Modbus component 2021.5.1 error

[rostislav-palivoda]

The problem

What is version of Home Assistant Core has the issue?

2021.5.1

What was the last working version of Home Assistant Core?

2021.4.6

What type of installation are you running?

Home Assistant OS

Integration causing the issue

modbus

Link to integration documentation on our website

https://www.home-assistant.io/integrations/modbus/

Example YAML snippet

• name: modbus_mb10td_01
  slave: 7
  address: 0
  count: 10
  input_type: holding
  data_type: custom
  structure: ">10h"
  scan_interval: 15

Anything in the logs that might be useful for us?

A lot of exceptions after update:

Traceback (most recent call last):
File “/usr/local/lib/python3.8/concurrent/futures/thread.py”, line 57, in run
result = self.fn(*self.args, **self.kwargs)
File “/usr/src/homeassistant/homeassistant/components/modbus/sensor.py”, line 232, in
self.hass, lambda arg: self._update(), self._scan_interval
File “/usr/src/homeassistant/homeassistant/components/modbus/sensor.py”, line 300, in _update
registers = self._swap_registers(result.registers)
AttributeError: ‘ModbusIOException’ object has no attribute ‘registers’

Additional information

Caused by https://github.com/home-assistant/core/blame/cbf46328955ef62560295471159414242f8c203c/homeassistant/components/modbus/sensor.py#L298

[probot-home-assistant]

modbus documentation
modbus source
_{^{(message by IssueLinks)}}

[rostislav-palivoda]

- name: modbus_mb10td_01
  slave: 7
  address: 0
  count: 10
  input_type: holding
  data_type: custom
  structure: ">10h"
  scan_interval: 15

[rostislav-palivoda]

https://github.com/home-assistant/core/blame/cbf46328955ef62560295471159414242f8c203c/homeassistant/components/modbus/sensor.py#L298

[rostislav-palivoda]

I think backward compatibility is broken in 2021.5 and I can not upgrade. If this is the case, then please return ability to request values in bulk - data_type: custom.

Single request per value will not work, i.e. some devices has hundreds of values and in 4.6 it was possible to read all of them in a single request. Single value request approach brings RS485 network to its limits very fast - each request is multiplied by 1) values per device; 2) amount of devices in a network; and limited by 1) baud rate restrictions VS length of the lines 2) frequency of requests in the RS485 network.

[janiversen]

You can still do multi request with "struct:" the limitation is (as it was in 2021.4.6) 255 bytes in the result string. We did not touch that (as far as I know).

[rostislav-palivoda]

I've got this error right after migration from 4.6 to 5.1. If mentioned config does not cause described error you can close the ticket.

[janiversen]

The error have nothing to do with your configuration that looks ok.

closing.