spi fails after removing print statements

[faikab]

So i am utilizing SPI and i got it to work, however for some absurd reason after removing the segger_print statement below from before the while loop the spi would stop functioning. otherwise it works perfectly fine. Any idea why a print statement would cause this? do i need to add a delay? Although i would expect the while loop to handle any delay necessary.

uint32_t LCD_SPI_Write_Command (uint8_t command)
{
	spi_lcd_xfer_done = false;
	LCD_CSX_LOW(); //	set CSX to low to activate LCD listening
	LCD_DCX_LOW(); // indicate command
	uint32_t err_code = nrf_drv_spi_transfer(&m_spi_LCD, &command, 1, NULL, 0);
	if (err_code != NRF_SUCCESS) {
		SEGGER_RTT_printf(0, "[ERROR] on command transfer :%d \n", err_code);
	}
		SEGGER_RTT_printf(0,"Im writing a command! \n");

	while (!spi_lcd_xfer_done)
	  {
	  }
	return err_code;
}

[kl-cruz]

It is not needed to load it everytime from RAM memory. In the end variable will be updated, but without volatile keyword You worked on local copy. RTT functions adding and removing - Compiler probably was lack of available registers and do writing/reading operations. That's why it worked. So You are lucky one.

[kl-cruz]

Yes, You can do something like this like You describe. It is better to do things asynchronously than synchronously. Of course if You want to save some energy. You can also try to fill buffers in main function, start first transmission, then fill next buffers and then only update pointer in irq handler/callback to next buffers and start next transmission (in irq context). You can do two things in one time (load new data to buffers and send another data). Just doublebuffered!