How to add support for SAM D51/Cortex M4?

[Karl-Heinz K]

Hello,
my name is Karl-Heinz and I discovered MySensor a few days ago. I am very impressed and would like to use it for all my sensors.
I have 8bit and 32bit MCUs.
My latest MCU is an SAM D51 (Adafruit Itsybitsy M4).
I can use it when I make a minor modification to MySensors/hal/architecture/SAMD/MyHwSAMD.cpp.
When I try to compile Arduino IDE throws an error, that ADC is not defined in this context -> uint16_t hwCPUVoltage()
I have not much experience with programming. Therefore I commented all code lines in uint16_t hwCPUVoltage() and added hardcoded "return 3.3;"
Then I can compile at least what I tested so far for the SAM D51.

Of course this is not a solution. Therefore I would like to ask what is the proper way to modify MySensors for use with the Cortex M4 processors.

Thanks a lot and keep the good work going!!

Sincerely

Karl-Heinz

[mfalkvidd]

A (still incomplete but) less inelegant solution is to

return FUNCTION_NOT_SUPPORTED;

As is done for esp32 for example: https://github.com/mysensors/MySensors/blob/6ffe29cb5fcfa33fa83133044c2d16ee45c66697/hal/architecture/ESP32/MyHwESP32.cpp#L119

[Karl-Heinz K]

Hallo Mikael,
thank you for your hint.

I modified the hwCPUVoltage() part of MyHwSAMD.cpp like this. It works for me. Maybe it is not the best solution, however.

Sincerely

Karl-Heinz

uint16_t hwCPUVoltage()
{
	#ifdef __SAMD51__ 
	   return FUNCTION_NOT_SUPPORTED;
	#else

	// disable ADC
	while (ADC->STATUS.bit.SYNCBUSY);
	ADC->CTRLA.bit.ENABLE = 0x00;

	// internal 1V reference (default)
	analogReference(AR_INTERNAL1V0);
	// 12 bit resolution (default)
	analogWriteResolution(12);
	// MUXp 0x1B = SCALEDIOVCC/4 => connected to Vcc
	ADC->INPUTCTRL.bit.MUXPOS = 0x1B ;

	// enable ADC
	while (ADC->STATUS.bit.SYNCBUSY);
	ADC->CTRLA.bit.ENABLE = 0x01;
	// start conversion
	while (ADC->STATUS.bit.SYNCBUSY);
	ADC->SWTRIG.bit.START = 1;
	// clear the Data Ready flag
	ADC->INTFLAG.bit.RESRDY = 1;
	// start conversion again, since The first conversion after the reference is changed must not be used.
	while (ADC->STATUS.bit.SYNCBUSY);
	ADC->SWTRIG.bit.START = 1;

	// waiting for conversion to complete
	while (!ADC->INTFLAG.bit.RESRDY);
	const uint32_t valueRead = ADC->RESULT.reg;

	// disable ADC
	while (ADC->STATUS.bit.SYNCBUSY);
	ADC->CTRLA.bit.ENABLE = 0x00;

	return valueRead * 4;
        #endif
}