RS486 and MODBUS RTU

[r_merc]

I am trying to run the Example Code and am not getting the slave Controllino Maxi Pure to respond to the master Maxi Pure. I can’t figure out what I am doing wrong.

[r_merc]

I was reading and I came across this. So are they talking about modifying Modbus.h?

“Modbus Master-Slave library for Arduino (ModbusRtu.h) was taken from the website: https://github.com/smarmengol/Modbus-Master-Slave-for-Arduino

It was necessary to modify setting of the PORTJ for pins DE and RE control. These pins are located at the PORTJ and on the pins PIN6(DE) and PIN5(RE).”

[r_merc]

I added some troubleshooting lines to the slave code and discovered that when the line

ControllinoModbusSlave.poll(ModbusSlaveRegisters, ;

is called that the controllino resets and starts the sketch again. Sometimes it will run through the loop 2,3 or 4 times and then start over.

Anyone have any ideas why that would be happening?

[r_merc]

OK here is a new twist on this. If I remove all the digitalWrite() form the sketch I can get the Mast and slave to communicate. With the digitalWrite in the Slave the communications fails. Any Ideas?

[gmartinez]

Hi,

I Had the same problem, I tried to use ControllinoModbusSlave, and others libraries, without luck, I check the Controllino.h and found this two functions:

void Controllino_RS485TxEnable( void );

void Controllino_RS485RxEnable( void );

the question is, can I use thos funcitions to enable RS485 data transfer?

[Lukas]

Hello r_merc – sorry for the late reply. Have you resolved the issue, please? It seems to me that one of the outputs was connected to ground and then the digitalWrite() caused short circuit and device reset.

Hello gmartinez – yes, these API is for the RS485 direction control. Please see our latest RS485 example here.