Modbus not working on PIC24FJ512GA606.

[seokgi]

Hello?
Modbus not working on PIC24FJ512GA606.
Doesn't work after update. The same program works fine on PIC18F45K40.
Help me Please.

Thank you.

[seokgi]

The program inside that works with Mobus Incoming works.

[BenR]

Hello,

Plase can you post your project file. Also have you done a one second flasher test to confirm the device is running at the rate you think it is.

[seokgi]

Uart is well.

[seokgi]

It still doesn't work well.
Please take a look again
Thank you.

[seokgi]

If I take the MAX485 chip off the PIC18F45K40 which works fine and put it on the PIC24FJ512GA606 board it doesn't work. Again, if I take the MAX485 chip off the PIC24FJ512GA606 and attach it to the PIC18f45K40, it works fine.

[BenR]

Is the voltage difference having an effect? does the Max chip work at 3v3?

Do you have anything you can use to look at the signals either side of the max chip, this is a useful low cost analyser if you don't currently have anything.

https://www.amazon.co.uk/gp/product/B08 ... XLJG&psc=1

[RGV250]

Hi,
When I was developing my Modbus on ESP32 I used one of these https://www.ebay.co.uk/itm/195143159538 ... L7EALw_wcB
and the Modbus master / slave from here https://www.simplymodbus.ca/RTUmaster.htm

Bob

[seokgi]

Thank you.

I have the equipment you mentioned.
I tested it with an oscilloscope and the equipment you mentioned.
I tested both 3.3v and 5v voltages.
I tested two chips, MAX485 and MAX13487.
And the software used MODBUS POLL.

BUS Type RS-232 works fine.
But RS-485 doesn't work.

Thank you for your interest.

[BenR]

Hello,

Are you powering the MAX485 IC from a 5V source, looking at the datasheet it needs 5V for RS485 to function correctly.