HAL_Linux: support SRXL R/C input

libraries/AP_HAL_Linux/RCInput.cpp

@@ -14,6 +14,7 @@
 #include <AP_HAL/utility/dsm.h>
 #include <AP_HAL/utility/sumd.h>
 #include <AP_HAL/utility/st24.h>
+#include <AP_HAL/utility/srxl.h>
 
 #include "RCInput.h"
 #include "sbus.h"
@@ -464,6 +465,30 @@ void RCInput::add_st24_input(const uint8_t *bytes, size_t nbytes)
     }
 }
 
+/*
+  add some bytes of input in SRXL serial stream format, coping with partial packets
+ */
+void RCInput::add_srxl_input(const uint8_t *bytes, size_t nbytes)
+{
+    uint16_t values[LINUX_RC_INPUT_NUM_CHANNELS];
+    uint8_t channel_count;
+    uint64_t now = AP_HAL::micros64();
+    
+    while (nbytes > 0) {
+        if (srxl_decode(now, *bytes++, &channel_count, values, LINUX_RC_INPUT_NUM_CHANNELS) == 0) {
+            if (channel_count > LINUX_RC_INPUT_NUM_CHANNELS) {
+                return;
+            }
+            for (uint8_t i=0; i<channel_count; i++) {
+                _pwm_values[i] = values[i];
+            }
+            _num_channels = channel_count;
+            new_rc_input = true;
+        }
+        nbytes--;
+    }
+}
+
 
 /*
   add some bytes of input in SBUS serial stream format, coping with partial packets

libraries/AP_HAL_Linux/RCInput.h

@@ -39,6 +39,9 @@ public:
 
     // add some st24 input bytes, for RCInput over a serial port
     void add_st24_input(const uint8_t *bytes, size_t nbytes);
+
+    // add some srxl input bytes, for RCInput over a serial port
+    void add_srxl_input(const uint8_t *bytes, size_t nbytes);
     
 protected:
     void _process_rc_pulse(uint16_t width_s0, uint16_t width_s1);

libraries/AP_HAL_Linux/RCInput_115200.cpp

@@ -31,9 +31,6 @@
 #include <errno.h>
 #include <sys/ioctl.h>
 #include <termios.h>
-#include <AP_HAL/utility/sumd.h>
-#include <AP_HAL/utility/st24.h>
-#include <AP_HAL/utility/dsm.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -105,6 +102,9 @@ void RCInput_115200::_timer_tick(void)
         return;
     }
 
+    // process as srxl
+    add_srxl_input(bytes, nread);
+
     // process as DSM
     add_dsm_input(bytes, nread);