Copter: ported RSSI_PIN option from ArduPlane

this is useful for OSD users

ArduCopter/ArduCopter.pde

@@ -440,6 +440,9 @@ static int8_t control_mode = STABILIZE;
 // This is set to -1 when we need to re-read the switch
 static byte oldSwitchPosition;
 
+// receiver RSSI
+static uint8_t receiver_rssi;
+
 
 ////////////////////////////////////////////////////////////////////////////////
 // Motor Output
@@ -890,6 +893,10 @@ static uint8_t save_trim_counter;
 // Reference to the AP relay object - APM1 only
 AP_Relay relay;
 
+// a pin for reading the receiver RSSI voltage. The scaling by 0.25 
+// is to take the 0 to 1024 range down to an 8 bit range for MAVLink
+AP_AnalogSource_Arduino RSSI_pin(-1, 0.25);
+
 #if CLI_ENABLED == ENABLED
     static int8_t   setup_show (uint8_t argc, const Menu::arg *argv);
 #endif
@@ -1105,7 +1112,7 @@ static void medium_loop()
     //------------------------------------------------
     case 1:
         medium_loopCounter++;
-
+        read_receiver_rssi();
         break;
 
     // command processing

ArduCopter/GCS_Mavlink.pde

@@ -295,7 +295,6 @@ static void NOINLINE send_gps_raw(mavlink_channel_t chan)
 
 static void NOINLINE send_servo_out(mavlink_channel_t chan)
 {
-    const uint8_t rssi = 1;
     // normalized values scaled to -10000 to 10000
     // This is used for HIL.  Do not change without discussing with HIL maintainers
 
@@ -313,7 +312,7 @@ static void NOINLINE send_servo_out(mavlink_channel_t chan)
         0,
         0,
         0,
-        rssi);
+        receiver_rssi);
 #else
  #if X_PLANE == ENABLED
     /* update by JLN for X-Plane HIL */
@@ -330,7 +329,7 @@ static void NOINLINE send_servo_out(mavlink_channel_t chan)
             10000 * g.rc_2.norm_output(),
             10000 * g.rc_3.norm_output(),
             10000 * g.rc_4.norm_output(),
-            rssi);
+            receiver_rssi);
     }else{
         mavlink_msg_rc_channels_scaled_send(
             chan,
@@ -344,7 +343,7 @@ static void NOINLINE send_servo_out(mavlink_channel_t chan)
             10000 * g.rc_2.norm_output(),
             10000 * g.rc_3.norm_output(),
             10000 * g.rc_4.norm_output(),
-            rssi);
+            receiver_rssi);
     }
 
  #else
@@ -360,14 +359,13 @@ static void NOINLINE send_servo_out(mavlink_channel_t chan)
         10000 * g.rc_2.norm_output(),
         10000 * g.rc_3.norm_output(),
         10000 * g.rc_4.norm_output(),
-        rssi);
+        receiver_rssi);
  #endif
 #endif
 }
 
 static void NOINLINE send_radio_in(mavlink_channel_t chan)
 {
-    const uint8_t rssi = 1;
     mavlink_msg_rc_channels_raw_send(
         chan,
         millis(),
@@ -380,7 +378,7 @@ static void NOINLINE send_radio_in(mavlink_channel_t chan)
         g.rc_6.radio_in,
         g.rc_7.radio_in,
         g.rc_8.radio_in,
-        rssi);
+        receiver_rssi);
 }
 
 static void NOINLINE send_radio_out(mavlink_channel_t chan)

ArduCopter/Parameters.h

@@ -70,6 +70,7 @@ public:
                                                         // 2 = med, 3 = slow
 
         k_param_crosstrack_min_distance,
+        k_param_rssi_pin,
 
         // 65: AP_Limits Library
         k_param_limits = 65,
@@ -262,6 +263,7 @@ public:
 
     AP_Int8         battery_volt_pin;
     AP_Int8         battery_curr_pin;
+    AP_Int8         rssi_pin;
 
     // Waypoints
     //

ArduCopter/Parameters.pde

@@ -137,6 +137,13 @@ const AP_Param::Info var_info[] PROGMEM = {
     // @User: Standard
     GSCALAR(battery_curr_pin,    "BATT_CURR_PIN",    BATTERY_CURR_PIN),
 
+    // @Param: RSSI_PIN
+    // @DisplayName: Receiver RSSI sensing pin
+    // @Description: This selects an analog pin for the receiver RSSI voltage. It assumes the voltage is 5V for max rssi, 0V for minimum
+    // @Values: -1:Disabled, 0:A0, 1:A1, 2:A2, 13:A13
+    // @User: Standard
+    GSCALAR(rssi_pin,            "RSSI_PIN",         -1),
+
     GSCALAR(waypoint_mode,  "WP_MODE",          0),
     GSCALAR(command_total,  "WP_TOTAL",         0),
     GSCALAR(command_index,  "WP_INDEX",         0),

ArduCopter/sensors.pde

@@ -104,3 +104,12 @@ static void read_battery(void)
         low_battery_counter = 0;
     }
 }
+
+// read the receiver RSSI as an 8 bit number for MAVLink
+// RC_CHANNELS_SCALED message
+void read_receiver_rssi(void)
+{
+    RSSI_pin.set_pin(g.rssi_pin);
+    float ret = RSSI_pin.read();
+    receiver_rssi = constrain(ret, 0, 255);
+}