Driving ADXL345 via SPI

Khansokhua · ‎2025-02-26

Board: STM32F407G-DISC1

IDE : StmCubeIDE

Hello,

I am trying to drive ADXL345 accelerometer sensor via SPI. I succeed in receiving the device address (0xE5).

However, afterwards, when I tried to read two registers' value consecutively. I always read the first read's value, so they are both the same value. I have not figured it out yet. I set SSOE bit and HW NSS is also set. Could anyone explain where I missed? Thanks in advance.

Have a nice day


void spixInit(const SPI_Handle_t* handler)
{
	SPI_RegDef_t* spi = handler->spiSelect;

	if(spi == SPI1)
		SPI1_CLOCK_ENABLE();
	else if(spi == SPI2)
		SPI2_CLOCK_ENABLE();
	else if(spi == SPI3)
		SPI3_CLOCK_ENABLE();

	spi->SPI_CR1 = 0;
	spi->SPI_CR1 |= ( handler->pinConfig.cphase << 0);
	spi->SPI_CR1 |= ( handler->pinConfig.cpol << 1);
	spi->SPI_CR1 |= ( handler->pinConfig.mode << 2);
	spi->SPI_CR1 |= ( handler->pinConfig.baudRate << 3);
	spi->SPI_CR1 |= ( handler->pinConfig.firstBit << 7);
	spi->SPI_CR1 |= ( handler->pinConfig.dataSize << 11);
	/*
	 * Default full-duplex two wire
	 * Default NSS  in HW mode, since we will use single slave mostly
	 */
	if(!(spi->SPI_CR1 & (1u << 9))) // if HW NSS enabled
		spi->SPI_CR2 |= (1u << 2);	// set slave select	 automatically

	spi->SPI_CR1 |= ( 1u << 13); // CRC enable
	spi->SPI_CR1 |= ( 1u << 6); // peripheral enable
}
void spixSendDataByte(SPI_RegDef_t* spi, const uint8_t* buffer, size_t size)
{

	while(size--)
	{
		while(!(spi->SPI_SR & (1u << 1)))
		; // wait until TX buffer empty
		spi->SPI_DR = *buffer++;
	}

	while(spi->SPI_SR & (1u << 7))
			;  // wait until busy flag reset

}
void spixReceiveDataByte(SPI_RegDef_t* spi, uint8_t* buffer, size_t size)
{

	while(size--)
	{
		while(!(spi->SPI_SR & (1u << 0)))
		; // wait until RX buffer is not empty
		*buffer++ = spi->SPI_DR;
	}

	while(spi->SPI_SR & (1u << 7))
			;  // wait until busy flag reset
}
uint8_t readRegisterDataAdxl345(uint8_t registerAddress ) //
{
		uint8_t readBuffer = 0;

		registerAddress |= 0x80; // set for read operation
		//gpioWritePin(GPIOA, GPIO_PIN_4, 0);
		spixSendDataByte(SPI1, &registerAddress , 1);

		spixReceiveDataByte(SPI1, &readBuffer, 1);
		//gpioWritePin(GPIOA, GPIO_PIN_4, 1);

		return readBuffer;
}
int main(void)
{

	/*
	 * PA4 - PA5 - PA6 - PA7 pins must be configured in AF mode for SPI1
	 */

	GPIO_Handle_t SP1_NSS_PA4 = {	 // on ADXL345 connected to CS pin
									.PORTNAME = GPIOA,
									.PINCONF.PIN = GPIO_PIN_4,
									.PINCONF.MODE = GPIO_MODE_ALTARNATE,
									.PINCONF.OTYPE = GPIO_OTYPE_PP,
									.PINCONF.OSPEED = GPIO_OSPEED_HIGH,
									.PINCONF.PUPD = GPIO_PUPD_NO,
									.PINCONF.AF = AF5
								};
	GPIO_Handle_t SP1_SCK_PA5 = { 	 // on ADXL345 connected to SCL pin
									.PORTNAME = GPIOA,
									.PINCONF.PIN = GPIO_PIN_5,
									.PINCONF.MODE = GPIO_MODE_ALTARNATE,
									.PINCONF.OTYPE = GPIO_OTYPE_PP,
									.PINCONF.OSPEED = GPIO_OSPEED_HIGH,
									.PINCONF.PUPD = GPIO_PUPD_NO,
									.PINCONF.AF = AF5
								};
	GPIO_Handle_t SP1_MISO_PA6 = {   // on ADXL345 connected to SDO pin
									.PORTNAME = GPIOA,
									.PINCONF.PIN = GPIO_PIN_6,
									.PINCONF.MODE = GPIO_MODE_ALTARNATE,
									.PINCONF.OTYPE = GPIO_OTYPE_PP,
									.PINCONF.OSPEED = GPIO_OSPEED_HIGH,
									.PINCONF.PUPD = GPIO_PUPD_PU,
									.PINCONF.AF = AF5
								};
	GPIO_Handle_t SP1_MOSI_PA7 = {   // on ADXL345 connected to SDA pin
									.PORTNAME = GPIOA,
									.PINCONF.PIN = GPIO_PIN_7,
									.PINCONF.MODE = GPIO_MODE_ALTARNATE,
									.PINCONF.OTYPE = GPIO_OTYPE_PP,
									.PINCONF.OSPEED = GPIO_OSPEED_HIGH,
									.PINCONF.PUPD = GPIO_PUPD_NO,
									.PINCONF.AF = AF5
								};

	gpioInit(&SP1_NSS_PA4);
	gpioInit(&SP1_SCK_PA5);
	gpioInit(&SP1_MISO_PA6);
	gpioInit(&SP1_MOSI_PA7);


	/*
	 *  SPI configuration must be made according to the ADXL345 requirements
	 */

	SPI_Handle_t SPI1_ADXL345 = {   .spiSelect = SPI1,
									.pinConfig.mode = SPI_DEVICE_MASTER,
									.pinConfig.baudRate = SPI_BAUD_RATE_PRESC_16, // 1 MHz clock, since main clock 16 Mhz HSI
									.pinConfig.cpol = SPI_CPOL_IDLE_1,
									.pinConfig.cphase = SPI_CPHASE_SECOND_EDGE,
									.pinConfig.dataSize = SPI_DATA_SIZE_8,
									.pinConfig.firstBit = SPI_MSB_FIRST,
 
								};

	spixInit(&SPI1_ADXL345);

    uint8_t deviceAddressADXL345 = readRegisterDataAdxl345(DEVID_BASE_ADDR); // 0xE5           
    uint8_t bwRateVal = readRegisterDataAdxl345(BW_RATE_BASE_ADDR); // 0xE5

	while(1)
        {
        }
}

tjaekel · ‎2025-03-01

ADXL345 datasheet says:
"To read or write multiple bytes in a single transmission, the multiple-byte bit, located after the R/ W bit in the first byte transfer analog.com (MB in Figure 37 to Figure 39), must be set."

Have you done?