sensor solutions /// meas HTU21D xplained pro board 062017 page 1 meas HTU21D xplained pro board digital humidity digital component sensor (dcs) development tools the HTU21D xplained pro provides the necessary hardware to interface the HTU21D digital relative humidity and temperature sensor to any system that utilizes xplained pro compatible expansio n ports configurable for i 2 c communication. the HTU21D sensor is a self- contained humidity and temperature sensor that is fully calibr ated during manufacture. the sensor can operate from 1.5v to 3.6v, has selectable resolution, low battery detect, and checksum capabi lity. the HTU21D has a low power stand-by mode for power-sensitive applications. refer to the HTU21D datasheet for detailed information regarding operation of the ic: http://www.te.com/usa-en/product-cat-hsc0004.html specifications ? measures relative humidity from 0% to 100% ? measures temperature from -40c to 125c ? i 2 c communication ? fully calibrated ? fast response time ? selectable resolution ? very low power consumption performance ? 0% to 100% relative humidity range ? -40c to 125c temperature range ? very low power consumption ? operates from 1.5v to 3.6v ? fast response time C 5 seconds typical ? built-in heater for fast recovery from saturation ? recovers fully from condensation ? fast conversion time C 14ms typical features ? 20 -pin xplained pro compatible connector ? i 2 c interface ? xplained pro hardware identification chip ? atmel studio 6 project available for download ? c c code available for download ? selectable 8-12 bit resolution for humidity ? selectable 12-14 bit resolution for temperature schematic
meas HTU21D xplained pro board digital humidity dcs development tools sensor solutions /// meas HTU21D xplained pro board 0 62017 page 2 connector pin assignments (i 2 c communications) system plug dimensions (mm) detailed description i 2 c interface the peripheral module can interface to the host being plugged di rectly into an xplained pro extension port (configured for i 2 c) through connector jp1. external control signals the ic operates as an i 2 c slave using the standard 2 wire i 2 c connection scheme. the ic is controlled either by the host (through the xplained pro connector). in cases where one or more of th e scl and sda signals are driven from an external source, 10k resistors r1, r2 provide pull-up. however, this also in creases the apparent load to the external driving source. if the external source is not capable of driving these loads (10k ), they should be removed. reference materials the complete software kit is available for download at: link t o HTU21D_cproj.zip connector jp1 pin no. signal description pin no. signal description 1 id hardware identification 11 sda twi serial data 2 gnd ground 12 scl twi serial clock 3 n/c not connected 13 n/c not connected 4 n/c not connected 14 n/c not connected 5 n/c not connected 15 n/c not connected 6 n/c not connected 16 n/c not connected 7 n/c not connected 17 n/c not connected 8 n/c not connected 18 n/c not connected 9 n/c not connected 19 gnd ground 10 n/c not connected 20 vdd power supply
meas HTU21D xplained pro board digital humidity dcs development tools sensor solutions /// meas HTU21D xplained pro board 0 62017 page 3 drivers & software detailed example software and drivers are available that execute d irectly without modification on a number of development boards that support an integrated or synthesized microprocesso r. the download contains several source files intended to accelerate customer evaluation and design. the source code is wri tten in standard ansi c format, and all development documentation including theory/operation, register description, and function prototypes are documented in the interface file. functions summary enumerations enum htu21_i2c_master_mode { htu21_i2c_hold , htu21_i2c_no_hold } enum htu21_status { htu21_status_ok , htu21_status_no_i2c_acknowledge , htu21_status_i2c_transfer_error , htu21_status_crc_error } enum htu21_resolution { htu21_resolution_t_14b_rh_12b = 0, htu21_resolution_t_12b_rh_8b , htu21_resolution_t_13b_rh_10b , htu21_resolution_t_11b_rh_11b } enum htu21_battery_status { htu21_battery_ok , htu21_battery_low } enum htu21_heater_status { htu21_heater_off , htu21_heater_on } functions void htu21_init (void) configures the sercom i2c master to be used with the htu21 device. bool htu21_is_connected (void) reset the htu21 device. enum htu21_status htu21_reset (void) reset the htu21 device. enum htu21_status htu21_read_serial_number (uint64_t *) reads the htu21 serial number. enum htu21_status htu21_set_resolution (enum htu21_resolution) set temperature and humidity adc resolution. void htu21_set_i2c_master_mode (enum htu21_i2c_master_mode) set i2c master mode. this determines whether the program will hold while adc is accessed or will wait some time. enum htu21_status htu21_read_temperature_and_relative_humidity (float *, float *) reads the relative humidity value. enum htu21_status htu21_get_battery_status (enum htu21_battery_status *) provide battery status. enum htu21_status htu21_enable_heater (void) enable heater. enum htu21_status htu21_disable_heater (void) disable heater. enum htu21_status htu21_get_heater_status (enum htu21_heater_status *) get heater status. float htu21_compute_compensated_humidity (float, float) returns result of compensated humidity. float htu21_compute_dew_point (float, float) returns the computed dew point.
meas HTU21D xplained pro board digital humidity dcs development tools sensor solutions /// meas HTU21D xplained pro board 0 62017 page 4 project setup this project is based on atsamd20j18 board with measurement special ties xplained pro extension board connected to ext1 pad as shown on figure below. running the application 1. download the HTU21D xplained pro example package on te website 2. decompress the archive file 3. open the .cproj project file with atmel studio 6 4. you will now be able to build the HTU21D example project - 5. finally, run the build result on your xplained pro board - application code this section is intended to provide a basic example of functiona lity. /** * \file main.c * * \brief htu21 temperature & humidity monitoring appl ication file * * copyright (c) 2014 measurement specialties. all rights reserved. * */ #include uint64_t serial; float temperature; float relative_humidity; float compensated_humidity; float dew_point; enum htu21_heater_status heater; int main ( void )
meas HTU21D xplained pro board digital humidity dcs development tools sensor solutions /// meas HTU21D xplained pro board 0 62017 page 5 { enum htu21_status status; float last_temperature = 0 ; float variation = 0 ; uint8_t n= 0 ; system_init (); delay_init (); // configure device and enable htu21_init (); if ( ! htu21_is_connected () ) return -1 ; // reset htu21 status = htu21_reset (); if ( status != htu21_status_ok) return -1 ; // read serial number status = htu21_read_serial_number (&serial); if ( status != htu21_status_ok) return -1 ; // configure resolution status = htu21_set_resolution (htu21_resolution_t_12b_rh_8b); if ( status != htu21_status_ok) return -1 ; // monitor temperature every 500ms while ( 1 ) { // enable heater for 10s if ( (n== 10 ) ) { status = htu21_enable_heater (); if ( status != htu21_status_ok) return -1 ; } // disable heater after 20s if ( (n== 20 ) ) { status = htu21_disable_heater (); if ( status != htu21_status_ok) return -1 ; } // check heater status status = htu21_get_heater_status (&heater); if ( status != htu21_status_ok)
meas HTU21D xplained pro board digital humidity dcs development tools sensor solutions /// meas HTU21D xplained pro board 0 62017 page 6 return -1 ; // alternate between w and w/o hold temperature rea d if ( n& 1 ) htu21_set_i2c_master_mode (htu21_i2c_no_hold); else htu21_set_i2c_master_mode (htu21_i2c_hold); status = htu21_read_temperature_and_relative_humidity (&temperature, &relative_humidity); if ( status != htu21_status_ok) return -1 ; compensated_humidity = htu21_compute_compensated_humidity (temperature,relative_humidity); dew_point = htu21_compute_dew_point (temperature,relative_humidity); variation += temperature - last_temperature; // look for significant temperature variation if ( variation >= 0.5 ) { // yes, so turn led on. port_pin_set_output_level (led_0_pin, led_0_active); variation = 0 ; } else if ( variation <= -0.5 ) { // no, so turn led off. port_pin_set_output_level (led_0_pin, led_0_inactive); variation = 0 ; } delay_ms ( 500 ); last_temperature = temperature; n++; if (n== 50 ) n= 0 ; } return 0 ; }
meas HTU21D xplained pro board digital humidity dcs development tools sensor solutions /// meas HTU21D xplained pro board 0 62017 page 7 ordering information description part number meas HTU21D xplained pro board dpp301a000 product sheet meas france sas, a te connectivity company. tel:+33 (0) 800 - 440 - 5100 email: customercare.tlse@te.com te.com/sensorsolutions measurement specialties, inc., a te connectivity company. meas, measurement specialties (logo), te connectivity and te co nnectivity (logo) are trademarks. all other logos, products and/or company names referred to herein might be trademarks o f their respective owners. the information given herein, including drawings, illustrations and schematics which are intended for illustration purposes only, is believed to be reliable. however, te connectivity makes no warra nties as to its accuracy or completeness an d disclaims any liability in connection with its use. te connectivitys obligat ions shall only be as set forth in te connectivitys standard terms and conditions of sale for this product and in no case will te connectivity be liable for any incidental, indirect or consequential damages arising out of the sale, resale, use or misuse of the product. users of te connectivity products should make their own evaluation to determine t he suitability of each such product for the specific application. ? 2016 te connectivity ltd. family of companies all rights reserved. permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation fi les (the "software"), to deal in the software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of th e sof tware, and to permit persons to whom the software is furnished to do so, subject to the following conditions: the above copyright notice and this permission notice shall be included in all copies or substantial portions of the software. the software is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranti es of merchantability, f itness for a particular purpose and noninfringement. in no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of o r in connection with the software or the use or other dealings in the software.
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