We will need some Modbus tester : KMtronic_ModBus_Tester So mach3 will read from thees returned packetsĠ1 04 02 00 00 78 f0 returned ingormation is 0Īnd from 01 04 02 00 01 b9 30 returned ingormation is 1 ( but basicaly it is N*8bits of data in this case so 2 bit containing 00 00) 02 00 00 lets simplyfy this for the data information.04 is information that we are going to read input register.So thisway we can read state of inputpin on arduino. So we will send request from mach3 to read input register and arduino replyes with data containing 1 or 0. In real comunication these packets are modbus reply for '01 04 00 00 00 01 31 ca' question. The whole think is very simle, arduino recives in this case any 8 bites and replies with

This was the inspiration for my test and the code is from this page. i was trying it with some rs485 hardware. i just wanted to add it in case you wanted to know what the one i have looks like. On left side of image is the USB to rs485 adapter (you dont need that). Led should have resistor in series, i just coudnt be bothered and the led suvived. Arduino connected to PC + one led but you dont need the LED (it is just indicator so i know what information should be send back from arduino) and cable so you can ground a pin on arduino. In this case the standard Usb cable connecting pc and arduino will do.īut you can buy USB to rs485 adapter and connect to rx tx lines and it should be basicaly the same think.

The comunication of mach3 with arduino will be done using uart. Doesnt matter the amount of connections the hardware protocol uses, basicaly it boils down to one comunication line for half duplpex and two for full duplex. Modbus is software protocol not hardware, so you can use it not only ower rs232 or rs485 but also let say uart usart. But if this will work for you then adding full modbus library for proper comunications shouldnt be any problem. You will end up with ability of mach3 to read input pin on arduino. This will not use any modbus library it is just proof of working. I will describe here how to connect arduino directly to mach3 without any additional hardware.

Setup serial modbus mach3