[ModBus RTU communication between Omron CP1E (CP1W-CIF11) and an Arduino using MAX485 RS485 transceiver]

Hello everyone!

Briefly introduction, I would like to communicate and test the following hardwares:

1- Omron CP1E (using an Option Port CP1W-CIF11) ; and

2- Arduino Nano using MAX485 RS485 transceiver.

The CP1E will operate in "Modbus-RTU simple master" as illustrated in image 01. The arduino will be in slave mode address 1 and the library used is "SimpleModbus NG" ( https://github.com/angeloc/simplemodbusng/tree/master/SimpleModbusSlave ).

Taking the sample in official manual ( https://industrial.omron.eu/en/services-support/technical-tools/downloads#cp1e ) , pages 248-253 in the "CP1E CPU Unit Software User's Manual" (Image 04) describes a sample communication to an "Inverter Slave".

I want to use the Arduino Slave as the Inverter Slave just to be sure that all previous steps are correct.

Therefore, I would like to know:

1- As illustrated in Image 02, Am I missing any resistors?

2- Should I connect the GND to the FG?

3- In this scenario, the DIP switch setup should be as illustrated in image 03? Only DIP4 is OFF.

4- Can I test it just forcing A641.00 and checking the DM Area Data, as shown in Image 05?

The code used in it is the following:

// Wiring: Arduino and MAX485
// RX0 - RO
// TX1 - DI
// D2  - DE/RE

#include "SimpleModbusSlave.h"

enum {
	REGISTER_0,
	REGISTER_1,
	REGISTER_2,
	REGISTER_3,
	REGISTER_4,
	REGISTER_5,
	REGISTER_6,
	REGISTER_7,
	REGISTER_8,
	TOTAL_REGS_SIZE
};

unsigned int holdingRegs[TOTAL_REGS_SIZE] = { 0, 1, 2, 3, 4, 5, 6, 7, 8 };

void setup() {
	modbus_configure(&Serial, 9600, SERIAL_8N1, 1, 2, TOTAL_REGS_SIZE, holdingRegs);
}

void loop() {
	modbus_update();
}

 

Any answer can be helpful. Thank you for your time!

 

Regards,

Jose.