altos: Document which MPU6000 revs have broken accel values

From Tridge -- MPU6000 rev C4 and C5 are broken, having accelerometer
values in the wrong range. This commit just adds comments which note
this; experimentation will be required to actually sort out what's
going on.

Signed-off-by: Keith Packard <keithp@keithp.com>

2 files changed, 55 insertions, 0 deletions

diff --git a/src/drivers/ao_mpu6000.c b/src/drivers/ao_mpu6000.c
index 49596705..6d47482c 100644
--- a/src/drivers/ao_mpu6000.c
+++ b/src/drivers/ao_mpu6000.c
@@ -199,6 +199,24 @@ ao_mpu6000_setup(void)
 	ao_delay(AO_MS_TO_TICKS(200));
 	ao_mpu6000_sample(&test_mode);
 
+#if TRIDGE
+	// read the product ID rev c has 1/2 the sensitivity of rev d
+    _mpu6000_product_id = _register_read(MPUREG_PRODUCT_ID);
+    //Serial.printf("Product_ID= 0x%x\n", (unsigned) _mpu6000_product_id);
+
+    if ((_mpu6000_product_id == MPU6000ES_REV_C4) || (_mpu6000_product_id == MPU6000ES_REV_C5) ||
+        (_mpu6000_product_id == MPU6000_REV_C4) || (_mpu6000_product_id == MPU6000_REV_C5)) {
+        // Accel scale 8g (4096 LSB/g)
+        // Rev C has different scaling than rev D
+        register_write(MPUREG_ACCEL_CONFIG,1<<3);
+    } else {
+        // Accel scale 8g (4096 LSB/g)
+        register_write(MPUREG_ACCEL_CONFIG,2<<3);
+    }
+    hal.scheduler->delay(1);
+
+#endif
+
 	/* Configure accelerometer to +/-16G */
 	ao_mpu6000_reg_write(MPU6000_ACCEL_CONFIG,
 			     (0 << MPU600_ACCEL_CONFIG_XA_ST) |
diff --git a/src/drivers/ao_mpu6000.h b/src/drivers/ao_mpu6000.h
index 6aada9a9..f01e9e83 100644
--- a/src/drivers/ao_mpu6000.h
+++ b/src/drivers/ao_mpu6000.h
@@ -21,6 +21,27 @@
 #define MPU6000_ADDR_WRITE	0xd0
 #define MPU6000_ADDR_READ	0xd1
 
+/* From Tridge */
+#define MPUREG_XG_OFFS_TC 0x00
+#define MPUREG_YG_OFFS_TC 0x01
+#define MPUREG_ZG_OFFS_TC 0x02
+#define MPUREG_X_FINE_GAIN 0x03
+#define MPUREG_Y_FINE_GAIN 0x04
+#define MPUREG_Z_FINE_GAIN 0x05
+#define MPUREG_XA_OFFS_H 0x06 // X axis accelerometer offset (high byte)
+#define MPUREG_XA_OFFS_L 0x07 // X axis accelerometer offset (low byte)
+#define MPUREG_YA_OFFS_H 0x08 // Y axis accelerometer offset (high byte)
+#define MPUREG_YA_OFFS_L 0x09 // Y axis accelerometer offset (low byte)
+#define MPUREG_ZA_OFFS_H 0x0A // Z axis accelerometer offset (high byte)
+#define MPUREG_ZA_OFFS_L 0x0B // Z axis accelerometer offset (low byte)
+#define MPUREG_PRODUCT_ID 0x0C // Product ID Register
+#define MPUREG_XG_OFFS_USRH 0x13 // X axis gyro offset (high byte)
+#define MPUREG_XG_OFFS_USRL 0x14 // X axis gyro offset (low byte)
+#define MPUREG_YG_OFFS_USRH 0x15 // Y axis gyro offset (high byte)
+#define MPUREG_YG_OFFS_USRL 0x16 // Y axis gyro offset (low byte)
+#define MPUREG_ZG_OFFS_USRH 0x17 // Z axis gyro offset (high byte)
+#define MPUREG_ZG_OFFS_USRL 0x18 // Z axis gyro offset (low byte)
+
 #define MPU6000_SMPRT_DIV	0x19
 
 #define MPU6000_CONFIG		0x1a
@@ -163,4 +184,20 @@ extern struct ao_mpu6000_sample	ao_mpu6000_current;
 void
 ao_mpu6000_init(void);
 
+/* Product ID Description for MPU6000
+ * high 4 bits low 4 bits
+ * Product Name Product Revision
+ */
+#define MPU6000ES_REV_C4 0x14	/* 0001 0100 */
+#define MPU6000ES_REV_C5 0x15	/* 0001 0101 */
+#define MPU6000ES_REV_D6 0x16	/* 0001 0110 */
+#define MPU6000ES_REV_D7 0x17	/* 0001 0111 */
+#define MPU6000ES_REV_D8 0x18	/* 0001 1000 */
+#define MPU6000_REV_C4 0x54	/* 0101 0100 */
+#define MPU6000_REV_C5 0x55	/* 0101 0101 */
+#define MPU6000_REV_D6 0x56	/* 0101 0110 */
+#define MPU6000_REV_D7 0x57	/* 0101 0111 */
+#define MPU6000_REV_D8 0x58	/* 0101 1000 */
+#define MPU6000_REV_D9 0x59	/* 0101 1001 */
+
 #endif /* _AO_MPU6000_H_ */