What is this?

This is a GyroFlow-compatible data logger firmware for the esp32 and esp32-c3 microcontrollers (and probably others supported by esp-idf)

Required hardware

• An esp32 or esp32-c3 with 4MB flash
• A BMI270, BMI160 or MPU6050 IMU
• 4 wires

You can get these as separate modules or on a single board (EspLog)

Parameter docs

HERE

How to flash and get started with the DIY version?

YouYube tutorial

1. Connect your IMU board to the ESP board. For esp32 it is recommended to connect SDA and SCL to pins 16 and 17 accordingly. For esp32-c3 - to pins 6 and 7.
2. Download the firmware from github. You can find the latest build in "Artifacts" of the latest build from the "Actions" tab. The zip file will contain a readme file with a command line for flashing using esptool.
3. After flashing the firmware you should see a wifi network with SSID starting with "esplog_". Connect to that network with "12345678" password.
4. Go to http://192.168.4.1/settings, enter the SDA and SCL pin numbers you have connected the IMU to, click "Apply".
5. Reboot the board and go to http://192.168.4.1. If the IMU is OK, "Avg gyro sample int. (ns)" should be non-zero.
6. Calibrate the accelerometer. For that you need to go to http://192.168.4.1/calibration, add some calibration points (for example x-up, x-down, y-up, y-down, z-up, z-down). Hold your IMU stationary for some time before adding a points as the accelerometer data is low-pass filtered. Then click "Calculate offsets" and then "Save to flash".
7. You can connect a button and a led to any free pins and assign the pin numbers in settings. NOTE: when recording is started using the button, wifi is disabled until you stop the recording using the button. This is done intentionally.

Screenshots

Other resources

Test flight

Video about workflow

EspLog PCB (the oldest one, 4 layers, proper ceramic antenna)

Four-layer 11 x 14 mm PCB with esp32-c3, 3.3v ldo and either bmi160, bmi270 or lsm6dsr gyro. The side with the components can be submerged in epoxy, making the logger almost a perfect 11x14x2.5mm cube, so it is easier to glue to a camera.

EasyEDA project

Assembled:

2-layer PCB designs

There also are two alternative designs in this repository: https://github.com/VladimirP1/esplog-hardware

To open the project files, use KiCad 6

1. esplog_hv is a 2-layer deisgn with a built-in switching regulator supporting 4.5-30v input voltage range.
2. esplog_ldo is a 2-layer design, which is almost exacly the same as the older 4-layer design.

Both 2-layer designs omit the ceramic antenna(because it can be very hard to buy) and implement the antenna as a random piece of trace. Wifi TX power over 7dbm cannot be used (otherwise the signal gets distorted too much to be recieved).