IMU (MPU6886) ESP-IDF

=====================

Small ESP-IDF project that reads an MPU6886 IMU over I2C and publishes readings over MQTT. Includes an option to run WiFi in STA (client) or AP (access point) mode.

Features

I2C communication functions for MPU6886 (accelerometer, gyro, temp)
MQTT client using esp-mqtt
WiFi: STA or AP mode selectable at build time
AP mode defaults to static IP 192.168.10.1/24 (configurable in code)
MQTT, Serial toggle using the boot button on the esp32

Quick start

Prerequisites

ESP-IDF installed and activated (the repo was developed with ESP-IDF v5.x).
Toolchain and Python deps per ESP-IDF instructions.

Build and flash

From the IMU root:

# configure project options
idf.py menuconfig

# build
idf.py build

# flash and monitor (set your serial port)
idf.py -p /dev/ttyUSB0 flash monitor

Project Configuration (menuconfig)

Open idf.py menuconfig and there you will see the ESP32 IMU Project Configuration submenu where you can configure specific data for I2C, MQTT and WIFI

I2C

In the I2C Master configuration submenu there are three options:

SCL GPIO Num - Default 21 - GPIO used for I2C SDA
SDA GPIO Num - Default 22 - GPIO used for I2C SCL
Master Frequency - Default 100000hz - I2C bus speed

MQTT

Broker URI - Default: "mqtt://192.168.4.2:1883"
MQTT Topic - Default: "esp32/imu"

WiFi / network

Toggle AP mode at build time by enabling CONFIG_WIFI_AP_MODE in menuconfig. If enabled the firmware will start as an access point on boot; if disabled the device starts as a station and attempts to connect to the configured SSID using the set Password
Toggle AP mode swaps the available settings when toggled between AP conf- and station configurations respectively
AP credentials can be set with WiFi AP SSID and Wifi AP Password.
Station credentials can be set with WiFi SSID and WiFi Password.

AP IP / DHCP

The AP is configured by default to use a static IP of 192.168.4.1 with netmask 255.255.255.0 and a DHCP server is started so clients receive addresses on that subnet.

Notes about units and macros

The macro SF_RAD_S (in main/mpu6886.h) is the degrees-to-radians conversion factor: PI/180. Gyroscope readings are converted from degrees/sec to radians/sec using this scale.
Sensitivity scale constants (e.g. ACCEL_SO_2G, GYRO_SO_250DPS) are used to convert raw sensor counts to physical units.

Troubleshooting

"MQTT_TOPIC undefined" at build time: run menuconfig
"I2C init failed": confirm SDA/SCL pins in menuconfig or wiring.

Files of interest

main/mpu6886.c - main application, WiFi init, MQTT publish loop
main/mpu6886.h - sensor constants and types

2.7 KiB Raw Blame History