AP_HAL: added voltage_latest() interface

this will be used for reading the 5V rail

libraries/AP_HAL/AnalogIn.h

@@ -28,6 +28,10 @@ public:
     // against a reference voltage
     virtual float voltage_average() = 0;
 
+    // return a voltage from 0.0 to 5.0V, scaled
+    // against a reference voltage
+    virtual float voltage_latest() = 0;
+
     // return a voltage from 0.0 to 5.0V, assuming a ratiometric
     // sensor
     virtual float voltage_average_ratiometric() = 0;

libraries/AP_HAL_AVR_SITL/AnalogIn.cpp

@@ -24,6 +24,10 @@ float ADCSource::voltage_average() {
 	return (5.0f/1023.0f) * read_average();
 }
 
+float ADCSource::voltage_latest() {
+	return (5.0f/1023.0f) * read_latest();
+}
+
 float ADCSource::read_latest() {
     switch (_pin) {
     case ANALOG_INPUT_BOARD_VCC:

libraries/AP_HAL_AVR_SITL/AnalogIn.h

@@ -19,6 +19,7 @@ public:
     float read_latest();
     void set_pin(uint8_t p);
     float voltage_average();
+    float voltage_latest();
     float voltage_average_ratiometric() { return voltage_average(); }
     void set_stop_pin(uint8_t pin) {}
     void set_settle_time(uint16_t settle_time_ms) {}

libraries/AP_HAL_Empty/AnalogIn.cpp

@@ -14,6 +14,10 @@ float EmptyAnalogSource::voltage_average() {
     return 5.0 * _v / 1024.0;
 }
 
+float EmptyAnalogSource::voltage_latest() {
+    return 5.0 * _v / 1024.0;
+}
+
 float EmptyAnalogSource::read_latest() {
     return _v;
 }

libraries/AP_HAL_Empty/AnalogIn.h

@@ -13,6 +13,7 @@ public:
     void set_stop_pin(uint8_t p);
     void set_settle_time(uint16_t settle_time_ms);
     float voltage_average();
+    float voltage_latest();
     float voltage_average_ratiometric() { return voltage_average(); }
 private:
     float _v;

libraries/AP_HAL_SMACCM/AnalogIn.cpp

@@ -16,6 +16,11 @@ float SMACCMAnalogSource::voltage_average() {
     return (5.0/1024.0) * read_average();
 }
 
+float SMACCMAnalogSource::voltage_latest() {
+    // this assumes 5.0V scaling and 1024 range
+    return (5.0/1024.0) * read_latest();
+}
+
 float SMACCMAnalogSource::read_latest() {
     return _v;
 }

libraries/AP_HAL_SMACCM/AnalogIn.h

@@ -11,6 +11,7 @@ public:
     float read_latest();
     void set_pin(uint8_t p);
     float voltage_average();
+    float voltage_latest();
     float voltage_average_ratiometric() { return voltage_average(); }
     void set_stop_pin(uint8_t p) {}
     void set_settle_time(uint16_t settle_time_ms) {}