modbus slave works, second adc added

SimpleModbusSlave.h

@@ -0,0 +1,63 @@
+#ifndef SIMPLE_MODBUS_SLAVE_H
+#define SIMPLE_MODBUS_SLAVE_H
+
+// SimpleModbusSlaveV7
+
+/*
+ SimpleModbusSlave allows you to communicate
+ to any slave using the Modbus RTU protocol.
+ 
+ This implementation DOES NOT fully comply with the Modbus specifications.
+ 
+ Specifically the frame time out have not been implemented according
+ to Modbus standards. The code does however combine the check for
+ inter character time out and frame time out by incorporating a maximum
+ time out allowable when reading from the message stream.
+ 
+ SimpleModbusSlave implements an unsigned int return value on a call to modbus_update().
+ This value is the total error count since the slave started. It's useful for fault finding.
+ 
+ This code is for a Modbus slave implementing functions 3 and 16
+ function 3: Reads the binary contents of holding registers (4X references)
+ function 16: Presets values into a sequence of holding registers (4X references)
+ 
+ All the functions share the same register array.
+ 
+ Note:  
+ The Arduino serial ring buffer is 128 bytes or 64 registers.
+ Most of the time you will connect the arduino to a master via serial
+ using a MAX485 or similar.
+ 
+ In a function 3 request the master will attempt to read from your
+ slave and since 5 bytes is already used for ID, FUNCTION, NO OF BYTES
+ and two BYTES CRC the master can only request 122 bytes or 61 registers.
+ 
+ In a function 16 request the master will attempt to write to your 
+ slave and since a 9 bytes is already used for ID, FUNCTION, ADDRESS, 
+ NO OF REGISTERS, NO OF BYTES and two BYTES CRC the master can only write
+ 118 bytes or 59 registers.
+ 
+ Using a USB to Serial converter the maximum bytes you can send is 
+ limited to its internal buffer which differs between manufactures. 
+ 
+ The functions included here have been derived from the 
+ Modbus Specifications and Implementation Guides
+ 
+ http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
+ http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b.pdf
+ http://www.modbus.org/docs/PI_MBUS_300.pdf
+*/
+
+#include "Arduino.h"
+
+// function definitions
+unsigned int modbus_update();
+void modbus_configure(HardwareSerial *SerialPort,
+											long baud,
+											unsigned char byteFormat,
+											unsigned char _slaveID, 
+                      unsigned char _TxEnablePin, 
+                      unsigned int _holdingRegsSize,
+                      unsigned int* _regs);
+
+#endif