Want to send value on a particular register using SPI

RE: Want to send value on a particular register using SPI

Meera Shah — Fri, 25 Jan 2019 06:53:30 GMT

Yes .......I found the solution of my problem. I was masking MSB bit of a register for both read and write operation, but it is needed for read operation only.

void spi_read(uint8_t register_pointer)
{
    ret_code_t err_code;
    uint8_t tx_data;
   
    memset(spi_rx_data,0x00,sizeof(spi_rx_data));
    register_pointer |= 0x80;   //this is needed for reading operation
    tx_data = register_pointer;
   
    err_code = nrf_drv_spi_transfer(&spi, &tx_data,1, spi_rx_data,sizeof(spi_rx_data));
    NRF_LOG_HEXDUMP_INFO(spi_rx_data,sizeof(spi_rx_data));
    APP_ERROR_CHECK(err_code);  
   
}

void spi_write(uint8_t register_pointer, uint8_t register_value)
{
    ret_code_t err_code;
    memset(spi_rx_data,0x00,sizeof(spi_rx_data));
    
    data[0] = register_pointer;    //no need of masking higher bit of register
    data[1] = register_value;
    
    err_code = nrf_drv_spi_transfer(&spi, data,sizeof(data), spi_rx_data,sizeof(spi_rx_data));
    NRF_LOG_HEXDUMP_INFO(spi_rx_data,sizeof(spi_rx_data));
    APP_ERROR_CHECK(err_code);  
}

RE: Want to send value on a particular register using SPI

Jørgen Holmefjord — Wed, 23 Jan 2019 12:05:45 GMT

Are you sure that the write operation will echo back the value written to the register? What happens if you read/write it once again? Can you post your entire code you used for writing/reading the registers?

RE: Want to send value on a particular register using SPI

Meera Shah — Wed, 23 Jan 2019 10:12:35 GMT

I am working with LIS2DH12 connected with nrf51822 taiyo udan board. I did whatever you say but still I am getting output spi_read_write(ACCEL_REG_CTRL0,0x00) (before) : FF 10

after spi_read_write(ACCEL_REG_CTRL0,0x90) : FF 10

RE: Want to send value on a particular register using SPI

Jørgen Holmefjord — Wed, 23 Jan 2019 10:01:52 GMT

Sorry, I missed that part of your comment. What device you are interfacing? Note that the RX buffer will be filled while transferring the TX bytes to the device. If you expect to receive data after TX is completed, you will have to set the RX buffer length to size of TX + RX buffer and discard the first bytes.

RE: Want to send value on a particular register using SPI

Meera Shah — Wed, 23 Jan 2019 09:25:19 GMT

But I am using blocking mode(so no interrupt). spi_rx_data should come up with the updated register value. Please help me with this.

RE: Want to send value on a particular register using SPI

Jørgen Holmefjord — Wed, 23 Jan 2019 09:22:09 GMT

Delays does not guarantee that the transfer is completed. You should wait for the done event in the event handler.

RE: Want to send value on a particular register using SPI

Meera Shah — Wed, 23 Jan 2019 04:51:29 GMT

i added nrf_delay_ms(200); between spi_read_write_reg() and spi_read_write() but no change... Also I am working with

blocking mode of SPI.

#define SPI_SS_PIN   4
#define SPI_MOSI_PIN 21
#define SPI_MISO_PIN 22
#define SPI_SCK_PIN 24


void spi1_init(void)
{
    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin   = SPI_SS_PIN;
    spi_config.miso_pin = SPI_MISO_PIN;
    spi_config.mosi_pin = SPI_MOSI_PIN;
    spi_config.sck_pin  = SPI_SCK_PIN;
    spi_config.frequency= NRF_DRV_SPI_FREQ_4M;
    spi_config.mode= NRF_DRV_SPI_MODE_0;
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, NULL));

}

RE: Want to send value on a particular register using SPI

Jørgen Holmefjord — Tue, 22 Jan 2019 15:13:52 GMT

Hi,

If you have initialized the SPI driver in non-blocking mode (by providing an event handler to nrf_drv_spi_init), you will have to wait for one transfer to complete before starting a new one (by calling spi_read_write_reg()/spi_read_write()). Please reference the SPI master example in the SDK on how to do this.

Best regards,
Jørgen