Autocalobrate issues with MPR121- dead inputs occaisonally after startup

[johncohn]

Folks,

   I'm using MPR121's for a large musical instrument. the whole instrument is made up of 6 different keyboard structures each with an MPR121 and an Arduino Mega.. all in all it works quite well. The issue I'm having is with the autocalibration   routines. At startup, I use the MPR121 autocalibrate to automatically set the operating point for each of the 'keys' . Generally it works great. and all  6 keyboards come up wiht all 11 keys on each working. .  Occasionally, however  one or two of the units will come  with 1-3 keys that are not working.. I can always clear the condition by doing a full power on reset a time or two, but that's inconvenience. Any idea why I'm getting this flaky behavior ? Could I have the thresholds set wrong or something ?   Thanks for any quick help.. This thing goes on the road in 2 weeks !

-jc

I've attached a copy of the MPR121 register settings I'm using..

Original Attachment has been moved to: BIG_mpr121_settings.txt.zip

[reyes]

Hi,

I think that it’s possible that the problem its timing related (it’s possible that you are not running at the 400 kHz needed for the MPR121).

But you can find a code example for the MPR121 using the ATmega328 on the link below, I would recommend you to test your MPR121 using the code on this link:

https://www.sparkfun.com/products/9695

Or you can test it using our suggested initialization code:

#define TouchThre 10   //15//30//10

#define ReleaThre 6   //8//25//8

void MPR121_init(void)

{

  //Reset MPR121 if not reset correctly

  IIC_ByteWrite(0x80,0x63);  //Soft reset

  IIC_ByteWrite(0x5E,0x00);  //Stop mode 

  //touch pad baseline filter

//rising                                   

  IIC_ByteWrite(0x2B,0x01); // MAX HALF DELTA Rising

  IIC_ByteWrite(0x2C,0x01); // NOISE HALF DELTA Rising

  IIC_ByteWrite(0x2D,0x0E); // NOISE COUNT LIMIT Rising

  IIC_ByteWrite(0x2E,0x00); // DELAY LIMIT Rising

  //falling

  IIC_ByteWrite(0x2F,0x01); // MAX HALF DELTA Falling

  IIC_ByteWrite(0x30,0x05); // NOISE HALF DELTA Falling

  IIC_ByteWrite(0x31,0x01); // NOISE COUNT LIMIT Falling

  IIC_ByteWrite(0x32,0x00); // DELAY LIMIT Falling

  //touched

  IIC_ByteWrite(0x33,0x00); // Noise half delta touched

  IIC_ByteWrite(0x34,0x00); // Noise counts touched

  IIC_ByteWrite(0x35,0x00); // Filter delay touched

  //Touch pad threshold

  IIC_ByteWrite(0x41,TouchThre); // ELE0 TOUCH THRESHOLD

  IIC_ByteWrite(0x42,ReleaThre); // ELE0 RELEASE THRESHOLD

  IIC_ByteWrite(0x43,TouchThre); // ELE1 TOUCH THRESHOLD

  IIC_ByteWrite(0x44,ReleaThre); // ELE1 RELEASE THRESHOLD

  IIC_ByteWrite(0x45,TouchThre); // ELE2 TOUCH THRESHOLD

  IIC_ByteWrite(0x46,ReleaThre); // ELE2 RELEASE THRESHOLD

  IIC_ByteWrite(0x47,TouchThre); // ELE3 TOUCH THRESHOLD

  IIC_ByteWrite(0x48,ReleaThre); // ELE3 RELEASE THRESHOLD

  IIC_ByteWrite(0x49,TouchThre); // ELE4 TOUCH THRESHOLD

  IIC_ByteWrite(0x4A,ReleaThre); // ELE4 RELEASE THRESHOLD

  IIC_ByteWrite(0x4B,TouchThre); // ELE5 TOUCH THRESHOLD

  IIC_ByteWrite(0x4C,ReleaThre); // ELE5 RELEASE THRESHOLD

  IIC_ByteWrite(0x4D,TouchThre); // ELE6 TOUCH THRESHOLD

  IIC_ByteWrite(0x4E,ReleaThre); // ELE6 RELEASE THRESHOLD

  IIC_ByteWrite(0x4F,TouchThre); // ELE7 TOUCH THRESHOLD

  IIC_ByteWrite(0x50,ReleaThre); // ELE7 RELEASE THRESHOLD

  IIC_ByteWrite(0x51,TouchThre); // ELE8 TOUCH THRESHOLD

  IIC_ByteWrite(0x52,ReleaThre); // ELE8 RELEASE THRESHOLD

  IIC_ByteWrite(0x53,TouchThre); // ELE9 TOUCH THRESHOLD

  IIC_ByteWrite(0x54,ReleaThre); // ELE9 RELEASE THRESHOLD

  IIC_ByteWrite(0x55,TouchThre); // ELE10 TOUCH THRESHOLD

  IIC_ByteWrite(0x56,ReleaThre); // ELE10 RELEASE THRESHOLD

  IIC_ByteWrite(0x57,TouchThre); // ELE11 TOUCH THRESHOLD

  IIC_ByteWrite(0x58,ReleaThre); // ELE11 RELEASE THRESHOLD

  //touch /release debounce

  IIC_ByteWrite(0x5B,0x00);

  // response time = SFI(10) X ESI(8ms) = 80ms

  IIC_ByteWrite(0x5D,0x13);   

  //FFI=18

  IIC_ByteWrite(0x5C,0x80); 

  //Auto configuration

  IIC_ByteWrite(0x7B,0x8F);

  // charge to 70% of Vdd , high sensitivity

  IIC_ByteWrite(0x7D,0xE4);

  IIC_ByteWrite(0x7E,0x94);

  IIC_ByteWrite(0x7F,0xCD);

  // 12 electrodes enabled   

  IIC_ByteWrite(0x5E,0xCC); 

}

Regards,

Jose