DAC1 channel 2 and DAC2 channel 1 are not working on STM32F303

[kiiv-cz]

Only the first channel on DAC1 is working on STM32F303 (k8) as it's the only one with output buffer:

Arduino_Core_STM32/libraries/SrcWrapper/src/stm32/analog.cpp

Line 406 in 6ec82f6

dacChannelConf.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;

The other two channels are using output switch instead of output buffer enable: dacChannelConf.DAC_OutputSwitch = DAC_OUTPUTSWITCH_ENABLE;

As the HAL is using only correct struct member, it should be possible to set both without any interference:
dacChannelConf.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
dacChannelConf.DAC_OutputSwitch = DAC_OUTPUTSWITCH_ENABLE;
This solves issue that DAC1 channel 2 and DAC2 channel 1 are not getting routed out to the output pins.

However there is another issue with initialization (after the previous fix):
analogWriteResolution(12);
analogWrite(A4,512); // output is active for 5 seconds
delay(5000);
analogWrite(A3,1512); // now HAL_DAC_MspDeinit is called prior to initialize second channel and A4 is now floating
analogWrite(A5,2512); // this channel is working after the fix

Changing the order of first usage A3/A4 changes which one stops working (first one used stops working after the other channel gets "initialized" too)

[ABOSTM]

Hi @kiiv-cz, thanks for pointing out those issues and sharing your fixe.
I agree with your fixe, except that it applies only for some MCUs within STM32F3 serie. So I added a check for that.
For the 2nd point, I removed the HAL_DAC_DeInit() with was called at initialisation of DAC pin (for unknown/historical reason ??)
I submitted a PR #1326 to fix both issues.