Read Serial (RS485) Data

[admin]

yes, install serial node

[v1rtus]

NODE-RED sees the /dev/ttyS0 and even connects to it, but every command send fail.

I changed Ubuntu Core to Raspberry Pi OS Lite and still same issue.

I have another KC868-Server, so I will try if there is the same problem.

[admin]

ok, you can try to use another.

[v1rtus]

I tried with another KC868-Server and unfortunately the behavior is the same

Steps that I did:

1. Installed Raspbian Lite
   
2. Installed Docker
   
3. Installed Portainer
   
4. Permissions for /dev/ttyS0 - sudo chmod 666 /dev/ttyS0
   
5. Deployed Node-RED container
   
6. Installed modbus module
   
7. Did configure modbus Read node and deployed it
   

The node is connected to the serial but when I try to read data from it it returns error - Modbus Failure On State sending Get More About It By Logging

   

I connect CM4 RS485 port to relay port as it is shown in video and try to read relay statuses.

Update:

After I switch to USB-RS485 adapter everything works fine.

[admin]

i think you can install Installed Raspbian full version.
if have installed Installed Raspbian OS and home assistant all are no problem, just need to enable serial port on CM4. I think it's OS system file setting problem.
i have tested "Raspberry Pi OS with desktop" OS, download link: https://downloads.raspberrypi.org/raspio...m64.img.xz

[v1rtus]

I installed the full Raspbian OS x64 (with desktop) and still cannot read data using integrated RS485 port (the error is same)

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I installed NODE-RED locally (without docker) and the results are same.

• /dev/ttyUSB0 - modbus is working fine
  
• /dev/ttyS0 - error: Modbus Failure On State sending Get More About It By Logging
  

[admin]

there is information about this in node-red forum: https://discourse.nodered.org/t/modbus-f...ng/53942/8
i suggest you use "serial" node to test firstly, not need "modbus" node test firstly. so that can confirm whether hardware serial is enabled.

[v1rtus]

   

The serial port is connected, could u please send me a command that I can use for testing. For example read relays statuses or turn on/off single relay.

[admin]

if you have USB-RS485 adapter. you can let KC868-Server's RS485 connect to your USB-RS485, let your USB-RS485 connect with a PC, use "serial debug tool" to see whether have received message from KC868-Server.

[v1rtus]

Never done that before, could u please provide some tutorial?

Could u please provide me some guidelines how to check RS485 port, otherwise looks like the both modules that I have are with defect

If the issue is somewhere with NODE-RED I need to make sure that serialport is working and then I can start looking for some solution.