ESP32 - SPI - Accelerometer

Projects Programming
1

I wrote a code to interface ADXL355 to ESP32 using SPI. Previously, I set up the sensor using ARM STM32 H7 and it worked properly. now it seems that the SPI doesn't work because I can not read the values are sent by Sensor. Any Idea where is the problem?

Thanks for your response in advance.

Here is the code I wrote:

#include <SPI.h>
#include <Arduino.h>


#define HSPI_MISO   12
#define HSPI_MOSI   13
#define HSPI_SCLK   14
#define HSPI_SS     15

//function prototypes;
uint8_t hspiSend_ReceiveByte(byte stuff);

//uninitalised pointers to SPI objects
SPIClass * hspi = NULL;
static const int spiClk = 1000000; // 1 MHz

//Address for the Range Register
const uint8_t RANGE = 0x2C;    //Considered Reset value for this Register is 0x81.
const uint8_t RANGE_2G = 0x01;  //value to set the 2G_range of the sensor
const uint8_t POWER_CTL = 0x2D; //Power control Register's Address.
const uint8_t MEASURE_MODE = 0x06; // Only accelerometer
const uint8_t ADXL_Reset_Reg_Address= 0x2F;  //this Reg is only Writable. put 0x00 to this Reg onorder to reset it.
                                             //Senors's reset register address

uint8_t  READ_BYTE = 0x01;
uint8_t WRITE_BYTE = 0x00;
uint8_t reg_adress = 0x00;

//address of the X axis
const uint8_t XDATA3 = 0x08;
const uint8_t XDATA2 = 0x09;
const uint8_t XDATA1 = 0x0A;

//X axis variables
int8_t xdata[3]={0,0,0};
int32_t Xdata_i=0;
float Xdata_d=0;

char uart_buff[50];

void setup() {
  //initialise two instances of the SPIClass attached to VSPI and HSPI respectively
  hspi = new SPIClass(HSPI);
  

//#ifndef ALTERNATE_PINS
  //initialise hspi with default pins
  //SCLK = 14, MISO = 12, MOSI = 13, SS = 15
  //hspi->begin();
//#else
  //alternatively route through GPIO pins
  hspi->begin(HSPI_SCLK, HSPI_MISO, HSPI_MOSI, HSPI_SS); //SCLK, MISO, MOSI, SS
//#endif

  //set up slave select pins as outputs as the Arduino API
  pinMode(HSPI_SS, OUTPUT); //HSPI SS

  //resetting the ADXL
  reg_adress = (ADXL_Reset_Reg_Address << 1) | WRITE_BYTE; //reset reg address : 0x2F, value : 0x52
  hspiSend_ReceiveByte(reg_adress);
  hspiSend_ReceiveByte(0x52);

  //Setting the ADXL Range to 2G
  reg_adress = (RANGE << 1) | WRITE_BYTE;
  hspiSend_ReceiveByte(reg_adress);
  hspiSend_ReceiveByte(RANGE_2G);
  
  //Setting the ADXL to the measurment mode.
  reg_adress = (POWER_CTL << 1) | WRITE_BYTE;
  hspiSend_ReceiveByte(reg_adress);
  hspiSend_ReceiveByte(MEASURE_MODE);

  Serial.begin(921600);
}

// the loop function runs over and over again until power down or reset
void loop() {
  //use the SPI buses
  //vspiCommand();
  reg_adress = (XDATA1 << 1) | READ_BYTE;
  xdata[0] = hspiSend_ReceiveByte(reg_adress);

  reg_adress = (XDATA2 << 1) | READ_BYTE;
  xdata[1] = hspiSend_ReceiveByte(reg_adress);

  reg_adress = (XDATA3 << 1) | READ_BYTE;
  xdata[2] = hspiSend_ReceiveByte(reg_adress);
  
  Xdata_i = ((int32_t)xdata[0] >> 4) + ((int32_t)xdata[1] << 4) + ((int32_t)xdata[2] << 12);
  Xdata_d = (float)Xdata_i/256000;

  sprintf(uart_buff , "Sensor data: %f", Xdata_d);
  Serial.println(uart_buff);
  
  //sprintf(uart_buff , "Sensor data: %d", xdata[2]);
  //Serial.println(uart_buff);
  delay(2000);
}


uint8_t hspiSend_ReceiveByte(byte stuff) {
  
  uint8_t retnd_result;
  hspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
  digitalWrite(HSPI_SS, LOW);
  retnd_result = hspi->transfer(stuff);
  digitalWrite(HSPI_SS, HIGH);
  hspi->endTransaction();
  return retnd_result;

}
2

Try using a low-cost logic analyzer such as this to see what's happening on the bus.

Also, why are you instantiating a new SPIClass object? Why not just use the one that's defined by the Arduino ESP32 core (i.e. 'SPI')?

3

Thanks for your response. as you suggested, I avoided using the SPI class and used only the the SPI.transfer(...); function and the problem is solved.

4

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