* companion_radio_usb: encoding in ArduinoSerialInterface changed to 16-bit frame lengths

* MAX_FRAME_SIZE now 172 (to fit max 160 byte text msg)

src/helpers/ArduinoSerialInterface.cpp

@@ -1,8 +1,9 @@
 #include "ArduinoSerialInterface.h"
 
-#define RECV_STATE_IDLE       0
-#define RECV_STATE_HDR_FOUND  1
-#define RECV_STATE_LEN_FOUND  2
+#define RECV_STATE_IDLE        0
+#define RECV_STATE_HDR_FOUND   1
+#define RECV_STATE_LEN1_FOUND  2
+#define RECV_STATE_LEN2_FOUND  3
 
 void ArduinoSerialInterface::enable() { 
   _isEnabled = true;
@@ -26,10 +27,12 @@ size_t ArduinoSerialInterface::writeFrame(const uint8_t src[], size_t len) {
     return 0;
   }
 
-  uint8_t hdr[2];
+  uint8_t hdr[3];
   hdr[0] = '>';
-  hdr[1] = len;
-  _serial->write(hdr, 2);
+  hdr[1] = (len & 0xFF);  // LSB
+  hdr[2] = (len >> 8);    // MSB
+
+  _serial->write(hdr, 3);
   return _serial->write(src, len);
 }
 
@@ -45,9 +48,13 @@ size_t ArduinoSerialInterface::checkRecvFrame(uint8_t dest[]) {
         }
         break;
       case RECV_STATE_HDR_FOUND:
-        _frame_len = (uint8_t)c;
+        _frame_len = (uint8_t)c;   // LSB
+        _state = RECV_STATE_LEN1_FOUND;
+        break;
+      case RECV_STATE_LEN1_FOUND:
+        _frame_len |= ((uint16_t)c) << 8;   // MSB
         rx_len = 0;
-        _state = _frame_len > 0 ? RECV_STATE_LEN_FOUND : RECV_STATE_IDLE;
+        _state = _frame_len > 0 ? RECV_STATE_LEN2_FOUND : RECV_STATE_IDLE;
         break;
       default:
         if (rx_len < MAX_FRAME_SIZE) {

src/helpers/ArduinoSerialInterface.h

@@ -6,8 +6,8 @@
 class ArduinoSerialInterface : public BaseSerialInterface {
   bool _isEnabled;
   uint8_t _state;
-  uint8_t _frame_len;
-  uint8_t rx_len;
+  uint16_t _frame_len;
+  uint16_t rx_len;
   HardwareSerial* _serial;
   uint8_t rx_buf[MAX_FRAME_SIZE];
 

src/helpers/BaseSerialInterface.h

@@ -2,7 +2,7 @@
 
 #include <Arduino.h>
 
-#define MAX_FRAME_SIZE  160
+#define MAX_FRAME_SIZE  172
 
 class BaseSerialInterface {
 protected: