MQTT auto-discovery/publish broken for analog sensors attached to GPIOs lower than 10

[gwilford]

Description

Attaching an analog sensor to GPIO 4 results in "unknown" values in HA

Steps to reproduce

Configure GPIO less than 10 (e.g. 4) as ADC in UI (no need to connect anything to the pin)
Check value of entity in HA - it will be "unknown"

Expected behaviour

The value in HA should be 0 (or the measured value)

The issue

Data from MQTT Explorer.
The MQTT auto-discovery config:

{
  "stat_t": "ems-esp/analogsensor_data",
  "val_tpl": "{{value_json['4'].value}}",
  "object_id": "analog_sensor_Garage ldr",
  "name": "Garage ldr",
  "uniq_id": "analogsensor_4",
  "unit_of_meas": "mV",
  "dev": { 
    "ids": ["ems-esp"]
  }
}

The MQTT publish:

{
  "04": {
    "name": "Garage ldr",
    "value": 60
  }
}

The config refers to 4 whereas the publish is for 04

This is due to use of the following function in helpers.cpp for the publish but not for the config

// for decimals 0 to 99, printed as a 2 char string
char * Helpers::smallitoa(char * result, const uint8_t value) {
    result[0] = ((value / 10) == 0) ? '0' : (value / 10) + '0';
    result[1] = (value % 10) + '0';
    result[2] = '\0';
    return result;
}

Formatting the publish on line 375 of analogsensor.cpp:

JsonObject dataSensor = doc.createNestedObject(Helpers::smallitoa(s, sensor.gpio()));

Formatting the config on line 403:

snprintf(str, sizeof(str), "{{value_json['%d'].value}}", sensor.gpio());

Using smallitoa() to format the config or removing it from the publish should fix this.

Firmware v3.4.4

[MichaelDvP]

Thanks for reporting.
I think changing all to "04" looks better in formatting, but breaks HA by changing also the uniq_id. So changing the publish to "4" is better. Do you agree?

[proddy]

agree. Thanks for the detailed breakdown @gwilford

[gwilford]

Using "04" does look better.

It would break existing uniq_id but only for configs using low GPIOs which I don't think are working anyway. However, changing the publish from "04" to "4" might break anyone who had manually configured an MQTT subscribe in HA...

[gwilford]

OK, just tested and can't seem to add a manual HA mqtt sensor with "0" prefix. This fails to parse:

mqtt:
  sensor:
    - name: "EMS-ESP GPIO4"
      state_topic: "ems-esp/analogsensor_data"
      value_template: "{{ value_json.04.value }}"

with Invalid config for [mqtt]: invalid template (TemplateSyntaxError: expected token 'end of print statement', got 'integer') for dictionary value @ data['mqtt']['sensor'][0]['value_template']. Got '{{ value_json.04.value }}'. (See ?, line ?).

whereas this parses just fine:

mqtt:
  sensor:
    - name: "EMS-ESP GPIO4"
      state_topic: "ems-esp/analogsensor_data"
      value_template: "{{ value_json.4.value }}"

In summary, I don't think changing the publish to "4" would break anyone who had tried to manually configure within HA and it may well be safer.

[MichaelDvP]

I think this should be {{ value_json.['04'].value }} to handle correctly. Or in code:
snprintf(str, sizeof(str), "{{value_json['%02d'].value}}", sensor.gpio());

[gwilford]

Sorry, spoke too soon. This does currently work if manually configured as below:

mqtt:
  sensor:
    - name: "EMS-ESP GPIO4"
      state_topic: "ems-esp/analogsensor_data"
      value_template: "{{ value_json['04'].value }}"

Either fix works for me though.

[proddy]

in dev-16