add LUA access to serial port (serial2 and USB)

radio/src/lua/api_general.cpp

@@ -1280,6 +1280,44 @@ static int luaResetGlobalTimer(lua_State * L)
   return 0;
 }
 
+/*luadoc
+@function serialWrite(str)
+@param str (string) String to be written to the serial port.
+
+Writes a string to the serial port. The string is allowed to contain any character, including 0.
+
+@status current Introducted in TODO
+*/
+static int luaSerialWrite(lua_State * L)
+{
+  const char * str = luaL_checkstring(L, 1);
+  size_t len = lua_rawlen(L, 1);
+
+  if (!str || len < 1)
+    return 0;
+
+#if !defined(SIMU)
+  #if defined(USB_SERIAL)
+  if (getSelectedUsbMode() == USB_SERIAL_MODE) {
+    size_t wr_len = len;
+    const char* p = str;
+    while(wr_len--) usbSerialPutc(*p++);
+  }
+  #endif
+  #if defined(SERIAL2)
+  if (serial2Mode == UART_MODE_LUA) {
+    size_t wr_len = len;
+    const char* p = str;
+    while(wr_len--) serial2Putc(*p++);
+  }
+  #endif
+#else
+  debugPrintf("luaSerialWrite: %.*s",len,str);
+#endif
+
+  return 0;
+}
+
 const luaL_Reg opentxLib[] = {
   { "getTime", luaGetTime },
   { "getDateTime", luaGetDateTime },
@@ -1318,6 +1356,7 @@ const luaL_Reg opentxLib[] = {
   { "crossfireTelemetryPop", luaCrossfireTelemetryPop },
   { "crossfireTelemetryPush", luaCrossfireTelemetryPush },
 #endif
+  { "serialWrite", luaSerialWrite },
   { NULL, NULL }  /* sentinel */
 };