Hi,
I am trying to communicate with the MPU-6500 from InvenSense and the STM32F405 micro controller in SPI.I managed to read the WHO AM I. And seems to respond well with its value of 0x70.
The problem I have is when I want to read the accelerometer and gyroscope values I get random values.
Here are the SPI configurations:
Prescale to 32 to have a baud rate of 500Kbit/s (Maximum frequecny at 1Mhz) / CPOL to High /Clock Phase: 2 Edge.
Here are the characteristics of the MPU6500 :
And finally here is the code that I have for these different operations :
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_SPI3_Init(void);
static void MX_USART3_UART_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
#define CS_SELECT 0
#define CS_DESELECT 1
#define READWRITE 0x80
#define SPI_TIMOUT_MS 1000
#define PWR_MGMT_1 0x6B
#define USER_CTRL 0x6A
#define CONFIG 0x1A
#define GYRO_CONFIG 0x1B
#define WHO_AM_I 0x75
#define WHO_AM_I_6500_ANS 0x70
#define ACCEL_XOUT_H 0x3B
#define GYRO_ZOUT_H 0x47
#define GYRO_ZOUT_L 0x48
#define ACCEL_XOUT_H 0x3B
#define ACCEL_XOUT_L 0x3C
#define LP_ACCEL_ODR 0x1E
#define SIGNAL_PATH_RESET 0x68
float GYRO_FACTOR=16.4;
#define TRUE 1
#define FALSE 0
uint8_t readByte(uint8_t reg)
{
uint8_t rx_data[2];
uint8_t tx_data[2];
tx_data[0] = reg | 0x80;
tx_data[1] = 0x00; // dummy
HAL_SPI_TransmitReceive(&hspi3, tx_data, rx_data, 2, 1);
return rx_data[1];
}
void writeByte(uint8_t reg, uint8_t data)
{
uint8_t rx_data[2];
uint8_t tx_data[2];
tx_data[0] = reg & 0x7F;
tx_data[1] = data; // write data
HAL_SPI_TransmitReceive(&hspi3, tx_data, rx_data, 2, 1);
}
uint8_t MPU_begin()
{
// Initialize variables
uint8_t addr, val;
uint8_t who_am_i = 0;
// Confirm device
who_am_i = readByte( WHO_AM_I );
printf( "0x%x \n",who_am_i );
if (who_am_i == WHO_AM_I_6500_ANS)
{
// Startup / reset the sensor
addr = PWR_MGMT_1;
val = 0x80;
writeByte(addr,val);
HAL_Delay(100);
addr = SIGNAL_PATH_RESET;
val = 0x07;
// writeByte(addr,val);
HAL_Delay(100);
// Disable FSYNC
addr = CONFIG;
val = 0x00;
writeByte(addr,val);
HAL_Delay(50);
//Config gyro 2000dps -> 2000dps : 16.4dps = 1deg/s
addr = GYRO_CONFIG;
val = 0x00;
writeByte(addr,val);
HAL_Delay(50);
//Config freqence Acc
addr = LP_ACCEL_ODR;
val = 0x00;
writeByte(addr,val);
HAL_Delay(50);
return 1;
}
else
{
return 0;
}
}
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
int16_t accel_x_value;
int16_t accel_y_value;
int16_t accel_z_value;
float accel_x;
float accel_y;
float accel_z;
int16_t gyro_x_value;
int16_t gyro_y_value;
int16_t gyro_z_value;
float gyro_x_ang_vel;
float gyro_y_ang_vel;
float gyro_z_ang_vel;
int16_t temp_value;
float temp;
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_SPI3_Init();
MX_USART3_UART_Init();
/* USER CODE BEGIN 2 */
if (MPU_begin() != TRUE)
{
printf("ERROR SPI Communication!\r\n");
while (1){}
}else{
printf("MPU6500 - OK\n");
}
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
// ACCELEROMETER MEASUREMENT ACCEL_XOUT_H & ACCEL_XOUT_L
accel_x_value = ( ((int16_t)readByte(0x3B)<<8) | ((int16_t)readByte(0x3C)&0x00ff) );
accel_x = (float)accel_x_value / 16384;
printf("ACCEL_XOUT = %6d[Raw] = %6.3lf[g]\n\r", accel_x_value, accel_x);
// ACCELEROMETER MEASUREMENT ACCEL_YOUT_H & ACCEL_YOUT_L
accel_y_value = ( ((int16_t)readByte(0x3D)<<8) | ((int16_t)readByte(0x3E)&0x00ff) );
accel_y = (float)accel_y_value / 16384;
printf("ACCEL_YOUT = %6d[Raw] = %6.3lf[g]\n\r", accel_y_value, accel_y);
// ACCELEROMETER MEASUREMENT ACCEL_ZOUT_H & ACCEL_ZOUT_L
accel_z_value = ( ((int16_t)readByte(0x3F)<<8) | ((int16_t)readByte(0x40)&0x00ff) );
accel_z = (float)accel_z_value / 16384;
printf("ACCEL_ZOUT = %6d[Raw] = %6.3lf[g]\n\r", accel_z_value, accel_z);
// GYROSCOPE MEASUREMENT GYRO_XOUT_H & GYRO_XOUT_L
gyro_x_value = ( ((int16_t)readByte(0x43)<<8) | ((int16_t)readByte(0x44)&0x00ff) );
gyro_x_ang_vel = (float)gyro_x_value / 131;
printf(" GYRO_XOUT = %5d[Raw] = %8.3lf[deg/s]\n\r", gyro_x_value, gyro_x_ang_vel);
// GYROSCOPE MEASUREMENT GYRO_YOUT_H & GYRO_YOUT_L
gyro_y_value = ( ((int16_t)readByte(0x45)<<8) | ((int16_t)readByte(0x46)&0x00ff) );
gyro_y_ang_vel = (float)gyro_y_value / 131;
printf(" GYRO_YOUT = %5d[Raw] = %8.3lf[deg/s]\n\r", gyro_y_value, gyro_y_ang_vel);
// GYROSCOPE MEASUREMENT GYRO_ZOUT_H & GYRO_ZOUT_L
gyro_z_value = ( ((int16_t)readByte(0x47)<<8) | ((int16_t)readByte(0x48)&0x00ff) );
gyro_z_ang_vel = (float)gyro_z_value / 131;
printf(" GYRO_ZOUT = %5d[Raw] = %8.3lf[deg/s]\n\r", gyro_z_value, gyro_z_ang_vel);
// TEMPERATURE MEASUREMENT GYRO_ZOUT_H & GYRO_ZOUT_L
temp_value = ( ((int16_t)readByte(0x41)<<8) | ((int16_t)readByte(0x42)&0x00ff) );
temp = (float)temp_value / 326.8 + 25.0;
printf(" TEMP_OUT = %5d[Raw] = %3.1lf[℃]\n\r", temp_value, temp);
HAL_Delay(10);
}
/* USER CODE END 3 */
}
Do you know why I have these random values? Thanks in advance
Sincerely
You're not doing anything with CS. Bring CS low before the start of the transaction and high afterwards. Initialize it and control it as a GPIO output pin.
I would also guess the data registers are meant to be read in one single transaction. If you read 6 bytes from 0x3B, you will get addressed 0x3B, 0x3C, 0x3D, etc...
