ESPHome Ultrasonic sensor SR04T via UART

ESPHome
21

I received the same sensor (AJ-SR04M) and I can’t get it to work. It shows no distance readings. I have been following this thread but to no avail. Can someone enlighten me where to put the AJ_SR04M_Sensor.h file. I was hoping to use it withou any resistor (to work just like the HC-SR04). Are there any changes to the code?

22

Hello - I found this post interesting - I’m starting to connect AJ-SR04M to my HA via esphome board : esp32 or wemos D1 mini

Have You considered voltages ?

I assume that You get 5v for AJ-SR04M from the board (esp32 or D1mini) but as far as I know TX/RX pins on these boards are working with 3.3v.
So If You connect TX/RX from SR04M You get 5v signal … and connecting it to 3.3v pins can cause damage or malfunction.
There is an instruction how to connect and there is a film presenting it is working but this example is based on Arduino UNO - there are 5v pin !
instructions
film - arduino UNO working with AJ-SR04M

So … did You noticed this “voltage question” ?

23

Hello everyone,
I am trying to reproduce this configuration on my Home Assistant via ESPHOME.
However, I have errors, and I’m more than new to Arduino.

My setup is a “Wemos D1 mini” with “JSN-SR04T” (AJ-SR04M) and 47KΩ residence on R19

In /homeassistant/esphome/
Here is my file AJ_SR04M_Sensor.h

#include "esphome.h"
 
class AJ_SR04M_Sensor : public PollingComponent, public UARTDevice, public Sensor {
 public:

  AJ_SR04M_Sensor(UARTComponent *parent) : PollingComponent(5000), UARTDevice(parent) {}

// AJ_SR04M_Sensor format:
// Trigger: 0x00
// Response: Byte1          Byte2  Byte3  Byte4               Byte5
//           Start Byte=FF  MSB    LSB    Checksum (LSB+MSB)  00

  void update() override {
  
    char frame[5];
    int pos = 0;


    float value = 0.0;

    write(0x01);
    while (available()) {


      frame[pos] = read();
      pos++;
      if(pos==5) {
        if ((frame[0] == 0xFF) && (frame[4] == 0x00) && ((frame[1]+frame[2])==frame[3])) {
          value = ((frame[1]<<8) + frame[2]) / 10.0;
          publish_state(value);
        }
        break;
      }
    }
  }
};

and my esp-cuve.yaml file

esphome:
  name: esp-cuve
  friendly_name: esp-cuve
  includes:
    - AJ_SR04M_Sensor.h

uart:
  id: uart_bus
  tx_pin: D1
  rx_pin: D2
  baud_rate: 9600
  stop_bits: 1
  rx_buffer_size: 4
  debug:

esp8266:
  board: d1_mini

# Enable logging
logger:
  baud_rate: 0

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

captive_portal:

web_server:
  port: 80

# Time: https://esphome.io/components/time.html
time:
  - platform: homeassistant
    timezone: "Europe/Paris"
    id: homeassistant_time

# Status Binary Sensor: https://esphome.io/components/binary_sensor/status.html
binary_sensor:
  - platform: status
    name: "Status"

# Restart Button: https://esphome.io/components/button/restart.html
button:
  - platform: restart
    name: "Restart"


sensor:

  - platform: custom
    lambda: |-
      auto my_sensor = new AJ_SR04M_Sensor(id(uart_bus));
      App.register_component(my_sensor);
      return {my_sensor};
    sensors:
     unit_of_measurement: cm
     accuracy_decimals: 1
     name: "Distance"

No error on compilation but here are the logs

[20:21:22][D][uart_debug:114]: >>> 01
[20:21:27][D][uart_debug:114]: >>> 01
[20:21:32][D][uart_debug:114]: >>> 01
[20:21:37][D][uart_debug:114]: >>> 01
[20:21:42][D][uart_debug:114]: >>> 01

Do you have any idea where the problem could come from?
Thank you again for your help

24

Just curious, did you get it working? I’m in the same situation.

25

Did you figure this one out? I’m very new to esphome so I’m really just trying anything an everything, but I’ve just got it working by removing the checksum comparison.

Wish I could say why that would be causing errors for me, but its the only way I’m getting any readings, and have been consistent and very accurate.

26

I’m having issues getting this working - see