STM32 SPI Cant Set SSM Bit

[Defensive]

Hi, Im new to STM32 and Im writing a bare metal spi library however for some reason when I try to change the SSM bit in code it doesnt seem to work. Im able to change the SSM bit in debug mode.

void SPI_Enable(SPI_Com* spi)
{
	SPI1_CLK_EN;


	//Reset the whole CR1 register if someone decides to enable it using different options
	//First disable SPI
	spi->spiReg->SPI_CR1 &= ~(1 << 6);
	spi->spiReg->SPI_CR1 = 0;

	//CPOL and CPHA
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.CPHA);
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.CPOL << 1);


	//Master, Slave mode
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.masterMode << 2);

	//Set baud rate
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.baudRate << 3);

	//MSB or LSB first
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.isLSB << 7);

	//Data format
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.dataFormat << 11);

	//Software Slave SSM and SSI bits
	//spi->spiReg->SPI_CR1 |= (spi->spiConfig.isSoftwareSlave << 9);
	spi->spiReg->SPI_CR1 |= (1 << 9);
	spi->spiReg->SPI_CR1 |= (1 << 8);


	//Set duplex modes
	switch(spi->spiConfig.duplexMode)
	{
	case FULL_DUPLEX_MODE:
		//You dont have to change since by default its in full duplex mode
		break;

	case HALF_DUPLEX_MODE:
		spi->spiReg->SPI_CR1 |= (1 << 15);
		break;

	case RECIEVE_ONLY_MODE:
		spi->spiReg->SPI_CR1 |= (1 << 10);
		break;
	}

	//Bidi mode
	spi->spiReg->SPI_CR1 |= (spi->spiConfig.bidiMode << 14);

	//Set CS to high
	SetOutputAdress(spi->CS, 1);

	//Set busy to 0
	spi->isBusy = 0;

	spi->spiReg->SPI_CR1 |= (1 << 6);

}

[Pavel A.]

Some mode bits can be changed only when the SPI is disabled or transfer not active etc. See the RM.

[waclawek.jan]

> when I try to change the SSM bit in code it doesnt seem to work

What are exactly the symptoms, how do you check that?

Which STM32 in particular? What are its clock settings?

I would recommend to "assemble" all these bits into one local variable, and then write that variable into SPI_CR1 register in one single straight write, rather than have a sequence of read-modify-writes.

JW

[Defensive · Accepted solution]

Hi, after testing some stuff it appears there was a problem within the inbuilt debugger causing it to skip some lines of code or something like that. I dont know what seemed to cause it. It seems to be fixed now but when i tried to unplug/restart the cube ide at that time it wasnt working. Sorry to bother