digilent pmod dpot ? digital potentiometer reference manual revision: september 07 , 2012 1300 henley court | pullman, wa 99163 (509) 334 6306 voice and fax doc: 502 - 239 page 1 of 1 copyright digilent, inc. all rights reserved. other product and company names mentioned may be trademarks of their respective owners. overview the pmod dpot allows a pmod ? compatible host board to control a digital potentiometer . digilent engineers designed this pmod around t he analog devices ad 5160 digital potentiometer . functional description for a detailed description of the analog devices ad5160 please refer to the device data sheet available at analog.com . users can access t he pmoddpots programmed resistance through two methods . the p rimary means of access is via a three point screw terminal available on e v ery pmoddpot . users ma y , at their discretion, load a 3 - pi n mte cable heade r as an alternate method of access . the three terminal contacts are w ( the wiper ), a, and b. the wiper contact resistance is 60 ? . current flow between t he w iper terminal and either terminal a or b must be limited to a pulsed 20ma or a continuous 4.7ma . d o not apply voltage to any o f the terminal contacts (a, w, or b) th at exceeds the voltage rail powering the pmod . given these current flow limitations users must never apply a voltage to the terminal contacts if a host board is not powering the pmod . spi i n terface the pmoddpot communicates through a 3 - wire serial peripheral interface (spi) to configure the analog devices ad5160. note: the analog devices ad5160 is write - only . t able one de scribe s the pmod board header pin functions . these are the control signals as named on the ad5160. features include: ? 3 - wire spi? communication interface ? 10 kohm nominal resistance with minimal achievable resistance 60 ? ? 256 possible resistance settings to establish a communication interface c onnect the cs pin to the ss signal and the sdi to the sdo signal on the host board . users can c onfigure the ad5160 by sending an 8 - bit word to the device via spi. users can access maximum resistance between terminal a and w by sending 0xff . users may access t he maximum resistance between terminal b and w by sending 0x00 . table 1 interface connector signal description connector j1 C pin signal description 1 cs chip select 2 sdi serial data in 3 n/a not connected 4 sclk serial clock 5 gnd power s u pply ground 6 vcc power supply (3.3v/5v)
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