* added helpers/ArduinoSerialInterface, for the 'companion radio'

* .ini, target envs: Heltec_v3_companion_radio_usb &  Heltec_v3_companion_radio_ble

src/helpers/ArduinoSerialInterface.cpp

@@ -0,0 +1,66 @@
+#include "ArduinoSerialInterface.h"
+
+#define RECV_STATE_IDLE       0
+#define RECV_STATE_HDR_FOUND  1
+#define RECV_STATE_LEN_FOUND  2
+
+void ArduinoSerialInterface::enable() { 
+  _isEnabled = true;
+  _state = RECV_STATE_IDLE;
+}
+void ArduinoSerialInterface::disable() {
+  _isEnabled = false;
+}
+
+bool ArduinoSerialInterface::isConnected() const { 
+  return true;   // no way of knowing, so assume yes
+}
+
+bool ArduinoSerialInterface::isWriteBusy() const {
+  return false;
+}
+
+size_t ArduinoSerialInterface::writeFrame(const uint8_t src[], size_t len) {
+  if (len > MAX_FRAME_SIZE) {
+    // frame is too big!
+    return 0;
+  }
+
+  uint8_t hdr[2];
+  hdr[0] = '>';
+  hdr[1] = len;
+  _serial->write(hdr, 2);
+  return _serial->write(src, len);
+}
+
+size_t ArduinoSerialInterface::checkRecvFrame(uint8_t dest[]) {
+  while (_serial->available()) {
+    int c = _serial->read();
+    if (c < 0) break;
+
+    switch (_state) {
+      case RECV_STATE_IDLE:
+        if (c == '<') {
+          _state = RECV_STATE_HDR_FOUND;
+        }
+        break;
+      case RECV_STATE_HDR_FOUND:
+        _frame_len = (uint8_t)c;
+        rx_len = 0;
+        _state = _frame_len > 0 ? RECV_STATE_LEN_FOUND : RECV_STATE_IDLE;
+        break;
+      default:
+        if (rx_len < MAX_FRAME_SIZE) {
+          rx_buf[rx_len] = (uint8_t)c;   // rest of frame will be discarded if > MAX
+        }
+        rx_len++;
+        if (rx_len >= _frame_len) {  // received a complete frame?
+          if (_frame_len > MAX_FRAME_SIZE) _frame_len = MAX_FRAME_SIZE;    // truncate
+          memcpy(dest, rx_buf, _frame_len);
+          _state = RECV_STATE_IDLE;  // reset state, for next frame
+          return _frame_len;
+        }
+    }
+  }
+  return 0;
+}

src/helpers/ArduinoSerialInterface.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "BaseSerialInterface.h"
+#include <Arduino.h>
+
+class ArduinoSerialInterface : public BaseSerialInterface {
+  bool _isEnabled;
+  uint8_t _state;
+  uint8_t _frame_len;
+  uint8_t rx_len;
+  HardwareSerial* _serial;
+  uint8_t rx_buf[MAX_FRAME_SIZE];
+
+public:
+  ArduinoSerialInterface() { _isEnabled = false; _state = 0; }
+
+  void begin(HardwareSerial& serial) { _serial = &serial; }
+
+  // BaseSerialInterface methods
+  void enable() override;
+  void disable() override;
+  bool isEnabled() const override { return _isEnabled; }
+
+  bool isConnected() const override;
+
+  bool isWriteBusy() const override;
+  size_t writeFrame(const uint8_t src[], size_t len) override;
+  size_t checkRecvFrame(uint8_t dest[]) override;
+};