SPI.begin does not set pinMode of SS as output

[marcelkottmann]

Reading the original arduino documention of SPI.begin (https://www.arduino.cc/en/Reference/SPIBegin) they say that the spi bus is configured setting the pinMode of SS to OUTPUT.
The SPI-implementation of arduino-esp32 doesn't do this.

I understand that this is totally unnecessary in Master-mode, but it introduces a major incompatibility to libs that are relying on that and where the SS pin is not explicitly set as output by the lib.

arduino-esp32/libraries/SPI/src/SPI.cpp

Lines 37 to 68 in e5ea089

	void SPIClass::begin(int8_t sck, int8_t miso, int8_t mosi, int8_t ss)
	{
	if(_spi) {
	return;
	}
	if(!_div) {
	_div = spiFrequencyToClockDiv(_freq);
	}
	_spi = spiStartBus(_spi_num, _div, SPI_MODE0, SPI_MSBFIRST);
	if(!_spi) {
	return;
	}
	if(sck == -1 && miso == -1 && mosi == -1 && ss == -1) {
	_sck = (_spi_num == VSPI) ? SCK : 14;
	_miso = (_spi_num == VSPI) ? MISO : 12;
	_mosi = (_spi_num == VSPI) ? MOSI : 13;
	_ss = (_spi_num == VSPI) ? SS : 15;
	} else {
	_sck = sck;
	_miso = miso;
	_mosi = mosi;
	_ss = ss;
	}
	spiAttachSCK(_spi, _sck);
	spiAttachMISO(_spi, _miso);
	spiAttachMOSI(_spi, _mosi);
	}

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[marcelkottmann]

Seems like noone has an opinion about that :-)

[atanisoft]

@PePe79 submit a PR that implements this and it can be evaluated for inclusion.

[marcelkottmann]

I am really unsure, if I had a misconception or if this is really a bug and noone has stumbled upon this problem. So my intention was to get some more opinions. In the meantime I also found another code line in https://github.com/espressif/arduino-esp32/blob/master/libraries/SPI/examples/SPI_Multiple_Buses/SPI_Multiple_Buses.ino
where the problem is solved manually by setting SS in OUTPUT mode, but missing setting it to a HIGH value:

//set up slave select pins as outputs as the Arduino API
//doesn't handle automatically pulling SS low
pinMode(5, OUTPUT); //VSPI SS
pinMode(15, OUTPUT); //HSPI SS

I think that SPI.begin should set SS as OUTPUT and set SS to HIGH, as stated in https://www.arduino.cc/en/Reference/SPIBegin
If I get some positive response, I would be happy to create a PR for that.

[atanisoft]

@PePe79 I agree from the description of that Arduino spec it does seem that the SS HIGH step is missing.

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[STALE_SET] This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

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