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System: MPR121 controlled by FRDM KL25

Question asked by Menahem Yudkovich on Jan 29, 2015
Latest reply on Feb 10, 2015 by Jose Alberto Reyes Morales




Development environment : IAR ver.6.6


System: MPR121 controlled by FRDM KL25


  • Problem description: can't update electrode configuration register(0x5E) while MPR121 in run mode.


The MPR121 is set to work in auto configuration mode (reg.0x7B=0x0B),all electrode include proximity are enabled(reg.0x5E=0x3C).


After the first interrupt caused by the proximity electrode I'm waiting for the release interrupt then I try to write a new setting to the register


0x5E=0x0C(12 ele. enable, prox ele. disable) while in run mode. After the writing I read the value of reg.0x5E  it still equals to 0x3C .


After the first proximity detection I want to disable the proximity and work just with the 12 key pad electrodes,


According to the manual the only register that is writable during run mode is 0x5E  what could be the problem?


The attached screen shots are the reading of all MPR121 registers values after initialization.


  • One more thing I use the KITMPR121EVM 12 electrode numeric keypad with the current setting (see attached files)

    a proximity detection is made approximately 2-3 cm from the keypad surface, what is the max. distance that can be reached with that keypad?