imuboard: add some comments in mpu6050, clean is needed...

diff --git a/imuboard/mpu6050.c b/imuboard/mpu6050.c
index a149f5d493f6b4c403353d614cb1a799bd3eec10..0cec567e5ffd74060197da5da30702fa0ea52239 100644 (file)
--- a/imuboard/mpu6050.c
+++ b/imuboard/mpu6050.c
@@ -46,16 +46,19 @@
 
 // fs_sel = 3
 // 2000°/s
-#define gyro_x_resolution 16.4
-#define gyro_y_resolution 16.4
-#define gyro_z_resolution 16.4
+/* #define gyro_x_resolution 16.4 */
+/* #define gyro_y_resolution 16.4 */
+/* #define gyro_z_resolution 16.4 */
+// XXX it works with 32.8, why?
+#define gyro_x_resolution 32.8
+#define gyro_y_resolution 32.8
+#define gyro_z_resolution 32.8
 
 #define accel_x_resolution 2048.0
 #define accel_y_resolution 2048.0
 #define accel_z_resolution 2048.0
 
 #define MPU6050_ADDRESS 0x69
-#define MPU6050_MAGNETO_ADDRESS 0x0D
 
 #define SWAP_16(a) ((( (a) & 0xff)<<8) | (( (a) >> 8) & 0xff))
 
@@ -134,10 +137,13 @@ uint8_t mpu6050_read_all_axes(struct imu_info *imu)
        imu->gy = ToRad((double)(axes[5] - drift_g[1]) / gyro_y_resolution);
        imu->gz = ToRad((double)(axes[6] - drift_g[2]) / gyro_z_resolution);
 
+       /* output data resolution is 13 bit (0.3 μT per LSB) */
        imu->mx = (double) axes[7] * 0.3;
        imu->my = (double) axes[8] * 0.3;
        imu->mz = (double) axes[9] * 0.3;
 
+       //printf("%4.4x %4.4x %4.4x\n", axes[7], axes[8], axes[9]);
+
        return err;
 }
 
@@ -206,42 +212,50 @@ static void mpu6050_compute_drift(void)
 
 static uint8_t setup_mpu9150_magneto(void)
 {
-       //uint8_t i, err;
-
-       //MPU9150_I2C_ADDRESS = 0x0C;      //change Adress to Compass
-
-       /* XXX doesn't work, no answer from magneto */
-       /* for (i = 0; i < 127; i++) { */
-       /*      printf_P(PSTR("i=%d\r\n"), i); */
-       /*      err = send_mpu6050_cmd(i, 0x0A, 0x00); //PowerDownMode */
-
-       /*      if (err == 0) */
-       /*              printf_P(PSTR("COIN\r\n")); */
-       /* } */
-       send_mpu6050_cmd(MPU6050_MAGNETO_ADDRESS, 0x0A, 0x00); //PowerDownMode
-       send_mpu6050_cmd(MPU6050_MAGNETO_ADDRESS, 0x0A, 0x0F); //SelfTest
-       send_mpu6050_cmd(MPU6050_MAGNETO_ADDRESS, 0x0A, 0x00); //PowerDownMode
-
-       //MPU9150_I2C_ADDRESS = 0x69;      //change Adress to MPU
+       /* here we configure the mpu9150 to poll the magnetometer.
+        * See "MPU-9150 Register Map and Descriptions" section 4.14 */
 
+       /* When the WAIT_FOR_ES bit is set to 1, the Data Ready interrupt will
+        * be delayed until External Sensor data from the Slave Devices are
+        * loaded into the EXT_SENS_DATA registers. This is used to */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x24, 0x40); //Wait for Data at Slave0
+
+       /* slave0: ask to read 6 bytes from reg 0x3 (start of magneto data, see
+        * section 5) of device 0xC */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x25, 0x8C); //Set i2c address at slave0 at 0x0C
-       //send_mpu6050_cmd(MPU6050_ADDRESS, 0x26, 0x02); //Set where reading at slave 0 starts
-       send_mpu6050_cmd(MPU6050_ADDRESS, 0x26, 0x03); //Set where reading at slave 0 starts
-       //send_mpu6050_cmd(MPU6050_ADDRESS, 0x27, 0x88); //set offset at start reading and enable
+       send_mpu6050_cmd(MPU6050_ADDRESS, 0x26, 0x03); //Set where reading at slave 0 starts // 3
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x27, 0x86); //set offset at start reading and enable
+
+       /* slave1: ask to write 1 byte (value = 0x01 = single measurement mode)
+        * at 0xA (control register) of device 0xC */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x28, 0x0C); //set i2c address at slv1 at 0x0C
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x29, 0x0A); //Set where reading at slave 1 starts
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x2A, 0x81); //Enable at set length to 1
-       send_mpu6050_cmd(MPU6050_ADDRESS, 0x64, 0x01); //overvride register
+       send_mpu6050_cmd(MPU6050_ADDRESS, 0x64, 0x01); //direction of slave1 write
+
+       /* enable reduced rate on slave 0 and slave 1 */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x67, 0x03); //set delay rate
+
+       /* XXX ? */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x01, 0x80);
 
+       /* set i2c master delay, XXX move before? */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x34, 0x04); //set i2c slv4 delay
+
+       /* XXX useless */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x64, 0x00); //override register
+
+       /* disable i2c master, the auxiliary I2C bus lines (AUX_DA and AUX_CL)
+        * are logically driven by the primary I2C bus (SDA and SCL). */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x6A, 0x00); //clear usr setting
+
+       /* XXX useless */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x64, 0x01); //override register
+
+       /* enable i2c master mode */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x6A, 0x20); //enable master i2c mode
+
+       /* change again XXX the i2c master delay */
        send_mpu6050_cmd(MPU6050_ADDRESS, 0x34, 0x13); //disable slv4
 
        return 0;
@@ -262,7 +276,7 @@ int8_t mpu6050_init(void)
                        break;
        }
 
-       /* XX use one of the gyro for clock ref: if we don't do that, some i2c
+       /* XXX use one of the gyro for clock ref: if we don't do that, some i2c
         * commands fail... why ?? */
        send_mpu6050_cmd(MPU6050_ADDRESS, MPU6050_RA_PWR_MGMT_1, 0b00000010);
 
@@ -278,6 +292,12 @@ int8_t mpu6050_init(void)
        /* Disable accel self tests, scale of +-16g, no DHPF */
        send_mpu6050_cmd(MPU6050_ADDRESS, MPU6050_RA_ACCEL_CONFIG, 0b00011000);
 
+
+       /* XXX all is set to 0, useless?
+          The reset value is 0x00 for all registers other than the registers below.
+          • Register 107: 0x40.
+          • Register 117: 0x68.
+       */
        /* Freefall threshold of <|0mg| */
        send_mpu6050_cmd(MPU6050_ADDRESS, MPU6050_RA_FF_THR, 0x00);
        /* Freefall duration limit of 0 */