Make request buffer size configurable.

Author: batt

src/ModbusRTUServer.cpp

@@ -34,7 +34,7 @@ ModbusRTUServerClass::~ModbusRTUServerClass()
 {
 }
 
-int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config)
+int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config, unsigned max_req_size)
 {
   modbus_t* mb = modbus_new_rtu(baudrate, config);
 
@@ -43,13 +43,14 @@ int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config)
   }
 
   modbus_connect(mb);
+  _max_request_size = max_req_size;
 
   return 1;
 }
 
 void ModbusRTUServerClass::poll()
 {
-  uint8_t request[MODBUS_RTU_MAX_ADU_LENGTH];
+  uint8_t request[_max_request_size];
 
   int requestLength = modbus_receive(_mb, request);
 

src/ModbusRTUServer.h

@@ -21,6 +21,7 @@
 #define _MODBUS_RTU_SERVER_H_INCLUDED
 
 #include "ModbusServer.h"
+#include "libmodbus/modbus-rtu.h"
 
 class ModbusRTUServerClass : public ModbusServer {
 public:
@@ -36,12 +37,14 @@ class ModbusRTUServerClass : public ModbusServer {
    *
    * Return 1 on success, 0 on failure
    */
-  int begin(int id, unsigned long baudrate, uint16_t config = SERIAL_8N1);
+  int begin(int id, unsigned long baudrate, uint16_t config = SERIAL_8N1, unsigned max_req_size = MODBUS_RTU_MAX_ADU_LENGTH);
 
   /**
    * Poll interface for requests
    */
   virtual void poll();
+private:
+  unsigned _max_request_size;
 };
 
 extern ModbusRTUServerClass ModbusRTUServer;