MPU 60X0 Sample Code

[sapan]

Hi,

Code is part of my project. Right now its for I2C1. Prior to calling any of these function you need to initialize I2C1.

One sample part to read accelerometer, temperature sensor and gyro data. I have tested this code on MPU6000 and MPU6050 on I2C bus.

Code: Select all

  set_mpu_sample_rate(9);
  set_mpu_config_regsiter(EXT_SYNC_SET0, DLPF_CFG0);
  set_mpu_gyro(XG_ST_DIS, YG_ST_DIS, ZG_ST_DIS, FS_SEL_250);
  set_mpu_accel(XA_ST_DIS, YA_ST_DIS, ZA_ST_DIS, AFS_SEL_2g, ACCEL_HPF0);
  set_mpu_power_mgmt1(DEVICE_RESET_DIS, SLEEP_DIS, CYCLE_DIS, TEMPERATURE_EN, CLKSEL_XG);
  set_mpu_user_control(USER_FIFO_DIS, I2C_MST_DIS, I2C_IF_DIS, FIFO_RESET_DIS, I2C_MST_RESET_DIS, SIG_COND_RESET_DIS);

  write_mpu_power_mgmt1();
  write_mpu_gyro();
  write_mpu_accel();
  write_mpu_sample_rate();
  while (TRUE) {
     mpu_i2c_read_data(0x3B, 14); /* Read accelerometer, temperature and gyro data */
     chThdSleepMilliseconds(50);
  }

Still this is work in progress. It sends data over UART in mpu60x0.c file. First three values are accelerometer, fourth one is temperature sensor and last three are gyro values. Havent explored FIFO and interrupt part yet.
Waiting for feedbacks.


Sapan

[barthess]

Hi sapan,
This device uses two’s complement data format. Using shift/addition operations for acquiring data is incorrect.
I use following function.

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int16_t complement2signed(uint8_t msb, uint8_t lsb){
  uint16_t word = 0;
  word = (msb << 8) + lsb;
  if (msb > 0x7F){
    return -1 * ((int16_t)((~word) + 1));
  }
  return (int16_t)word;
}

[sapan]

I have checked output and it give correct data as per orientation of the sensor. I mean as mentioned in data sheet (Apart from resolution, which is less because its engineering samples).

[barthess]

In my cases shift produces correct results for positive values, but negative values are incorrect.

[sapan]

Thats weird, it should work fine. I am using eclipse + arm-none-eabi-gdb toolchain to compile ChibiOS. Btw I am using part of your BMP085 sample code to interface with BMP180. Will post that once commenting and cleaning up my part.

[barthess]

May be your device actually outputs data in different format than my ITG3200, but datasheet on MPU-6xxx says "Output in two’s complement format" too.

[sapan]

Yup I have used this device via LPC2138 as well as Discovery board. On LPC2138 I programmed it using basic code (no RTOS) but used similar method over there and it worked fine. Discovery board I am using ChibiOS. I have used both MPU6000 and MPU6050 gives same outputs.

[sapan]

Any comments about code??

[barthess]

For my cases it is overengineered. I use hardcoded values in my project for sampling rate, LPF, etc., that are suitable enough.

[sapan]

ok...can do one thing... declare some default values which will be used...so no need to initialize them.