Hello,
I have found similar questions on transmitting multiple bytes over SPI, but I am still not sure how to do it. I want to communicate with a driver which needs to be configured by writing 20 bits at a time to the chip. One write value could fx. be 0xD0505 (20 bits containing both the register address and the data).
I am trying to modify the nRF5 SDK (v12.2.0) SPI master example. My modifications are shown below.
So I have chosen a tx buffer size of 3 bytes (closest to 20 bit value) and then when transmitting the 20 bit value I simply use m_tx_buf[0] = 0xD0505.
I am very unsure about the [0] index in 'm_tx_buf[0]'. Is that going to work or will it only take the first 8 bits of the 20 bit value?
And also setting the 3 byte buffer size when I don't have an exact 3 byte value to transmit. Do I need to shift the data to get the correct value?
Any help is appreciated. Thanks.
regards,
Jan
******* Code snippet ********
static uint8_t m_tx_buf[3]; // I need to transmit 20 bits at once, so 3 bytes is required
static uint8_t m_rx_buf[3]; /**< RX buffer. */
static const uint8_t m_length = sizeof(m_tx_buf); /**< Transfer length. */
while (1)
{
// Reset rx buffer and transfer done flag
memset(m_rx_buf, 0, m_length);
spi_xfer_done = false;
m_tx_buf[0] = 0xD0505; // 20 bit value to be transmitted
APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, m_length, m_rx_buf, m_length));
while (!spi_xfer_done)
{
__WFE(); // Wait For Event
}
NRF_LOG_FLUSH();
bsp_board_led_invert(BSP_BOARD_LED_0);
nrf_delay_ms(5000);
}
