07-23-2024, 12:26 AM
Hi Kincony,
I hope you are well.
I have recently purchased the KC868-A2 via AliExpress.
This is a great device with ethernet and RS485. It is a very fine unit. It joins my KC868-A4 and KC868-A8 in my systems.
This unit was purchased to interface with ModBus water meters at a remote site.
This has been progressing well until I had a problem making the RS485 work.
The board is KC868-A2-V2.4. I notice this is slightly different to the circuit diagram on the website which is made for V2.3. I am not sure if this is part of my problem as I might be testing incorrect pins?
My issue is I cannot see RS485 waveforms at the output.
In my fault finding I traced back and looked at the signal at several points:
1. P6 9H connector on the "A and B" points. No signal during transmit.
2. I checked the output of MAX13487ELSA (pin 6 and pin 7) to find no output during transmit.
3. The output of the ESP32 Pin 8 shows the ModBus command (Siglent Storage Oscilloscope).
4. I checked input of MAX13487ELSA (pin 4 to gnd) to see the RS485 signal coming from the ESP32 Pin 8. It is good level. The ESP32 is running latest version Tasmota 14.1.0 and the UI confirms that the ModBus signals are working (this I think means the code is correct).
I see that the Pin 2 and pin 3 of the MAX13487 are held high (measures 5.2V) and so the device should present data on the RS485 oututs Pin6 and 5. There is no signal at A &B on P6 during transmit.
Do you have anysuggestions as to what is happening?
I am doing something incorrect or is there possibly a fault?
Many thanks for any assistance you can provide.
Rgds
Adam
I hope you are well.
I have recently purchased the KC868-A2 via AliExpress.
This is a great device with ethernet and RS485. It is a very fine unit. It joins my KC868-A4 and KC868-A8 in my systems.
This unit was purchased to interface with ModBus water meters at a remote site.
This has been progressing well until I had a problem making the RS485 work.
The board is KC868-A2-V2.4. I notice this is slightly different to the circuit diagram on the website which is made for V2.3. I am not sure if this is part of my problem as I might be testing incorrect pins?
My issue is I cannot see RS485 waveforms at the output.
In my fault finding I traced back and looked at the signal at several points:
1. P6 9H connector on the "A and B" points. No signal during transmit.
2. I checked the output of MAX13487ELSA (pin 6 and pin 7) to find no output during transmit.
3. The output of the ESP32 Pin 8 shows the ModBus command (Siglent Storage Oscilloscope).
4. I checked input of MAX13487ELSA (pin 4 to gnd) to see the RS485 signal coming from the ESP32 Pin 8. It is good level. The ESP32 is running latest version Tasmota 14.1.0 and the UI confirms that the ModBus signals are working (this I think means the code is correct).
I see that the Pin 2 and pin 3 of the MAX13487 are held high (measures 5.2V) and so the device should present data on the RS485 oututs Pin6 and 5. There is no signal at A &B on P6 during transmit.
Do you have anysuggestions as to what is happening?
I am doing something incorrect or is there possibly a fault?
Many thanks for any assistance you can provide.
Rgds
Adam