Merge pull request #66 from kintel/halfduplex-example

Added half duplex RS485 example

examples/RS485_HalfDuplex/RS485_HalfDuplex.ino

@@ -0,0 +1,96 @@
+/*
+
+  RS485_HalfDuplex.pde - example using ModbusMaster library
+
+  This example is tested against an EPSolar LS2024B solar charge controller.
+  See here for protocol specs:
+  http://www.solar-elektro.cz/data/dokumenty/1733_modbus_protocol.pdf
+
+  This file is part of ModbusMaster.
+  
+  ModbusMaster is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+  
+  ModbusMaster is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+  
+  You should have received a copy of the GNU General Public License
+  along with ModbusMaster.  If not, see <http://www.gnu.org/licenses/>.
+  
+  Written by Marius Kintel <marius at kintel dot net>
+  
+*/
+#include <ModbusMaster.h>
+
+/*!
+  We're using a MAX485-compatible RS485 Transceiver.
+  Rx/Tx is hooked up to the hardware serial port at 'Serial'.
+  The Data Enable and Receiver Enable pins are hooked up as follows:
+*/
+#define MAX485_DE      3
+#define MAX485_RE_NEG  2
+
+// instantiate ModbusMaster object
+ModbusMaster node;
+
+void preTransmission()
+{
+  digitalWrite(MAX485_RE_NEG, 1);
+  digitalWrite(MAX485_DE, 1);
+}
+
+void postTransmission()
+{
+  digitalWrite(MAX485_RE_NEG, 0);
+  digitalWrite(MAX485_DE, 0);
+}
+
+void setup()
+{
+  pinMode(MAX485_RE_NEG, OUTPUT);
+  pinMode(MAX485_DE, OUTPUT);
+  // Init in receive mode
+  digitalWrite(MAX485_RE_NEG, 0);
+  digitalWrite(MAX485_DE, 0);
+
+  // Modbus communication runs at 115200 baud
+  Serial.begin(115200);
+
+  // Modbus slave ID 1
+  node.begin(1, Serial);
+  // Callbacks allow us to configure the RS485 transceiver correctly
+  node.preTransmission(preTransmission);
+  node.postTransmission(postTransmission);
+}
+
+bool state = true;
+
+void loop()
+{
+  uint8_t result;
+  uint16_t data[6];
+
+  // Toggle the coil at address 0x0002 (Manual Load Control)
+  result = node.writeSingleCoil(0x0002, state);
+  state = !state;
+
+  // Read 16 registers starting at 0x3100)
+  result = node.readInputRegisters(0x3100, 16);
+  if (result == node.ku8MBSuccess)
+  {
+    Serial.print("Vbatt: ");
+    Serial.println(node.getResponseBuffer(0x04)/100.0f);
+    Serial.print("Vload: ");
+    Serial.println(node.getResponseBuffer(0xC0)/100.0f);
+    Serial.print("Pload: ");
+    Serial.println((node.getResponseBuffer(0x0D) +
+                    node.getResponseBuffer(0x0E) << 16)/100.0f);
+  }
+
+  delay(1000);
+}
+