Thanks for the help I am making some progress. I have got the slave communicating with a master using the SimpleSlaveModbus example. When I try to use the code from the Android/Arduino project there is an error on line 34. I have tried to find the problem from the reference but no solution as yet.

sketch_feb09a.ino: In function 'void setup()':
sketch_feb09a:34: error: expected `;' before 'pinMode'
sketch_feb09a:34: error: expected `)' before ';' token
sketch_feb09a.ino: At global scope:
sketch_feb09a:38: error: expected constructor, destructor, or type conversion before '(' token
sketch_feb09a:39: error: expected constructor, destructor, or type conversion before '(' token
sketch_feb09a:40: error: expected constructor, destructor, or type conversion before '(' token
sketch_feb09a:41: error: expected constructor, destructor, or type conversion before '(' token
sketch_feb09a:44: error: expected constructor, destructor, or type conversion before '(' token
sketch_feb09a:47: error: expected constructor, destructor, or type conversion before '(' token
sketch_feb09a:50: error: expected unqualified-id before 'for'
sketch_feb09a:50: error: expected constructor, destructor, or type conversion before '<' token
sketch_feb09a:50: error: expected constructor, destructor, or type conversion before '++' token
sketch_feb09a:53: error: expected declaration before '}' token

Thanks for the information the project looks great

I have tried to compile your code and the original SImpleModbusSlave example and both give the same error

SimpleModbusSlaveExample.ino: In function 'void setup()':
SimpleModbusSlaveExample:85: error: 'modbus_configure' was not declared in this scope
SimpleModbusSlaveExample.ino: In function 'void loop()':
SimpleModbusSlaveExample:95: error: 'modbus_update' was not declared in this scope

There is some information that this is related to the version of Arduino and I ahve compiled in 1.01 and the error is the same

Any ideas?

I am starting a project to build a Modbus RTU slave using a MAX485 and an UNO. I have seen all the projects available on the web but all seem to be outdated. Any information or code to get started would be appreciated