Hi,
I tried interfacing LIS3Dh using SPI, I used the SPI example to start with, when I didn't get the desired result, I look numerous question on the forum and tried to modify the code but it does not seem to be working.
I am simply trying to read WHO_AM_I register/or any other register, I am getting FF always,
the sensor is embedded on PCB with following configurations:
Configurations:
Below code is trying to read who_am_i ( 0x0F)
#define SPI_INSTANCE 0 /**< SPI instance index. */ static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE); /**< SPI instance. */ static volatile bool spi_xfer_done; /**< Flag used to indicate that SPI instance completed the transfer. */ #define TEST_STRING "Nordic" static uint8_t m_tx_buf[]={0x0F}; /**< TX buffer. */ static uint8_t m_rx_buf[]={0x00, 0x00,0x00, 0x00,0x00}; /**< RX buffer. */ //static const uint8_t m_length = sizeof(m_rx_buf); /**< Transfer length. */ /** * @brief SPI user event handler. * @param event */ void spi_event_handler(nrf_drv_spi_evt_t const * p_event) { spi_xfer_done = true; SEGGER_RTT_printf(0,"Transfer completed.\r\n"); if (1 != 0) { SEGGER_RTT_printf(0," Received: \r\n"); NRF_LOG_HEXDUMP_INFO(m_rx_buf, strlen((const char *)m_rx_buf)); SEGGER_RTT_printf(0, "value: %u \r\n", *m_rx_buf); bsp_board_led_invert(BSP_BOARD_LED_1); } } int main(void) { bsp_board_leds_init(); APP_ERROR_CHECK(NRF_LOG_INIT(NULL)); SEGGER_RTT_printf(0,"SPI example\r\n"); 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_8M; spi_config.mode= NRF_DRV_SPI_MODE_2; APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler)); uint8_t sizerx = 2; spi_xfer_done = false; APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, 1, m_rx_buf, sizerx)); while (!spi_xfer_done){ __WFE(); } if(sizerx!=0) { SEGGER_RTT_printf(0,"Received[0]: %x %x %x %x %x \n\r",m_rx_buf[0],m_rx_buf[1],m_rx_buf[2],m_rx_buf[3],m_rx_buf[4]); }else{ SEGGER_RTT_printf(0,"no value return from \r\n"); } SEGGER_RTT_printf(0,"miso-> %u \r\n", nrf_gpio_pin_out_read(11)); SEGGER_RTT_printf(0,"mosi-> %u \r\n", nrf_gpio_pin_out_read(10)); SEGGER_RTT_printf(0,"ss-> %u \r\n", nrf_gpio_pin_out_read(12)); }
log output ( in every case I am getting FF value in rx_buff )
SDK Used: 12.2
using JLink to transfer the via SWO
I have tried with different modes and frequencies also but no luck.
Please help.
Have you checked the SPI bus with a logic analyzer, to see if anything is actually transmitted/received?
Best regards,Jørgen
No, I dont have logic analyzer
Is there any other way to check ?
You have at least two problems: you might try SPI_MODE_0 instead of MODE_2, as that works correctly with the similar part LIS2DH12. Also if this is the first time you have used SPI, it's not obvious that to receive (say) 5 bytes that you actually have to transmit 5 bytes as the transmit provides the clock required for the receive. In the case above only 1 byte is transmitted, so increase that to 5
spi_config.ss_pin = ACC_CS_PIN; spi_config.miso_pin = ACC_MISO_PIN; spi_config.mosi_pin = ACC_MOSI_PIN; spi_config.sck_pin = ACC_SCK_PIN; spi_config.frequency = NRF_SPI_FREQ_8M; spi_config.bit_order = NRF_DRV_SPI_BIT_ORDER_MSB_FIRST; spi_config.mode = NRF_DRV_SPI_MODE_0; APP_ERROR_CHECK(nrf_drv_spi_init(&mAccSpiInstance, &spi_config, acc_spi_event_handler, NULL)); static uint8_t m_tx_buf[]={0x0F, 0x00, 0x00, 0x00, 0x00}; /**< TX buffer. */ static uint8_t m_rx_buf[]={0x00, 0x00, 0x00, 0x00, 0x00}; /**< RX buffer. */ static const uint8_t m_length = sizeof(m_rx_buf); /**< Transfer length. */ // Ensure transmit and receive buffers are identical lengths #include "nrf_drv_common.h"; STATIC_ASSERT(sizeof(m_rx_buf) == sizeof(m_tx_buf));
And now specify correct lengths:
// Ensure transmit and receive buffers are identical lengths #include "nrf_drv_common.h"; // 2 bytes each or whatever .. uint8_t sizerx = 2, sizerx = 2; STATIC_ASSERT(sizetx == sizerx); APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, sizetx, m_rx_buf, sizerx));
Thanks for guiding. yeah, I am implementing SPI for first time, I increased the size of tx_buff to 5, and before sending I specify the correct length
uint8_t rx_length = 1; /**< Transfer length. */ uint8_t tx_length = 1; spi_xfer_done = false; //STATIC_ASSERT(tx_length == rx_length); APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, tx_length, m_rx_buf, rx_length)); while (!spi_xfer_done){ __WFE(); }
static uint8_t m_tx_buf[]={0x0F, 0x00, 0x00, 0x00, 0x00}; /**< TX buffer. */ static uint8_t m_rx_buf[]={0x00, 0x00, 0x00, 0x00, 0x00}; /**< RX buffer. */
I kept the mode=2 because in datasheet of sensor is says " Those lines are driven at the falling edge of SPC and should be captured at the rising edge of SPC".
Output is still FF only.
Thank you for quick reply :)
The SPI can't return the id you require using your code since the LIS doesn't know what the command is until after the 8-bit tx transfer is complete. If sending an 8-bit command that didn't require a response then a length of 1 byte transfer is fine, but you want the ID response so therefore you require a 2-byte transfer: 1st tx byte is request, 2nd a dummy 0. 1st Rx byte a dummy, 2nd a response to the Tx command request. In general the Rx stream is always 1-byte behind the tx stream since the first tx byte instructs the LIS what to put in the response.
I would stick with Mode 0 as that works .. also I would recommend finding the LIS in the examples, eg: look in Thingy SDK v2.1.0\include\frivers which can be downloaded from Nordic
/**@brief Read and verify accelerometer ID. */ static ret_code_t lis3dh_verify_id(void) { ret_code_t err_code; uint8_t reg_val; err_code = lis3dh_read_regs(WHO_AM_I, ®_val); RETURN_IF_ERROR(err_code); return (reg_val == I_AM_LIS3DH); }