Thousands of modbus_read_errors (one per second)

[kalwados]

HeidelBridge 3.4.0 now runs for a few week (switching from wbec). But I get a lot of modbus_read_errors: More than 500 error in 9 minutes; while modus_write_errors is very low (6). I've never had this large errror values with wbec; the hardware has not changed: Same Wallbox; same cable; but using ESP32 with RS485 converter instead of the old ESP8266. Any ideas how to analyze this problem? How can I find which command causes this error?
TIA,
Achim

[BorisBrock]

Mine has been running for over a month since the last update and has zero errors:

So something must be wrong with your hardware.
Are you sure

• The termination is correct? (120 Ohm at each end)
• The GND of the Modbus and ESP32 are correctly connected? (common ground)

[kalwados]

Hello Boris,

The termination is correct? (120 Ohm at each end)

I believe the MAX485 board already has a 120 Ohm terminator; but I'll check that.

The GND of the Modbus and ESP32 are correctly connected? (common ground)

No, just 2 wires A and B to the wallbox. Since I use a CAT7 cable for this, I will connect the shild to ESP32 ground. I will check the wiring at the weekend.

Achim

[kalwados]

The MAX485 board already has a 120 Ohm terminator on-board. The CAT7-Cable shield is tied to the Heidelberg wallbox ground. A and B wire are connected to the "IN" side connectors. S6/2 is ON for the on-board 120 Ohm terminator. On the ESP side, only A and B are connected to the MAX485 board. So the cable shield is grounded on one side.
Next, I'll connect my old laptop running putty to see the error logging output.

[kalwados]

Next, I'll connect my old laptop running putty to see the error logging output.

Now this is strange:
If I connect my laptop and using the USB port for powering the ESP32-Board; all errors are gone. Using "putty" I see the logging output; everything is fine. But when using an external power supply like the Raspberry Pi power supply (5,1 Volt, 3 Amp), the modbus_read_errors increases every 2 seconds.
Tried a different ESP32 board from different manufacturer): Still modbus_read_errors counting up.

First board is an ESP32 DevKit C4 from AZ-Delivery with USB-Micro port.
2nd board is an ESP32-WROOM32 from Amazon with USB-C port.

Any ideas?

[BorisBrock]

Sounds like a grounding issue. I would probably try to connect ESP32 ground to MAX485 ground, and then both to the shielding (wallbox ground).

[kalwados]

Sounds like a grounding issue. I would probably try to connect ESP32 ground to MAX485 ground, and then both to the shielding (wallbox ground).

That was it! Many thanks for this tip. I've connected the cable shield to the MAX485 GND pin. There are no more Modbus read/write errors.