AP_HAL_PX4: support SBusOut

add unbuffered writes and uart config

libraries/AP_HAL_PX4/RCOutput.cpp

@@ -574,7 +574,7 @@ void PX4RCOutput::timer_tick(void)
 /*
   enable sbus output
  */
-bool PX4RCOutput::enable_sbus_out(uint16_t rate_hz)
+bool PX4RCOutput::enable_px4io_sbus_out(uint16_t rate_hz)
 {
     int fd = open("/dev/px4io", 0);
     if (fd == -1) {

libraries/AP_HAL_PX4/RCOutput.h

@@ -38,7 +38,7 @@ public:
     void set_output_mode(enum output_mode mode) override;
 
     void timer_tick(void) override;
-    bool enable_sbus_out(uint16_t rate_hz) override;
+    bool enable_px4io_sbus_out(uint16_t rate_hz) override;
 
     // set default output update rate
     void set_default_rate(uint16_t rate_hz) override;

libraries/AP_HAL_PX4/UARTDriver.cpp

@@ -28,7 +28,8 @@ PX4UARTDriver::PX4UARTDriver(const char *devpath, const char *perf_name) :
     _in_timer(false),
     _perf_uart(perf_alloc(PC_ELAPSED, perf_name)),
     _os_start_auto_space(-1),
-    _flow_control(FLOW_CONTROL_DISABLE)
+    _flow_control(FLOW_CONTROL_DISABLE),
+    _unbuffered_writes(false)
 {
 }
 
@@ -153,6 +154,44 @@ void PX4UARTDriver::set_flow_control(enum flow_control fcontrol)
     _flow_control = fcontrol;
 }
 
+void PX4UARTDriver::configure_parity(uint8_t v) {
+    if (_fd == -1) {
+        return;
+    }
+    struct termios t;
+    tcgetattr(_fd, &t);
+    if (v != 0) {
+        // enable parity
+        t.c_cflag |= PARENB;
+        if (v == 1) {
+            t.c_cflag |= PARODD;
+        } else {
+            t.c_cflag &= ~PARODD;
+        }
+    }
+    else {
+        // disable parity
+        t.c_cflag &= ~PARENB;
+    }
+    tcsetattr(_fd, TCSANOW, &t);
+}
+
+void PX4UARTDriver::set_stop_bits(int n) {
+    if (_fd == -1) {
+        return;
+    }
+    struct termios t;
+    tcgetattr(_fd, &t);
+    if (n > 1) t.c_cflag |= CSTOPB;
+    else t.c_cflag &= ~CSTOPB;
+    tcsetattr(_fd, TCSANOW, &t);
+}
+
+bool PX4UARTDriver::set_unbuffered_writes(bool on) {
+    _unbuffered_writes = on;
+    return _unbuffered_writes;
+}
+
 void PX4UARTDriver::begin(uint32_t b)
 {
 	begin(b, 0, 0);
@@ -256,7 +295,7 @@ int16_t PX4UARTDriver::read()
 }
 
 /*
-   write one byte to the buffer
+   write one byte
  */
 size_t PX4UARTDriver::write(uint8_t c)
 {
@@ -268,6 +307,11 @@ size_t PX4UARTDriver::write(uint8_t c)
         return 0;
     }
 
+    if (_unbuffered_writes) {
+        // write one byte to the file descriptor
+        return _write_fd(&c, 1);
+    }
+
     while (_writebuf.space() == 0) {
         if (_nonblocking_writes) {
             return 0;
@@ -278,7 +322,7 @@ size_t PX4UARTDriver::write(uint8_t c)
 }
 
 /*
-  write size bytes to the write buffer
+ * write size bytes
  */
 size_t PX4UARTDriver::write(const uint8_t *buffer, size_t size)
 {
@@ -302,6 +346,11 @@ size_t PX4UARTDriver::write(const uint8_t *buffer, size_t size)
         return ret;
     }
 
+    if (_unbuffered_writes) {
+        // write buffer straight to the file descriptor
+        return _write_fd(buffer, size);
+    }
+
     return _writebuf.write(buffer, size);
 }
 

libraries/AP_HAL_PX4/UARTDriver.h

@@ -39,6 +39,10 @@ public:
     void set_flow_control(enum flow_control flow_control);
     enum flow_control get_flow_control(void) { return _flow_control; }
 
+    void configure_parity(uint8_t v);
+    void set_stop_bits(int n);
+    bool set_unbuffered_writes(bool on);
+
 private:
     const char *_devpath;
     int _fd;
@@ -47,6 +51,7 @@ private:
     volatile bool _in_timer;
 
     bool _nonblocking_writes;
+    bool _unbuffered_writes;
 
     // we use in-task ring buffers to reduce the system call cost
     // of ::read() and ::write() in the main loop