Problem reading L3GD20H gyroscope in SPI

Other Hardware General Electronics
1

Hello!

This is my first time posting so I'm not sure how this works, but I've been working on reading the registers for the L3GD20H gyroscope in SPI. I need to make sure my readRegister function is working in order to read the registers of my gyroscope. So, the issue is that the readRegister function is returning 5 bits instead of 8. When I go to read the WHOAMI register it returns 11010 and instead should return 1101 0111 as per page 36 of the datasheet
l3gd20h.pdf (2.4 MB)
Here's my code,

#include <SPI.h>

const int WHOAMI = 0xD7;
const int CTRL1 = 0x20;
const int OUT_X_L = 0x28;
const int OUT_X_H = 0x29;
const int OUT_Y_L = 0x2A;
const int OUT_Y_H = 0x2B;
const int OUT_Z_L = 0x2C;
const int OUT_Z_H = 0x2D;
const int STATUS = 0x27;
const int LOW_ODR = 0x39;

// readData = 0x80;  
// writeData = 0x00;
long gx[16], gy[16], gz[16];      // 16 bit

unsigned long timeLimit = 60000; // 60s

const int GYRO_CS = 10; // labeled CS
const int GYRO_MISO = 12; // labeled SA0  
const int GYRO_MOSI = 11;  // labeled SDA 
const int GYRO_CLK = 13; // labeled SCL


void setup() {
  Serial.begin(9600); // setting the baud rate
  SPI.begin();
  
  pinMode(GYRO_CS, OUTPUT);
  digitalWrite(GYRO_CS, HIGH);

  Serial.println(readRegister(WHOAMI)); // prints 11010, should return 1101 0111
  // writeRegister(CTRL1, 0x0F); // enables normal mode and x,y,z axis


}


void loop() {
}


  
byte readRegister(byte address) {
  byte inByte = 0;
  SPI.beginTransaction(SPISettings(10000000, MSBFIRST, SPI_MODE0));
  digitalWrite(GYRO_CS, LOW); 
  SPI.transfer(address | 0x80);  // 1101 0111 | 1000 0000 = 1101 0111 
  inByte = SPI.transfer(0x00);
  digitalWrite(GYRO_CS, HIGH);  
  SPI.endTransaction(); 
  return inByte;
  
}

void writeRegister(int8_t thisRegister, int8_t val){
  SPI.beginTransaction(SPISettings(10000000, MSBFIRST, SPI_MODE0));
  digitalWrite(GYRO_CS, LOW);
  SPI.transfer(thisRegister << 1);
  SPI.transfer(val);
  digitalWrite(GYRO_CS, HIGH);
  SPI.endTransaction();
}

Any help would be much appreciated! I've been staring at this for a while and I need a different set of eyes.

2

SPISettings should be done in setup(), if it is needed at all. I can't imagine what happens with the above, or that it is a good idea.

Take a look at SPI examples from other IMU libraries. You might find this Sparkfun guide to be helpful: LSM9DS0 Hookup Guide - SparkFun Learn

Or better, just use the Pololu library. It should work "out of the box": L3G - Arduino Reference

3

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