HAL_Linux: added basic support for RC overrides

this allows for easier testing of RC output by allowing
mavproxy to setup fake inputs

Pair-Programmed-With: Sid, Anuj, Victor and Philip

libraries/AP_HAL_Linux/RCInput.cpp

@@ -5,42 +5,71 @@
 #include "RCInput.h"
 
 using namespace Linux;
-LinuxRCInput::LinuxRCInput()
+LinuxRCInput::LinuxRCInput() :
+new_rc_input(false)
 {}
 
 void LinuxRCInput::init(void* machtnichts)
 {}
 
-bool LinuxRCInput::new_input() {
+bool LinuxRCInput::new_input() 
+{
+    return new_rc_input;
+}
+
+uint8_t LinuxRCInput::num_channels() 
+{
+    return 8;
+}
+
+uint16_t LinuxRCInput::read(uint8_t ch) 
+{
+    new_rc_input = false;
+    if (_override[ch]) {
+        return _override[ch];
+    }
+    if (ch == 2) {
+        // force low throttle for now
+        return 900;
+    }
+    return 1500;
+}
+
+uint8_t LinuxRCInput::read(uint16_t* periods, uint8_t len) 
+{
+    for (uint8_t i=0; i<len; i++) {
+	periods[i] = read(i);
+    }
+    return 8;
+}
+
+bool LinuxRCInput::set_overrides(int16_t *overrides, uint8_t len) 
+{
+    bool res = false;
+    for (uint8_t i = 0; i < len; i++) {
+        res |= set_override(i, overrides[i]);
+    }
+    return res;
+}
+
+bool LinuxRCInput::set_override(uint8_t channel, int16_t override) 
+{
+    if (override < 0) return false; /* -1: no change. */
+    if (channel < 8) {
+        _override[channel] = override;
+        if (override != 0) {
+            new_rc_input = true;
+            return true;
+        }
+    }
     return false;
 }
 
-uint8_t LinuxRCInput::num_channels() {
-    return 0;
-}
-
-uint16_t LinuxRCInput::read(uint8_t ch) {
-    if (ch == 2) return 900; /* throttle should be low, for safety */
-    else return 1500;
-}
-
-uint8_t LinuxRCInput::read(uint16_t* periods, uint8_t len) {
-    for (uint8_t i = 0; i < len; i++){
-        if (i == 2) periods[i] = 900;
-        else periods[i] = 1500;
-    }
-    return len;
-}
-
-bool LinuxRCInput::set_overrides(int16_t *overrides, uint8_t len) {
-    return true;
-}
-
-bool LinuxRCInput::set_override(uint8_t channel, int16_t override) {
-    return true;
-}
-
 void LinuxRCInput::clear_overrides()
-{}
+{
+    for (uint8_t i = 0; i < 8; i++) {
+	_override[i] = 0;
+    }
+}
 
 #endif // CONFIG_HAL_BOARD

libraries/AP_HAL_Linux/RCInput.h

@@ -16,6 +16,12 @@ public:
     bool set_overrides(int16_t *overrides, uint8_t len);
     bool set_override(uint8_t channel, int16_t override);
     void clear_overrides();
+
+ private:
+    bool new_rc_input;
+
+    /* override state */
+    uint16_t _override[8];
 };
 
 #endif // __AP_HAL_LINUX_RCINPUT_H__