ESP32 Pressure Sensor Firmware

Purpose

This project provides firmware for an ESP32-based pressure sensor system using the DFRobot SEN0257 pressure sensor. The firmware is designed to read pressure data from the sensor and support integration with smart home platforms.

Features

• WiFi Connectivity: Supports connecting to WiFi for remote monitoring.
• MQTT Support: Publishes sensor data via MQTT for integration with various platforms.
• Home Assistant Integration: Automatically detects and configures the sensor in Home Assistant.
• Web Interface: Provides a web-based user interface for configuration and monitoring.
• Zigbee (Experimental): Zigbee functionality is present but currently disabled by default.

Prerequisites

To get started, you will need:

• Hardware:
  • ESP32-C6 or ESP32-S3 microcontroller (both have been tested).
  • DFRobot SEN0257 pressure sensor.
• Software:
  • ESP-IDF framework (version 4.4 or higher recommended).

Wiring

The following wiring schema is expected by default:

+------------+-----------+
| Sensor Pin | ESP32 Pin |
+------------+-----------+
| GND        | GND       |
+------------+-----------+
| VCC        | +5V       |
+------------+-----------+
| Signal     | IO03      |
+------------+-----------+

It is very recommended to connect a 0.1uF ceramic capacitor between GND and IO03 to act as the filter and suppress voltage spikes and drops.

You may consider the other IO pin so you can change PRESSURE_SENSOR_PIN in file sensor.h. But keep in mind that not all ESP32 variants have ADC feature enabled and it may differ between ESP32 variants.

Building and Flashing

1. Setup the ESP-IDF Environment:
   • Follow the official ESP-IDF setup guide to configure your development environment.
   • Further on we will assume, that you're using Unix-based OS (Linux, macos) and you've installed ESP-IDF into $HOME/esp-idf folder.
2. Clone this Repository:

   git clone https://github.com/rpavlyuk/ESPPressureSensor
   cd ESPPressureSensor

3. Initiate ESP-IDF: This will map the source folder to ESP-IDF framework and will enable all needed global variables.

   . $HOME/esp-idf/export.sh

4. Build the firmware:

   idf.py build

   You will get idf.py: command not found if you didn't initiate ESP-IDF in the previous step. You may also get build errors if you've selected other board type then ESP32-C6 or ESP32-S3.
5. Determine the port: A connected ESP32 device is opening USB-2-Serial interface, which your system might see as /dev/tty.usbmodem1101 (macos example) or /dev/ttyUSB0 (Linux example). Use ls -al /dev command to see the exact one.
6. Flash the Firmware:

   idf.py -p /dev/ttyUSB0 flash monitor

   Replace /dev/ttyUSB0 with the appropriate port for your system.

Note

Every time you change the board type (e.g., from ESP32-C6 to ESP32-S3, the framework is re-creating sdkconfig file which makes some very important settings gone. Thus, you (might) need to change/set some settings if you've changed the device board:

• Open SDK settings menu by running:

  idf.py menuconfig

• Set the following parameters:
  • Partition table -> Custom partition table CSV as the option
  • Partition table -> Custom partition CSV file set to partition_table/partition.csv
  • Serial flasher config -> Flash size to 4Mb or 8Mb
  • Serial flasher config -> Detect flash size when flashing bootloader to enabled
  • Component config -> HTTP Server -> Max HTTP Request Header Length to 8192
  • Component config → ESP System Settings -> Event loop task stack size to 4096
  • Component config → ESP System Settings -> Main task stack size to 4096
  • Component config → ESP System Settings -> Minimal allowed size for shared stack to 2048

Initiation

WiFi Setup

• On the first boot, the device will start in access point mode with the SSID PROV_AP_XXXXXX. The exact named will be different depending on the device hardware ID (which is built in). The password is SSID name plus 1234. For example, PROV_AP_XXXXXX1234
• Use the ESP SoftAP Prov (iOS, Android) mobile app to connect to the device and configure WiFi settings. Read more here if you want to know more about the SoftAP provisioning.

Device Setup

• Device will initiate itself with default settings once the WiFi was provisioned. All further configuration, including sensor calibration, will/can be made via WEB interface.

Note

Currently only DHCP mode is supported.

WEB Setup

• Device starts the WEB interfance available as http://<WIFI-IP>/.
• You can start seeing the pressure readings by visiting Status page.
• Basic configuration parameters on Configuration page:
  • MQTT Mode: defines how MQTT works
    • Disabled: MQTT is disabled
    • Connect Once: MQTT is enabled. Connection will be established, but no reconnect attempts will be made once it is dropped.
    • Auto-Connect: MQTT is enabled. Connection will operate in keep-alive mode, reconnecting on failures.
  • MQTT Server, MQTT Port, MQTT Protocol, MQTT User, MQTT Password: MQTT connection string parameters. Protocol mqtts is supported but CA/root certificate management UI has not been implemented yet.
  • MQTT Prefix: top level path in the MQTT tree. The path will look like: <MQTT_prefix>/<device_id>/...
  • HomeAssistant Device integration MQTT Prefix: HomeAssistant MQTT device auto-discovery prefix. Usually, it is set to homeassistant
  • HomeAssistant Device update interval (ms): how often to update device definitions at HomeAssistant.
• Sensor parameters:
  • Sensing interval (ms): how often to read the data from sensor
  • Sensor ADC Offset (V): calibration parameter. It represents which voltage corresponds to a zero pressure. We will explain calibration in separate section.
  • Sensor Linear Multiplier: this is a linear multiplier (dependency) between voltage in Volts and pressure in Pascals. No need to change it unless you know why.
  • Number of samples to collect per measurement, Interval between samples (ms), Threshold for samples filtering (%): these are advanced measurement sampling parameters. The device implements smart measurement when collects N samples of voltage (ADC) per one measurement with certain small interval, calculates the mediane and drops all other then deviate from median by certain threshold.

Calibration

1. Connect the pressure sensor to ESP32 device and leave it open. Means, do not mount it into the tank or pipe.
2. Go to the WEB interface, open Status page and note the Voltage value. For example, it can something like 0.489 V
3. Go to the Config tab, set this value as Sensor ADC Offset (V) parameter and reboot the device.

You may into more advanced mode and do more precise calibration if you analon pressure manometer. In this case you may adjust also Sensor Linear Multiplier.

Home Assistant Integration

The device will automatically enable itself in Home Assistant if:

• both HA and the device are connected to the same MQTT server
• HomeAssistant Device integration MQTT Prefix is set correctly
• auto-discovery is enable in Home Assistant (should be enabled by default)

WEB API

The device is exposing a simple read-only API URL to get the device status and sensor data.

http://<WIFI-IP>/status-data

Known issues, problems and TODOs:

• CA certification configuration for SSL (mqtts) mode to be implemented
• Static IP support needed
• Device may have memory leaks when used very intensively (to be improved)

License and Credits

• GPLv3 -- you're free to use and modify the code
• Uses ESP32_NVS library by VPavlusha
• Consider putting a star if you like the project
• Find me at roman.pavlyuk@gmail.com