RGB LED PWM driver with nrf51

[FormerMember]

Greetings,

Here's an implementation of controlling the color of a RGB LED with a TIMER of nRF51. It works well most of the time, although it inverts polarity kind of randomly, especially when the r,g,b values are low. We know of the issue of PWM inversion with nRF51, but in this case, the timer is stopped before setting the CC values and then started again. Could any light be shed on this issue? Note: we can't use the standard PWM driver as using a timer peripheral supports only two channels, not three required for a RGB LED.

Thanks!

rgb_timer.c rgb_timer.h

[Ole Bauck]

The problem may be that you clear the timer before you stop it. If you get interrupted after clearing the timer and before stopping it, the timer counter value may go past the new CC value, and you will have inversion.

Stop before you clear instead:

rgb_timer_stop();
rgb_timer_clear();