Display MQTT JSON value on matrix LED max7219

ESPHome
1

Hi,

I try with no success to display on a matrix LED max7219 a JSON value from a MQTT topic.
My message is displayed in the logs. But I can’t display a part of this JSON message on my LED matrix.

The full JSON is displayed but I just want the value of PAPP : 400
My json looks like : ‘{“PAPP”:400,“IMAX1”:90}’

I try with lambda or text _sensor …

text_sensor:
  - platform: mqtt_subscribe
    name: "Data from topic"
    id: elec_value
    topic: my/topic
 
spi:
  clk_pin: 27
  mosi_pin: 26

display:
  - platform: max7219digit
    cs_pin: 14
    num_chips: 4
    intensity: 15
    lambda: |-
      if (id(mqtt_client).is_connected()) {
        it.printf(0, 4, id(digit_font), TextAlign::CENTER_LEFT, id(elec_value).state.c_str());
      }

Have you an idea ? thanks

2

Start simple, can you display anything on the display?

3

Like I said : The full JSON is displayed: ‘{“PAPP”:400,“IMAX1”:90}’
but I just want display the value of PAPP : 400
I try with on_json_message and subscribe_json but I think I don’t have the good synthaxe

4

Sorry I probably read too quickly. My JSON is crap, but this site may help Best JSON Parser Online [2022]

5

No problem for the Quick read.
But I don’t understand your answer.
I don’t need a online parser.
I need to parse the JSON message and the value of the PAPP key in the display block

Thanks

6

The online site can help you visualise your JSON data. That’s all. Mind you, yours is simple enough.

Looking at it I probably meant to point you here, sorry for the confusion. https://jsonpathfinder.com/

The path you are looking for is x.PAPP so (I think) something like the example for on_json_message. MQTT Client Component — ESPHome

7

How about if you create a sensor in HA, which contains the PAPP and then just display the sensors value in ESPHome?

sensor.yaml:

- platform: mqtt
  state_topic: 'my/topic'
  name: 'Data from topic'
  value_template: "{{ value_json.PAPP }}"

ESPHome:

text_sensor:
  - platform: homeassistant
    id: papp
    entity_id: sensor.data_from_topic
display:
  - platform: max7219digit
    cs_pin: 14
    num_chips: 4
    intensity: 15
    lambda:|-
      it.printf(0, 4, id(digit_font), TextAlign::CENTER_LEFT, id(papp).state.c_str());
2 Likes
8

Thanks !
I will try this.