AP_InertialSensor: support ICM-20689 IMU

like the 20789, but without the baro

libraries/AP_InertialSensor/AP_InertialSensor_Backend.h

@@ -102,7 +102,8 @@ public:
         DEVTYPE_GYR_MPU9250  = 0x24,
         DEVTYPE_GYR_I3G4250D = 0x25,
         DEVTYPE_GYR_LSM9DS1  = 0x26,
-        DEVTYPE_INS_ICM20789 = 0x27
+        DEVTYPE_INS_ICM20789 = 0x27,
+        DEVTYPE_INS_ICM20689 = 0x28,
     };
         
 protected:

libraries/AP_InertialSensor/AP_InertialSensor_Invensense.cpp

@@ -215,6 +215,10 @@ void AP_InertialSensor_Invensense::start()
         gdev = DEVTYPE_INS_ICM20789;
         adev = DEVTYPE_INS_ICM20789;
         break;
+    case Invensense_ICM20689:
+        gdev = DEVTYPE_INS_ICM20689;
+        adev = DEVTYPE_INS_ICM20689;
+        break;
     }
 
     /*
@@ -243,6 +247,10 @@ void AP_InertialSensor_Invensense::start()
         temp_zero = 25;
         temp_sensitivity = 0.003;
         break;
+    case Invensense_ICM20689:
+        temp_zero = 25;
+        temp_sensitivity = 0.003;
+        break;
     }
 
     _gyro_instance = _imu.register_gyro(1000, _dev->get_bus_id_devtype(gdev));
@@ -693,7 +701,7 @@ void AP_InertialSensor_Invensense::_set_filter_register(void)
             // setup for 4kHz accels
             _register_write(ICMREG_ACCEL_CONFIG2, ICM_ACC_FCHOICE_B, true);
         } else {
-            uint8_t fifo_size = (_mpu_type == Invensense_ICM20789) ? 1:0;
+            uint8_t fifo_size = (_mpu_type == Invensense_ICM20789 || _mpu_type == Invensense_ICM20689) ? 1:0;
             _register_write(ICMREG_ACCEL_CONFIG2, ICM_ACC_DLPF_CFG_218HZ | (fifo_size<<6), true);
         }
     }
@@ -726,6 +734,9 @@ bool AP_InertialSensor_Invensense::_check_whoami(void)
     case MPU_WHOAMI_ICM20789_R1:
         _mpu_type = Invensense_ICM20789;
         return true;
+    case MPU_WHOAMI_ICM20689:
+        _mpu_type = Invensense_ICM20689;
+        return true;
     }
     // not a value WHOAMI result
     return false;

libraries/AP_InertialSensor/AP_InertialSensor_Invensense.h

@@ -63,6 +63,7 @@ public:
         Invensense_ICM20608,
         Invensense_ICM20602,
         Invensense_ICM20789,
+        Invensense_ICM20689,
     };
     
 private:

libraries/AP_InertialSensor/AP_InertialSensor_Invensense_registers.h

@@ -174,6 +174,7 @@
 #define MPU_WHOAMI_MPU9255      0x73
 #define MPU_WHOAMI_ICM20789     0x03
 #define MPU_WHOAMI_ICM20789_R1  0x02
+#define MPU_WHOAMI_ICM20689     0x98
 
 #define BIT_READ_FLAG                           0x80
 #define BIT_I2C_SLVX_EN                         0x80