SPI more than 4 bytes generates different data

[Tostikoning]

Hi all,

when I try to send 6 bytes of 0xFF, the last bytes change. I use SPI in mode 3. I use the NRF52832 on a custom board using SDK13 with sd v4. See the following screengrab:

This is my code:

void adc_reset(void)
{
	uint32_t err_code;
	uint8_t  m_reset_buf[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};        
	while(nrf_drv_spi_transfer(&spi, m_reset_buf, 4, NULL, 0) != NRF_SUCCESS);
}

Does anyone know why this happens?

[Jørn]

Hello Tostikoning

The third arguement of the nrf_drv_spi_transfer function should be equal to the size of the transmit buffer. In your case it is set to 4, while the size of your transmit buffer is actually 6. I believe that might be the source to your problem. Try setting it to 6 or sizeof(m_reset_buf).

Best regards

Jørn Frøysa