HAL_Linux: support inverted 115200 protocols

this allows for FrSky FPort input

libraries/AP_HAL_Linux/RCInput_RCProtocol.cpp

@@ -24,6 +24,7 @@
 #include <sys/ioctl.h>
 #include <asm/termbits.h>
 #include "RCInput_RCProtocol.h"
+#include <GCS_MAVLink/GCS.h>
 
 #if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_DISCO || \
     CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BLUE
@@ -102,43 +103,44 @@ int RCInput_RCProtocol::open_115200(const char *path)
 }
 
 // constructor
-RCInput_RCProtocol::RCInput_RCProtocol(const char *_dev_sbus, const char *_dev_115200) :
-    dev_sbus(_dev_sbus),
+RCInput_RCProtocol::RCInput_RCProtocol(const char *_dev_inverted, const char *_dev_115200) :
+    dev_inverted(_dev_inverted),
     dev_115200(_dev_115200)
 {
 }
 
 void RCInput_RCProtocol::init()
 {
-    if (dev_sbus) {
-        fd_sbus = open_sbus(dev_sbus);
+    if (dev_inverted) {
+        fd_inverted = open_sbus(dev_inverted);
     } else {
-        fd_sbus = -1;
+        fd_inverted = -1;
     }
+    inverted_is_115200 = false;
     if (dev_115200) {
         fd_115200 = open_115200(dev_115200);
     } else {
         fd_115200 = -1;
     }
     AP::RC().init();
-    printf("SBUS FD %d  115200 FD %d\n", fd_sbus, fd_115200);
+    printf("SBUS FD %d  115200 FD %d\n", fd_inverted, fd_115200);
 }
 
 void RCInput_RCProtocol::_timer_tick(void)
 {
-    uint8_t b[40];
+    uint8_t b[80];
 
-    if (fd_sbus != -1) {
-        ssize_t n = ::read(fd_sbus, &b[0], sizeof(b));
+    if (fd_inverted != -1) {
+        ssize_t n = ::read(fd_inverted, &b[0], sizeof(b));
         if (n > 0) {
             for (uint8_t i=0; i<n; i++) {
-                AP::RC().process_byte(b[i], 100000);
+                AP::RC().process_byte(b[i], inverted_is_115200?115200:100000);
             }
         }
     }
     if (fd_115200 != -1) {
         ssize_t n = ::read(fd_115200, &b[0], sizeof(b));
-        if (n > 0) {
+        if (n > 0 && !inverted_is_115200) {
             for (uint8_t i=0; i<n; i++) {
                 AP::RC().process_byte(b[i], 115200);
             }
@@ -146,6 +148,7 @@ void RCInput_RCProtocol::_timer_tick(void)
     }
 
     if (AP::RC().new_input()) {
+        last_frame_ms = AP_HAL::millis();
         uint8_t n = AP::RC().num_channels();
         for (uint8_t i=0; i<n; i++) {
             _pwm_values[i] = AP::RC().read(i);
@@ -153,6 +156,19 @@ void RCInput_RCProtocol::_timer_tick(void)
         _num_channels = n;
         rc_input_count++;
     }
+
+    uint32_t now = AP_HAL::millis();
+    if (fd_inverted != -1 && now - last_frame_ms > 2000) {
+        // no inverted data for 2s, flip baudrate
+        close(fd_inverted);
+        inverted_is_115200 = !inverted_is_115200;
+        if (inverted_is_115200) {
+            fd_inverted = open_115200(dev_inverted);
+        } else {
+            fd_inverted = open_sbus(dev_inverted);
+        }
+        last_frame_ms = now;
+    }
 }
 
 #endif // HAL

libraries/AP_HAL_Linux/RCInput_RCProtocol.h

@@ -38,11 +38,13 @@ private:
     int open_sbus(const char *path);
     int open_115200(const char *path);
 
-    const char *dev_sbus;
+    const char *dev_inverted;
     const char *dev_115200;
 
-    int fd_sbus;
+    int fd_inverted;
     int fd_115200;
+    uint32_t last_frame_ms;
+    bool inverted_is_115200;
 };
 };