTP by to determine the minimum delay between sequential Interrupts. 000 Encoding 0 - Sets the IRQR multiplication factor to 1 ~ 111 Encoding 7 - Sets the IRQR multiplication factor to 8 Reset - Asserts a global reset of the sensor controller. 0 Reset Asserted 1 Reset Not Asserted Duty Cycle Enable - The Duty Cycle Enable bit enables or disables duty cycling on the MPR084. This bit is active low. 0 Duty Cycle Enabled (2 modes) 1 Duty Cycle Disabled (1 modes) Interrupt Enable - The Interrupt Enable bit enables or disables the IRQ Functionality. 0 IRQ Disabled 1 IRQ Enabled Run Mode Enable - The Run Mode Enable bit enables or disables scanning of the electrodes for touch detection. This bit is active high. 0 Electrode Scanning Disabled (Stop modes) 1 Electrode Scanning Enabled (Run modes)
4 RST 2 DCE
1 IRQEN
0 RUNE
4.8
Attention Pin
The Attention (ATTN) pin allows a user to externally set the Configuration Register's DCE bit high. This is latched on a high to low transition. Since the current mode of the device is enabled through the DCE this will cause duty cycling to be disabled and change the current mode from Run2 to Run1, or Stop2 to Stop1 (depending on the previous state). When in Run2 or Stop2 modes this is the only way to enable the I2C communication.
MPR084 Preliminary 16 Sensors Freescale Semiconductor
5
5.1
Low Power Configuration
Introduction
The MPR084 features a Low Power mode that can reduce the power consumption into the microamps range. This feature can be used to both adjust the response time of the system, and change the conditions on which Low Power would be enabled.
5.2
Operation
This Low Power configuration is only active when the sensor controller is in Run2 mode. The Low Power mode decreases current consumption by increasing the response time of the MPR084. This increase is controlled through two factors. During normal Run2 operation of the sensor controller the Max Response Time (MRT) is calculated by taking the product of the TASP and the primary clock. From Chapter 4 the primary clock is the (MTP + 5) ms. Since the sensor controller is in Run2, the primary clock is also multiplied by a factor of 8. The debounce rate of the MPR084 is 4 times the sample rate thus the MRT is represented by the following equation.
MTP + 5 MRT 1 = --------------------- + 1 x TASP x 4 x 8ms 8
Equation 1
First, the Idle Interface Timeout (IIT) represents the total time the touch interface should remain idle before going into Low Power mode. This value can be calculated by taking the product of the ITP, TASP and primary clock (8ms) with a factor of 64. Thus the IIT is represented as follows:
MTP + 5 MRT 2 = --------------------- + 1 x TASP x SCD x 4 x 8 ms 8
Equation 2
Second, the Max Response Time (MRT) represents the total time the touch interface should remain inactive before scanning the electrodes. This value can be calculated by taking the product of the SCD, TASP and primary clock (8ms) with a factor of 5. Thus the MRT is represented as follows:
MTP + 5 ITT = --------------------- + 1 x TASP x ITP x 6 x 8ms 8
Equation 3
When in Run2 mode, the sensor controller will initially scan the electrodes at the rate of MRT1. When scanning at MRT1 and the touch interface remains idle for the IIT period then the scan period will change to MRT2. When scanning at MRT2 and a touch is detected the scan rate will transition back to MRT1.
LP DISABLED
run2 SET
MRT1
ITT PERIOD
MRT2
TOUCH DETECTED
Figure 20. Low Power Scan Period Transition Diagram
5.3
Configuration
Low Power Configuration is achieved through setting two values; the Idle Timeout Period and the Sleep Cycle Duration. This functionality is described in the following section.
MPR084 Sensors Freescale Semiconductor Preliminary 17
5.3.1
Low Power Configuration Register
The Low Power Configuration register is used to set both the Idle Timeout Period and Sleep Cycle Duration multiplication factors. The I2C slave address of the Low Power Configuration Register is 0x11. 7 R W Reset: 0 6 ITP 0 0 0 0 5 4 3 2 SCD 0 0 0 1 0
= Unimplemented Figure 21. Low Power Configuration Register Table 12. Low Power Configuration Register Field Descriptions Field 7:5 ITP Description Idle Timeout Period - The Idle Timeout Period selects the amount to multiply the TASP (touch acquisition sample period) by to determine the idle interface timeout (IIT) period of the sensor controller. 000 Encoding 0 - Disables Low Power Mode 001 Encoding 1 - Sets the ITP multiplication factor to 1 ~ 111 Encoding 7 - Sets the ITP multiplication factor to 7 Sleep Cycle Duration - The Sleep Cycle Duration Field selects the amount to multiply the TASP (touch acquisition sample period) by to determine the Sleep period of the sensor controller. 00000 Encoding 0 - Disables Low Power Mode 00001 Encoding 1 - Sets the SCD multiplication factor to 1 ~ 11111 Encoding 31 - Sets the SCD multiplication factor to 31
4:0 SCD
MPR084 Preliminary 18 Sensors Freescale Semiconductor
6
6.1
Output Mechanisms
Introduction
The MPR084 has three primary methods for reporting data in addition to an IRQ output that is described in Chapter 7. The three output systems are described in this section.
6.2
Instantaneous
The Instantaneous output shows the current status of the user interface. This information is displayed in terms of the current touched pad position that is touched. Only one touch can be shown at a time.
6.2.1
Touch Pad Status Register
The Touch Pad Status Register is a read only register for determining the current status of the touch pad. The I2C slave address of the Touch Pad Status Register is 0x02. 7 R W Reset: 0 0 0 0 0 0 0 0 E8S 6 E7S 5 E6S 4 E5S 3 E4S 2 E3S 1 E2S 0 E1S
= Unimplemented Figure 22. Touch Pad Status Register Table 13. Touch Pad Status Register Field Descriptions Field 7 E8S 6 E7S 5 E6S 4 E5S 3 E4S 2 E3S 1 E2S 0 E1S Description Electrode 8 Status - The Electrode 8 Status bit shows whether or not electrode 8 is touched. 0 Electrode 8 untouched 1 Electrode 8 touched Electrode 7 Status - The Electrode 7 Status bit shows whether or not electrode 7 is touched. 0 Electrode 7 untouched 1 Electrode 7 touched Electrode 6 Status - The Electrode 6 Status bit shows whether or not electrode 6 is touched. 0 Electrode 6 untouched 1 Electrode 6 touched Electrode 5 Status - The Electrode 5 Status bit shows whether or not electrode 5 is touched. 0 Electrode 5 untouched 1 Electrode 5 touched Electrode 4 Status - The Electrode 4 Status bit shows whether or not electrode 4 is touched. 0 Electrode 4 untouched 1 Electrode 4 touched Electrode 3 Status - The Electrode 3 Status bit shows whether or not electrode 3 is touched. 0 Electrode 3 untouched 1 Electrode 3 touched Electrode 2 Status - The Electrode 2 Status bit shows whether or not electrode 2 is touched. 0 Electrode 2 untouched 1 Electrode 2 touched Electrode 1 Status - The Electrode 1 Status bit shows whether or not electrode 1 is touched. 0 Electrode 1 untouched 1 Electrode 1 touched
MPR084 Sensors Freescale Semiconductor Preliminary 19
6.3
Buffered
The Buffered output is done through a FIFO. The FIFO will buffer every touch that occurs up to 30 values before the buffer overflows and data is lost. Any time data is read from the FIFO it is pulled from the buffer and the next item becomes available. The buffer can be cleared (NDF goes high) by either reading the last entry or attempting to write to the register. The buffer settings are configured in the Touch Pad Configuration Register as described in Section 3.4.
6.3.1
FIFO Register
The FIFO Register is a read only register for determining the current status of the touch pad. Any time a write is issued to this register the buffer will be cleared. The I2C slave address of the FIFO Register is 0x00. 7 R W Reset: 0 1 0 0 0 0 0 0 MDF 6 NDF 5 OF 4 TRF 3 2 BP 1 0
= Unimplemented Figure 23. FIFO Register Table 14. FIFO Register Field Descriptions Field 7 MDF Description More Data Flag - The More Data Flag shows whether or not data will remain in the buffer after the current read. 0 No Data Remaining 1 Data Remaining No Data Flag - The No Data Flag shows whether or not there is currently data in the buffer. 0 Buffer currently has data 1 Buffer does not currently have data Overflow Flag - The Overflow Flag shows whether or not an overflow has occurred. If this flag is high then the most current data was lost. 0 No Overflow has occurred 1 Overflow has occurred Touch Release Flag - The Touch Release Flag shows if the current buffer entry is a touch or release of a pad. 0 Pad is released 1 Pad is touched Buffered Position - The Buffered Position represents the electrode number that is currently being displayed by the buffer. 0000 Encoding 0 - Buffered touch of electrode 1 ~ 0111 Encoding 7 - Buffered touch of electrode 8
6 NDF
5 OF
4 TRF
3:0 BP
6.4
Error
The MPR084 can generate a fault under two conditions; an electrode is shorted to VDD, or an electrode is shorted to VSS. Once a fault is asserted the sensor electrodes will no longer be scanned until the fault is cleared. In the event of multiple faults occurring at the same time, the sensor controller will report the first fault that is detected during scanning. In addition to the VDD or VSS short, there is also a fault for when too many keys have been touched. The Max Number of Keys Exceeded status bit is an instantaneous output that is high when more keys are pressed than allowed by the TPC (Section 3.6).
MPR084 Preliminary 20 Sensors Freescale Semiconductor
6.4.1
Fault Register
The Fault Register is a read only register that shows the fault number under the current sensor conditions. Any write to the Fault Register will clear the register, when in Stop mode. The Fault register cannot be cleared when the part is in a Run mode. The I2C slave address of the Fault Register is 0x01. 7 R W Reset: 0 0 0 0 0 0 0 0 0 6 0 5 0 4 0 3 0 2 MNKE 1 FAULT 0
= Unimplemented Figure 24. Fault Register Table 15. Fault Register Field Descriptions Field 2 MNKE Description Maximum Number of Keys Exceeded - The Maximum Number of Keys Exceeded status bit indicates whether or not more keys than allowed are currently being touched. 1 TPC Exceeded 0 TPC Not Exceeded Fault - The Fault code represents the currently asserted fault condition. 00 Encoding 0 - No fault detected 01 Encoding 1 - Short to VSS detected 10 Encoding 2 - Short to VDD detected
1:0 FAULT
MPR084 Sensors Freescale Semiconductor Preliminary 21
7
7.1
Interrupts
Introduction
The MPR084 has one interrupt output that is configured by registers and alerts the application when a touch or fault is detected. When running in Run2 or Stop2 mode where I2C communication is not available this feature alerts the user to sensor touches.
7.2
Condition for Interrupt
There are two cases that latch the Interrupt buffered data available or fault detected.
7.2.1
Buffered Data Available
The interrupt for Buffered Data Available will only trigger when the NDF (No Data Flag) transitions from high to low. This signifies that there is new data available in the buffer. The interrupt is deasserted on the first read/write of the FIFO Register and cannot be reasserted for buffered data until the FIFO is empty (either by reading all the data, or clearing the buffer).
7.2.2
Fault Detected
The interrupt for a Fault Detected condition is triggered any time the Fault condition in the Fault Register transitions from zero to non-zero. The interrupt is deasserted when the Fault Register is cleared (by writing to the Fault Register).
7.3
Settings
Interrupts are configured through I2C using the Configuration Register (Section 4.7). Two of the settings in this register will affect the interrupt functionality. The Interrupt Enable (IRQEN) must be set high for the IRQ to be enabled. When low, all interrupts will be ignored, and the IRQ pin will never latch. The Interrupt Rate (IRQR) sets the minimum delay between sequential triggered interrupts. The minimum interrupt period can be calculated by taking the product of the MCP (master clock period) and IRQR with a factor of 4. Thus, for the minimum setting an interrupt would be triggered no more often than 4 times the sensor scan rate.
MinInterruptPeriod ( ms ) = MCP x IRQR x 4
If the MPR084 is using Run2, the minimum interrupt period would be represented by the following equation.
Equation 4
MTP + 5 MinInterruptPeriod ( ms ) = --------------------- + 1 x 8 x I RQR x 4 8 7.4 IRQ Pin
Equation 5
The IRQ pin is an open-drain, latching interrupt output which requires an external pull-up resistor. The pin will latch down based on the conditions in Section 6.2. The pin will reset when an I2C transmission reads/writes the appropriate register displaying information about the source of the interrupt. Thus if the source is buffered data available then a FIFO Buffer read/write will clear the IRQ pin. If the source is a fault detected then a write of the Fault Register will clear the pin.
MPR084 Preliminary 22 Sensors Freescale Semiconductor
7.4.1
IRQ Pin Timing
The MinInterruptPeriod is implemented as a hold off of IRQ latching per Figure 25 and Figure 26. In the first case the MinInterruptPeriod is longer than the interval between sequential interrupt source events, thus it delays the IRQ from latching until the MinInterruptPeriod has elapsed. In the second case the MinInterruptPeriod is shorter than the interval between sequential interrupt source events, thus the IRQ latches as it normally would without additional delay.
Initial Interrupt Event
Second Interrupt Event MinInterruptPeriod
IRQ
Figure 25. IRQ Timing Diagram - Case 1
Initial Interrupt Event IRQ
Second Interrupt Event MinInterruptPeriod
Figure 26. IRQ Timing Diagram - Case 2
MPR084 Sensors Freescale Semiconductor Preliminary 23
8
8.1
Calibration
Introduction
The MPR084 is self-calibrating. This is done both at initial start-up of the device and during run time.
8.2
Initial Start-up Conditions
Initial calibration of the MPR084 occurs every time the device resets. The first key detection cycle is used as a baseline capacitance value for all remaining calculations. Thus, a touch is detected by taking the difference between this baseline value and the current capacitance on the electrode.
8.3
Auto-Calibration
The MPR084 has an auto-calibration feature. This is enabled through the Touch Pad Configuration Register (Section 3.4), by setting the ACE bit high. Auto calibration is done by two mechanisms. The basic auto-calibration will recalculate the baseline value after 6 sample periods. Thus the auto calibrate period can be calculate by multiplying the master clock period (in milliseconds) and the touch acquisition sample period with a factor of 64.
AutoCalibrationPeriod ( ms ) = MCP x TASP x 64
Equation 6
If a touch is currently being detected the auto-calibration will not engage and calibration will be ignored. The device can also be calibrated when a key is being touched, this is controlled by stuck key detection.
8.4
Stuck Key Detection
The Stuck Key Detection system allows the application to specify the maximum amount of time a touch should be detected before it is calibrated into the baseline and the touch is ignored. This is controlled by setting the Stuck Key Timeout multiplication factor (SKT). The timeout period can be calculated by multiplying the SKT, master clock period (in ms) and touch acquisition sample period with a factor of 64.
AutoCalibrationPeriod ( ms ) = MCP x TASP x SKT x 64
Equation 7
When Stuck Key Detection is off a touched key will remain touched indefinitely and never be calibrated into the baseline value.
8.4.1
Stuck Key Timeout Register
The Stuck Key Timeout Register is used to determine the electrode scan period of the system. The I2C slave address of the Stuck Key Timeout Register is 0x12. 7 R W Reset: 0 0 0 0 6 5 4 SKT 0 0 0 0 3 2 1 0
= Unimplemented Figure 27. Stuck Key Timeout Register Table 16. Stuck Key Timeout Register Field Descriptions Field 7:0 SKT Description Stuck Key Timeout - The Stuck Key Timeout field selects or reports the multiplication factor that is used to determine how often electrodes are calibrated while a touch is being detected. 00000000 Encoding 0 - Turns off Stuck Key Detection 00000001 Encoding 1 - Sets the SKT multiplication factor to 2 ~ 11111111 Encoding 255 - Sets the SKT multiplication factor to 256
MPR084 Preliminary 24 Sensors Freescale Semiconductor
9
9.1
Sensitivity
Introduction
The MPR084 can operate in a variety of environments with a variety of different electrode patterns. Because of this it is necessary to adjust the relative sensitivity of the sensor controller. Usually this requires fine tuning in any final application. There are many factors that must be taken into account, but much of the time this value is relative to the capacitance changes generated by a touch. Since capacitance is directly proportional to the dielectric constant of the material and the area of the pad, while inversely proportional to the distance between pads these are the primary factors.
ke 0 A C = ----------d
Equation 8
As the relative capacitance rises the sensitivity setting of the MPR084 should be adjusted accordingly. Thus a very high sensitivity value represents a large A and a small d.
9.2
Adjusting the Sensitivity
The sensitivity of the MPR084 is adjusted by varying the Sensitivity Threshold Registers.
9.2.1
Sensitivity Threshold Registers
The Sensitivity Threshold registers all sensitivity of the MPR084 to be adjusted for any situation. The I2C slave address of the Sensitivity Threshold Registers is 0x04 - 0x0B. 7 R W Reset: 0 0 0 0 6 5 4 SL 0 0 0 0 3 2 1 0
= Unimplemented Figure 28. Sensitivity Threshold Register Format Table 17. Sensitivity Threshold Register Format Descriptions Field 7:0 ST Description Sensitivity Threshold - The Sensitivity Threshold selects or reports the sensitivity setting of the Sensor Controller. The resulting value must be in the range 1 to 64 units. If the value is outside of this range the ST will be set to 00111111. 00000000 Encoding 0 - Sets the sensitivity to level 1 ~ 00111111 Encoding 63 - Sets the sensitivity to level 64
MPR084 Sensors Freescale Semiconductor Preliminary 25
10
10.1
Additional Features
Key Click Sound Generator
The Key Click Sound Generator allows the MPR084 to generate audible feedback, independent of the I2C communication status. The sounder is used to drive a piezo buzzer. This output is configured by using the Sounder Register, shown in the following section.
10.1.1 Sounder Configuration Register
The I2C slave address of the Sounder Configuration Register is 0x07 - 0x10 7 R W Reset: 0 0 0 0 0 0 6 0 5 0 4 0 3 0 2 CP 0 1 FREQ 0 0 SEN 1
= Unimplemented Figure 29. Sounder Configuration Register Table 18. Sounder Configuration Register Field Descriptions Field 2 CP 1 FREQ 0 SEN Description Click Period - The Click Period bit controls the length of the sounder click. 0 Sounder Click Period is 10ms 1 Sounder Click Period is 20ms Frequency - The Frequency bit controls the frequency of the driven output. 0 Sounder frequency is 1kHz 1 Sounder frequency is 2kHz Sounder Enable - The Sounder Enable bit enables or disables the sounder output. 0 Disable 1 Enable
10.2
Sensor Information
The Sensor Information register is a read only register that displays a descriptor which contains static information about the MPR084 version.
10.2.1 Sensor Information Register
The I2C slave address of the Sensor Information Register is 0x14. 7 R W Reset: 0 1 0 0 0 1 1 0 6 5 4 3 2 1 0
SensorInfo
= Unimplemented Figure 30. Sensor Information Register Table 19. Sensor Information Register Field Descriptions Field 7-0 SensorInfo Description SensorInfo - The Sensor Information register describes the version information for the part. Burst reads will display ASCII data in the following format: VENDOR_LABEL",PN:"PRODUCT_LABEL",QUAL:"BUILD_TYPE_LABEL",VER:" BUILD_VERSION_MAJOR"_"BUILD_VERSION_MINOR"_"BUILD_NUMBER"\0"
MPR084 Preliminary 26 Sensors Freescale Semiconductor
Appendix A Electrical Characteristics
A.1 Introduction
This section contains electrical and timing specifications.
A.2
Absolute Maximum Ratings
Absolute maximum ratings are stress ratings only, and functional operation at the maxima is not guaranteed. Stress beyond the limits specified in Table A-1 may affect device reliability or cause permanent damage to the device. For functional operating conditions, refer to the remaining tables in this section. This device contains circuitry protecting against damage due to high static voltage or electrical fields; however, it is advised that normal precautions be taken to avoid application of any voltages higher than maximum-rated voltages to this high-impedance circuit. Table 20. Absolute Maximum Ratings - Voltage (with respect to VSS) Rating Supply Voltage Input Voltage SCL, SDA, AD0, IRQ, ATTN, SOUNDER Operating Temperature Range Storage Temperature Range Symbol VDD VIN Value -0.3 to +3.8 VSS - 0.3 to VDD + 0.3 Unit V V
TSG TSG
-40 to +85 -55 to +150
C C
A.3
ESD and Latch-up Protection Characteristics
Normal handling precautions should be used to avoid exposure to static discharge. Qualification tests are performed to ensure that these devices can withstand exposure to reasonable levels of static without suffering any permanent damage. During the device qualification ESD stresses were performed for the Human Body Model (HBM), the Machine Model (MM) and the Charge Device Model (CDM). A device is defined as a failure if after exposure to ESD pulses the device no longer meets the device specification. Complete DC parametric and functional testing is performed per the applicable device specification at room temperature followed by hot temperature, unless specified otherwise in the device specification. Table 21. ESD and Latch-up Test Conditions Rating Human Body Model (HBM) Machine Model (MM) Charge Device Model (CDM) Latch-up current at TA = 85C Symbol VESD VESD VESD ILATCH Value 2000 200 500 100 Unit V V V mA
MPR084 Sensors Freescale Semiconductor Preliminary 27
A.4
DC Characteristics
This section includes information about power supply requirements and I/O pin characteristics. Table 22. DC Characteristics (Temperature Range = -40C to 85C Ambient)
(Typical Operating Circuit, VDD = 1.8 V* to 3.6 V, TA = TMIN to TMAX, unless otherwise noted. Typical current values are at VDD = 3.3 V, TA = +25C.)
Parameter Operating Supply Voltage Run1 mode Current Run2 mode Current Stop1 mode Current Stop2 mode Current Input High Voltage SDA, SCL Input Low Voltage SDA, SCL Input Leakage Current SDA, SCL Input Capacitance SDA, SCL Output Low Voltage SDA, IRQ
Symbol VDD Irun1 Irun2 Istop1 Istop2 VIH VIL IIH, IIL
Conditions VDD = 1.8 V VDD = 1.8 V VDD = 1.8 V VDD = 1.8 V
Min 1.8*
Typ 1.62 41 1.74 2
Max 3.6
Units V mA A mA A V
0.7 x VDD 0.35 x VDD 0.025 1 7
V A pF V
VOL
IOL = 6mA
0.5V
*The MPR084 requires a specific start-up sequence for VDD< 2.0 V. Refer to Section 2.3.9.
A.5
I2C AC Characteristics
This section includes information about I2C AC Characteristics. Table 23. I2C AC Characteristics
(Typical Operating Circuit, V+ = 1.8 V to 3.6 V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at V+ = 3.3 V, TA = +25C.)
Parameter Serial Clock Frequency Capacitive Load for Each Bus Line 1. Clock Stretching is required for reliable communications
(1)
Symbol fSCL Cb
Conditions
Min
Typ
Max 100 400
Units kHz pF
MPR084 Preliminary 28 Sensors Freescale Semiconductor
Appendix B Brief Register Descriptions
FIFO Register: 0x00
7 R W Reset: 0 1 0 0 0 0 0 0 MDF 6 NDF 5 OF 4 TRF 3 2 BP 1 0
= Unimplemented
Fault Register: 0x01
7 R W Reset: 0 0 0 0 0 0 0 0 0 6 0 5 0 4 0 3 0 2 MNKE 1 FAULT 0
= Unimplemented
Touch Pad Status Register: 0x02
7 R W Reset: 0 0 0 0 0 0 0 0 E8S 6 E7S 5 E6S 4 E5S 3 E4S 2 E3S 1 E2S 0 E1S
= Unimplemented
Touch Pad Configuration Register: 0x03
7 R W Reset: TPE 1 6 0 5 BKA 0 4 ACE 0 3 TPRBE 0 2 TPTBE 0 1 0 0 TPE 1
0
0
= Unimplemented
Sensitivity Threshold Registers: 0x04
7 R W Reset: 0 0 0 0 6 5 4 SL 0 0 0 0 3 2 1 0
= Unimplemented
MPR084 Sensors Freescale Semiconductor Preliminary 29
Master Tick Period Register: 0x05
7 R W Reset: 0 0 0 0 6 5 4 MTP 0 1 0 1 3 2 1 0
= Unimplemented
Touch Acquisition Sample Period Register: 0x06
7 R W Reset: 0 0 0 0 6 5 4 TASP 0 0 0 1 3 2 1 0
= Unimplemented
Sounder Configuration Register: 0x07
7 R W Reset: 0 0 0 0 0 0 6 0 5 0 4 0 3 0 2 CP 0 1 FREQ 0 0 SEN 1
= Unimplemented
Low Power Configuration Register: 0x08
7 R W Reset: 0 6 ITP 0 0 0 0 5 4 3 2 SCD 0 0 0 1 0
= Unimplemented
Stuck Key Timeout Register: 0x09
7 R W Reset: 0 0 0 0 6 5 4 SKT 0 0 0 0 3 2 1 0
= Unimplemented
Sensor Information Register: 0x14
7 R W Reset: 0 1 0 0 0 1 1 0 6 5 4 3 2 1 0
SensorInfo
= Unimplemented
MPR084 Preliminary 30 Sensors Freescale Semiconductor
Configuration Register: 0x0A
7 R W Reset: 0 0 6 RST 0 1 5 4 3 0 2 DCE 1 1 IRQEN 0 0 RUNE 0
0
= Unimplemented
Electrode Channel Enable Mask Register: 0x0C
7 R W Reset: E8EN 1 6 E7EN 1 5 E6EN 1 4 E5EN 1 3 E4EN 1 2 E3EN 1 1 E2EN 1 0 E1EN 1
= Unimplemented
Maximum Number of Touched Positions Register: 0x0D
7 R W Reset: 0 0 0 0 0 1 0 6 0 5 0 4 0 3 0 2 1 TPC 0 0 0
= Unimplemented
MPR084 Sensors Freescale Semiconductor Preliminary 31
Appendix C Ordering Information
C.1 Ordering Information
This section contains ordering information for MPR084Q and MPR084EJ devices. ORDERING INFORMATION Device Name MPR084Q MPR084EJ -40C to +85C Temperature Range Case Number 1679 (16-Lead QFN) 948F (16-Lead TSSOP) Touch Pads
8-pads
C.2
Device Numbering Scheme
All Proximity Sensor Products have a similar numbering scheme. The below diagram explains what each part number in the family represents.
M
Status (M = Fully Qualified, P = Preproduction) Proximity Sensor Product Number of Electrodes (08 = 8 electrode device)
PR EE
X
P
Package Designator (Q = QFN, EJ = TSSOP) Version
MPR084 Preliminary 32 Sensors Freescale Semiconductor
PACKAGE DIMENSIONS
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PACKAGE DIMENSIONS
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MPR084 Preliminary 38 Sensors Freescale Semiconductor
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