fix arduino not sending data to the COM-port

src/arduino_messenger.cpp

@@ -17,7 +17,15 @@ arduino_messenger::arduino_messenger(
 		throw open_error(error.message().c_str());
 	}
 
-	com.set_option(net::serial_port_base::baud_rate(baud_rate));
+	com.set_option(
+		net::serial_port_base::baud_rate(baud_rate)
+	);
+	// enable DTR (Data Terminal Ready) for reading from the COM-port to work
+	com.set_option(
+		net::serial_port_base::flow_control(
+			net::serial_port_base::flow_control::hardware
+		)
+	);
 }
 
 void arduino_messenger::run() {
@@ -29,7 +37,9 @@ void arduino_messenger::run() {
 }
 
 void arduino_messenger::do_read() {
-	net::async_read_until(com, buffer, '%',
+	net::streambuf::mutable_buffers_type temp_mut_buf = buffer.prepare(MAX_MESSAGE_LENGTH);
+
+	com.async_read_some(net::buffer(temp_mut_buf),
 		beast::bind_front_handler(
 			&arduino_messenger::on_read,
 			shared_from_this()
@@ -45,9 +55,16 @@ void arduino_messenger::on_read(
 		return;
 	}
 
-	auto buffer_data = buffer.data();
+	buffer.commit(bytes_transferred);
+
+	std::string message(
+		reinterpret_cast<const char*>(buffer.data().data()), 
+		buffer.data().size()
+	);
+
+	buffer.consume(bytes_transferred);
 
-	std::string message(reinterpret_cast<const char*>(buffer_data.data()), buffer_data.size());
+	std::cout << "Read message: " << message << std::endl;
 
 	std::lock_guard lock(imq_mutex);
 	incoming_message_queue.push(json_message::parse_message(message));
@@ -57,7 +74,7 @@ void arduino_messenger::on_read(
 
 void arduino_messenger::do_write() {
 	if (!outgoing_message_queue.empty()) {
-		outgoing_message_buffer = outgoing_message_queue.front().dump_message() + '%';
+		outgoing_message_buffer = outgoing_message_queue.front().dump_message();
 		outgoing_message_queue.pop();
 
 		std::cout << "Sending message: " << outgoing_message_buffer << std::endl;

src/arduino_messenger.hpp

@@ -7,11 +7,14 @@
 #include <boost/asio/error.hpp>
 #include <boost/asio/placeholders.hpp>
 #include <boost/asio/read_until.hpp>
+#include <boost/asio/read.hpp>
 #include "json_message.hpp"
 #include <queue>
 #include <thread>
 
 class arduino_messenger : public std::enable_shared_from_this<arduino_messenger> {
+	static constexpr std::size_t MAX_MESSAGE_LENGTH = 100;
+
 	net::serial_port com;
 	net::streambuf buffer;
 

src/arduino_program/gate_control/gate_control.ino

@@ -1,56 +1,57 @@
 #include <ArduinoJson.h>
+
+static const char* TYPE = "type";
+static const char* PAYLOAD = "payload";
+static const char* CHANGE_STATE = "change_state";
+static const char* QUERY_STATE = "query_state";
+static const char* QUERY_STATE_RESULT = "query_state_result";
+
 const int capacity = 100;
 StaticJsonDocument<capacity> doc;
 bool state = false;
 
-void setup() {
-  Serial.begin(115200);
-  pinMode(13, OUTPUT);
-  digitalWrite(13, LOW);
-}
+void change_state(bool new_state, bool persist_change = true) {
+  if (persist_change) {
+    state = new_state;
+  }
 
-void flash() {
-  digitalWrite(13, HIGH);
-  delay(200);
-  digitalWrite(13, LOW);
-  delay(200);
-  digitalWrite(13, HIGH);
-  delay(200);
-  digitalWrite(13, LOW);
-  delay(200);
-  if (state) {
+  if (new_state) {
     digitalWrite(13, HIGH);
   } else {
     digitalWrite(13, LOW);
   }
 }
 
+void setup() {
+  Serial.begin(115200);
+  Serial.setTimeout(50);
+  pinMode(13, OUTPUT);
+  change_state(false);
+}
+
 void loop() {
   if (Serial.available() > 0) {
-    String msg = Serial.readStringUntil('%');
-    // skip the message end character
-    Serial.read();
+    String msg = Serial.readString();
 
     deserializeJson(doc, msg);
-    if (doc["type"] == "change_state" && doc["payload"] == true) {
-      digitalWrite(13, HIGH);
-      state = true;
-    } else if (doc["type"] == "change_state" && doc["payload"] == false) {
-      digitalWrite(13, LOW);
-      state = false;
-    } else if (doc["type"] == "query_state") {
+
+    if (doc[TYPE] == CHANGE_STATE) {
+      if (doc[PAYLOAD] == true) {
+        change_state(true);
+      } else if (doc[PAYLOAD] == false) {
+        change_state(false);
+      }
+    } else if (doc[TYPE] == QUERY_STATE) {
       DynamicJsonDocument dyn_doc(100);
-      dyn_doc["type"] = "query_state_result";
-      dyn_doc["payload"] = state;
+      dyn_doc[TYPE] = QUERY_STATE_RESULT;
+      dyn_doc[PAYLOAD] = state;
+
       String msg;
       serializeJson(dyn_doc, msg);
-      msg += '%';
-
-      flash();
 
       Serial.write(msg.c_str());
     } else {
-      Serial.write("{\"type\": \"error\", \"payload\": \"unknown_command\"}%");
+      Serial.write("{\"type\": \"error\", \"payload\": \"unknown_command\"}");
     }
   }
 }