An alternative way of dealing with PWM pins

[MCUdude]

This is something that has bugged me for quite a while with MegaCoreX. PWM pin routing is somewhat flexible on these modern AVRs, but I've been forced to place them in fixed positions that overlap the least with other peripherals. I think it's a shame that the possibility of re-routing the PWM output is thrown out the window. It is possible to reconfigure the PORTMUX and the various timers yourself, but it takes a lot of time and effort to dive into the datasheet to figure everything out when you just want a simple PWM signal on a different pin.

My idea is to supplement the Arduino framework with a few additional functions that will make routing and minor reconfiguring much easier. I'm not talking about full-blown TCA and TCB reconfiguring, just the possibility to re-route, change the resolution, and clock prescaler.

I've come up with the following functions and enums to pass along:

void pwmWrite(pwm_timers_t pwmTimer, uint16_t value, timers_route_t timerRoute = ROUTE_UNTOUCHED);
void pwmPrescaler(pwm_timers_t pwmTimer, timers_prescaler_t prescaler);
void pwmSetResolution(pwm_timers_t pwmTimer, uint8_t maxValue);

// Located in pins_arduino.h
enum pwm_timers_t : uint8_t {
  TCA0_0 = 0,
  TCA0_1 = 1,
  TCA0_2 = 2,
  TCA0_3 = 3,
  TCA0_4 = 4,
  TCA0_5 = 5,
  TCB_0  = 6,
  TCB_1  = 7,
  TCB_2  = 8,
  TCB_3  = 9,
};

// Located in pins_arduino.h
enum timers_route_t : uint8_t {
  ROUTE_TCA0_PORTA = 0x40,
  ROUTE_TCA0_PORTB = 0x41,
  ROUTE_TCA0_PORTC = 0x42,
  ROUTE_TCA0_PORTD = 0x43,
  ROUTE_TCA0_PORTE = 0x44,
  ROUTE_TCA0_PORTF = 0x45,
  ROUTE_TCB0_PA2   = 0x00,
  ROUTE_TCB0_PF4   = 0x01,
  ROUTE_TCB1_PA3   = 0x10,
  ROUTE_TCB1_PF5   = 0x11,
  ROUTE_TCB2_PC0   = 0x20,
  ROUTE_TCB2_PB4   = 0x21,
  ROUTE_TCB3_PB5   = 0x30,
  ROUTE_TCB3_PC1   = 0x31,
  ROUTE_UNTOUCHED  = 0x80,
};

// Located in Arduino.h
enum timers_prescaler_t : uint8_t {
  TCA_DIV1    = 0x00,
  TCA_DIV2    = 0x02,
  TCA_DIV4    = 0x04,
  TCA_DIV8    = 0x06,
  TCA_DIV16   = 0x08,
  TCA_DIV64   = 0x0A,
  TCA_DIV256  = 0x0C,
  TCA_DIV1024 = 0x0E,
  TCB_DIV1    = 0x00,
  TCB_DIV2    = 0x20,
  TCB_CLKTCA  = 0x40,
};

The development branch for this is located here. Again, the goal is not to expose every timer function imaginable; it's just a set of functions to make it easier to reconfigure the 8-bit PWM outputs. The reason why I'm using enums is to force the user to actually use this and hopefully throw an error if a non-compatible constant is used.

Let's say you want PWM output on pin PB2 using timer TCA0 and a custom prescaler. Easy!

uint8_t duty = 0x80;
pwmPrescaler(TCA0_2, TCA_DIV8);
pwmWrite(TCA0_2, duty, ROUTE_TCA0_PORTF);

@SpenceKonde I'd like to hear your thoughts on this. Have you been in a situation where you'd like to re-map PWM pins?

[MCUdude]

I've updated the extended API documentation where the new PWM related functions have been added:
https://github.com/MCUdude/MegaCoreX/blob/pwm_write/Extended-API.md