AP_IOMCU: support IMU heater

libraries/AP_IOMCU/AP_IOMCU.cpp

@@ -71,6 +71,7 @@ enum ioevents {
     IOEVENT_SET_RATES,
     IOEVENT_GET_RCIN,
     IOEVENT_ENABLE_SBUS,
+    IOEVENT_SET_HEATER_TARGET,
 };
 
 // setup page registers
@@ -90,6 +91,7 @@ enum ioevents {
 #define PAGE_REG_SETUP_DEFAULTRATE   3
 #define PAGE_REG_SETUP_ALTRATE       4
 #define PAGE_REG_SETUP_SBUS_RATE    19
+#define PAGE_REG_SETUP_HEATER_DUTY_CYCLE 21
 
 #define PAGE_REG_SETUP_FORCE_SAFETY_OFF 12
 #define PAGE_REG_SETUP_FORCE_SAFETY_ON  14
@@ -198,6 +200,13 @@ void AP_IOMCU::thread_main(void)
                 continue;                
             }
         }
+
+        if (mask & EVENT_MASK(IOEVENT_SET_HEATER_TARGET)) {
+            if (!write_register(PAGE_SETUP, PAGE_REG_SETUP_HEATER_DUTY_CYCLE, heater_duty_cycle)) {
+                event_failed(IOEVENT_SET_HEATER_TARGET);
+                continue;
+            }
+        }
         
         // check for regular timed events
         uint32_t now = AP_HAL::millis();
@@ -513,4 +522,11 @@ bool AP_IOMCU::check_rcinput(uint32_t &last_frame_us, uint8_t &num_channels, uin
     return false;
 }
 
+// set IMU heater target
+void AP_IOMCU::set_heater_duty_cycle(uint8_t duty_cycle)
+{
+    heater_duty_cycle = duty_cycle;
+    trigger_event(IOEVENT_SET_HEATER_TARGET);
+}
+
 #endif // HAL_WITH_IO_MCU

libraries/AP_IOMCU/AP_IOMCU.h

@@ -63,7 +63,10 @@ public:
       get rssi voltage
      */
     float get_vrssi(void) const { return reg_status.vrssi * 0.001; }
-    
+
+    // set target for IMU heater
+    void set_heater_duty_cycle(uint8_t duty_cycle);
+
 private:
     AP_HAL::UARTDriver &uart;
 
@@ -173,6 +176,9 @@ private:
         uint16_t default_freq = 50;
         uint16_t sbus_rate_hz;
     } rate;
+
+    // IMU heater duty cycle
+    uint8_t heater_duty_cycle;
     
     bool corked;
 };