Modbus direction control
Posted: Sun Jul 24, 2022 10:15 pm
Hi,
I thought it best to start a new topic so I don't clutter the other one up.
I have been having a lot of issues with Modbus RS485, I am getting closer but now think there is an issue with the direction control.
I now have the send message as it should be but I get no response from the slave. Instead of the device I hooked up a USB/RS485 converter and Modbus slave software. This showed it was only getting part of the message, the logic analyser showed it was sending it all but it looks like the data direction is being changed early. I put the link for the direction to VCC so it was high permanently and the slave receives the whole message which leads me to believe there is an issue with the direction software.
Here is the slave showing part message. Here is the logic analyser showing the whole message being sent but the direction changes after the function byte. Here is the slave showing the whole message received and a simulated response. The project is here if you need it, 2nd to last post. viewtopic.php?f=3&t=1348
Regards,
Bob
I thought it best to start a new topic so I don't clutter the other one up.
I have been having a lot of issues with Modbus RS485, I am getting closer but now think there is an issue with the direction control.
I now have the send message as it should be but I get no response from the slave. Instead of the device I hooked up a USB/RS485 converter and Modbus slave software. This showed it was only getting part of the message, the logic analyser showed it was sending it all but it looks like the data direction is being changed early. I put the link for the direction to VCC so it was high permanently and the slave receives the whole message which leads me to believe there is an issue with the direction software.
Here is the slave showing part message. Here is the logic analyser showing the whole message being sent but the direction changes after the function byte. Here is the slave showing the whole message received and a simulated response. The project is here if you need it, 2nd to last post. viewtopic.php?f=3&t=1348
Regards,
Bob