AP_RCProtocol: add support for DJI Fast SBUS

It's just SBUS... but with increased opportunities for corruption

libraries/AP_RCProtocol/AP_RCProtocol.cpp

@@ -39,12 +39,15 @@ void AP_RCProtocol::init()
 {
     backend[AP_RCProtocol::PPM] = new AP_RCProtocol_PPMSum(*this);
     backend[AP_RCProtocol::IBUS] = new AP_RCProtocol_IBUS(*this);
-    backend[AP_RCProtocol::SBUS] = new AP_RCProtocol_SBUS(*this, true);
+    backend[AP_RCProtocol::SBUS] = new AP_RCProtocol_SBUS(*this, true, 100000);
+#if AP_RCPROTOCOL_FASTSBUS_ENABLED
+    backend[AP_RCProtocol::FASTSBUS] = new AP_RCProtocol_SBUS(*this, true, 200000);
+#endif
     backend[AP_RCProtocol::DSM] = new AP_RCProtocol_DSM(*this);
     backend[AP_RCProtocol::SUMD] = new AP_RCProtocol_SUMD(*this);
     backend[AP_RCProtocol::SRXL] = new AP_RCProtocol_SRXL(*this);
 #ifndef IOMCU_FW
-    backend[AP_RCProtocol::SBUS_NI] = new AP_RCProtocol_SBUS(*this, false);
+    backend[AP_RCProtocol::SBUS_NI] = new AP_RCProtocol_SBUS(*this, false, 100000);
     backend[AP_RCProtocol::SRXL2] = new AP_RCProtocol_SRXL2(*this);
     backend[AP_RCProtocol::CRSF] = new AP_RCProtocol_CRSF(*this);
     backend[AP_RCProtocol::FPORT2] = new AP_RCProtocol_FPort2(*this, true);
@@ -257,6 +260,10 @@ static const AP_RCProtocol::SerialConfig serial_configs[] {
     { 115200,  0,   1, true },
     // SBUS settings, even parity, 2 stop bits:
     { 100000,  2,   2, true },
+#if AP_RCPROTOCOL_FASTSBUS_ENABLED
+    // FastSBUS:
+    { 200000,  2,   2, true },
+#endif
     // CrossFire:
     { 416666,  0,   1, false },
 };
@@ -389,6 +396,10 @@ const char *AP_RCProtocol::protocol_name_from_protocol(rcprotocol_t protocol)
     case SBUS:
     case SBUS_NI:
         return "SBUS";
+#if AP_RCPROTOCOL_FASTSBUS_ENABLED
+    case FASTSBUS:
+        return "FastSBUS";
+#endif
     case DSM:
         return "DSM";
     case SUMD:

libraries/AP_RCProtocol/AP_RCProtocol.h

@@ -21,6 +21,14 @@
 #define MAX_RCIN_CHANNELS 18
 #define MIN_RCIN_CHANNELS  5
 
+#ifndef AP_RCPROTOCOL_FASTSBUS_ENABLED
+  #ifdef IOMCU_FW
+    #define AP_RCPROTOCOL_FASTSBUS_ENABLED 0
+  #else
+    #define AP_RCPROTOCOL_FASTSBUS_ENABLED 1
+  #endif
+#endif
+
 class AP_RCProtocol_Backend;
 
 class AP_RCProtocol {
@@ -42,6 +50,9 @@ public:
         ST24       =  9,
         FPORT      = 10,
         FPORT2     = 11,
+#if AP_RCPROTOCOL_FASTSBUS_ENABLED
+        FASTSBUS   = 12,
+#endif
         NONE    //last enum always is None
     };
     void init();
@@ -64,6 +75,9 @@ public:
     bool requires_3_frames(enum rcprotocol_t p) {
         switch (p) {
         case DSM:
+#if AP_RCPROTOCOL_FASTSBUS_ENABLED
+        case FASTSBUS:
+#endif
         case SBUS:
         case SBUS_NI:
         case PPM:

libraries/AP_RCProtocol/AP_RCProtocol_SBUS.cpp

@@ -76,9 +76,10 @@
 #endif
 
 // constructor
-AP_RCProtocol_SBUS::AP_RCProtocol_SBUS(AP_RCProtocol &_frontend, bool _inverted) :
+AP_RCProtocol_SBUS::AP_RCProtocol_SBUS(AP_RCProtocol &_frontend, bool _inverted, uint32_t configured_baud) :
     AP_RCProtocol_Backend(_frontend),
-    inverted(_inverted)
+    inverted(_inverted),
+    ss{configured_baud, SoftSerial::SERIAL_CONFIG_8E2I}
 {}
 
 // decode a full SBUS frame
@@ -211,7 +212,9 @@ void AP_RCProtocol_SBUS::_process_byte(uint32_t timestamp_us, uint8_t b)
 // support byte input
 void AP_RCProtocol_SBUS::process_byte(uint8_t b, uint32_t baudrate)
 {
-    if (baudrate != 100000) {
+    // note that if we're here we're not actually using SoftSerial,
+    // but it does record our configured baud rate:
+    if (baudrate != ss.baud()) {
         return;
     }
     _process_byte(AP_HAL::micros(), b);

libraries/AP_RCProtocol/AP_RCProtocol_SBUS.h

@@ -22,7 +22,7 @@
 
 class AP_RCProtocol_SBUS : public AP_RCProtocol_Backend {
 public:
-    AP_RCProtocol_SBUS(AP_RCProtocol &_frontend, bool inverted);
+    AP_RCProtocol_SBUS(AP_RCProtocol &_frontend, bool inverted, uint32_t configured_baud);
     void process_pulse(uint32_t width_s0, uint32_t width_s1) override;
     void process_byte(uint8_t byte, uint32_t baudrate) override;
 
@@ -32,7 +32,7 @@ private:
                      bool *sbus_failsafe, bool *sbus_frame_drop, uint16_t max_values);
 
     bool inverted;
-    SoftSerial ss{100000, SoftSerial::SERIAL_CONFIG_8E2I};
+    SoftSerial ss;
     uint32_t saved_width;
 
     struct {

libraries/AP_RCProtocol/SoftSerial.h

@@ -33,6 +33,8 @@ public:
         return byte_timestamp_us;
     }
 
+    uint32_t baud() const { return baudrate; }
+
 private:
     const uint32_t baudrate;
     const uint8_t half_bit; // width of half a bit in microseconds

libraries/RC_Channel/RC_Channels_VarInfo.h

@@ -96,7 +96,7 @@ const AP_Param::GroupInfo RC_Channels::var_info[] = {
     // @DisplayName: RC protocols enabled
     // @Description: Bitmask of enabled RC protocols. Allows narrowing the protocol detection to only specific types of RC receivers which can avoid issues with incorrect detection. Set to 1 to enable all protocols.
     // @User: Advanced
-    // @Bitmask: 0:All,1:PPM,2:IBUS,3:SBUS,4:SBUS_NI,5:DSM,6:SUMD,7:SRXL,8:SRXL2,9:CRSF,10:ST24,11:FPORT,12:FPORT2
+    // @Bitmask: 0:All,1:PPM,2:IBUS,3:SBUS,4:SBUS_NI,5:DSM,6:SUMD,7:SRXL,8:SRXL2,9:CRSF,10:ST24,11:FPORT,12:FPORT2,13:FastSBUS
     AP_GROUPINFO("_PROTOCOLS", 34, RC_CHANNELS_SUBCLASS, _protocols, 1),
     
     AP_GROUPEND