Return flag from poll() to allow conditional events to trigger

Author: nsted

examples/RTU/ModbusRTUServerLED/ModbusRTUServerLED.ino

@@ -44,16 +44,18 @@ void setup() {
 
 void loop() {
   // poll for Modbus RTU requests
-  ModbusRTUServer.poll();
-
-  // read the current value of the coil
-  int coilValue = ModbusRTUServer.coilRead(0x00);
-
-  if (coilValue) {
-    // coil value set, turn LED on
-    digitalWrite(ledPin, HIGH);
-  } else {
-    // coil value clear, turn LED off
-    digitalWrite(ledPin, LOW);
+  int packetReceived = ModbusRTUServer.poll();
+
+  if(packetReceived) {
+    // read the current value of the coil
+    int coilValue = ModbusRTUServer.coilRead(0x00);
+  
+    if (coilValue) {
+      // coil value set, turn LED on
+      digitalWrite(ledPin, HIGH);
+    } else {
+      // coil value clear, turn LED off
+      digitalWrite(ledPin, LOW);
+    }
   }
 }

src/ModbusRTUServer.cpp

@@ -47,15 +47,17 @@ int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config)
   return 1;
 }
 
-void ModbusRTUServerClass::poll()
+int ModbusRTUServerClass::poll()
 {
   uint8_t request[MODBUS_RTU_MAX_ADU_LENGTH];
 
   int requestLength = modbus_receive(_mb, request);
 
   if (requestLength > 0) {
     modbus_reply(_mb, request, requestLength, &_mbMapping);
+    return 1;
   }
+  return 0;
 }
 
 ModbusRTUServerClass ModbusRTUServer;

src/ModbusRTUServer.h

@@ -41,7 +41,7 @@ class ModbusRTUServerClass : public ModbusServer {
   /**
    * Poll interface for requests
    */
-  virtual void poll();
+  virtual int poll();
 };
 
 extern ModbusRTUServerClass ModbusRTUServer;

src/ModbusServer.h

@@ -126,8 +126,10 @@ class ModbusServer {
 
   /**
    * Poll for requests
+   * 
+   * @return 1 on request, 0 on no request.
    */
-  virtual void poll() = 0;
+  virtual int poll() = 0;
 
   /**
    * Stop the server

src/ModbusTCPServer.cpp

@@ -57,7 +57,7 @@ void ModbusTCPServer::accept(Client& client)
   }
 }
 
-void ModbusTCPServer::poll()
+int ModbusTCPServer::poll()
 {
   if (_client != NULL) {
     uint8_t request[MODBUS_TCP_MAX_ADU_LENGTH];
@@ -66,6 +66,8 @@ void ModbusTCPServer::poll()
 
     if (requestLength > 0) {
       modbus_reply(_mb, request, requestLength, &_mbMapping);
+      return 1;
     }
   }
+  return 0;
 }

src/ModbusTCPServer.h

@@ -48,7 +48,7 @@ class ModbusTCPServer : public ModbusServer {
   /**
    * Poll accepted client for requests
    */
-  virtual void poll();
+  virtual int poll();
 
 private:
   Client* _client;