modbus support

lib/ModbusMaster/examples/Basic/Basic.pde

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+/*
+
+  Basic.pde - example using ModbusMaster library
+
+  Library:: ModbusMaster
+  Author:: Doc Walker <4-20ma@wvfans.net>
+
+  Copyright:: 2009-2016 Doc Walker
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+#include <ModbusMaster.h>
+
+
+// instantiate ModbusMaster object
+ModbusMaster node;
+
+
+void setup()
+{
+  // use Serial (port 0); initialize Modbus communication baud rate
+  Serial.begin(19200);
+
+  // communicate with Modbus slave ID 2 over Serial (port 0)
+  node.begin(2, Serial);
+}
+
+
+void loop()
+{
+  static uint32_t i;
+  uint8_t j, result;
+  uint16_t data[6];
+  
+  i++;
+  
+  // set word 0 of TX buffer to least-significant word of counter (bits 15..0)
+  node.setTransmitBuffer(0, lowWord(i));
+  
+  // set word 1 of TX buffer to most-significant word of counter (bits 31..16)
+  node.setTransmitBuffer(1, highWord(i));
+  
+  // slave: write TX buffer to (2) 16-bit registers starting at register 0
+  result = node.writeMultipleRegisters(0, 2);
+  
+  // slave: read (6) 16-bit registers starting at register 2 to RX buffer
+  result = node.readHoldingRegisters(2, 6);
+  
+  // do something with data if read is successful
+  if (result == node.ku8MBSuccess)
+  {
+    for (j = 0; j < 6; j++)
+    {
+      data[j] = node.getResponseBuffer(j);
+    }
+  }
+}