Using PWM on GPIO on MPR121

[paulwilson]

Hello,

I am using an MPR121 with 5 touch pads and 5 LED outputs. The LED outputs are on lines LED1, LED2, LED3, LED3, LED5. I can turn all 5 LEDs on and off with the set and clear registers. However, when I attempt to use PWM on the LED outputs, LEDs 1 through 4 operate as expected but LED5 does not. Specifically, if the PWN is turned off (corresponding PWN nibble = 0), I can turn LED5 on and off but if I set the corresponding PWN nibble to any value other than 0, the LED is not illuminated. I have confirmed that there is no signal at all on LED under that condition by means of an oscilloscope. Does anyone else have any experience using the GPIO outputs on the MPR121 with PWM? If so, any ideas as to why I cannot get it to work for LED5.

[TomasVaverka]

Hello Paul,

The PWM5 bit control has logic bug. Currently there is a workaround to set LED5 and LED6 with the same DAT setting (DAT[5] = DAT[6] = 1) or reconnect to ELE11/LED7 if possible.

Sorry about this. Both the datasheet and AN3894 needs to be updated to reflect this problem.

Regards,

Tomas

[paulwilson · Accepted solution]

Thanks Tomas, the timing works out well as we have a meeting this

morning to discuss transitioning the hardware from a prototype to the

final design.

Best Regards,

Paul

[djmitch]

Hello Paul,

I use the mpr121 on my raspberry.

The touch sensors works well.

But how can i use the inputs

To connect a led.

I found no codes anywhere.

I use python.

Can you help me ?

Thank you.