SlimeVR Tracker firmware for ESP

Firmware for ESP8266 / ESP32 microcontrollers and different IMU sensors to use them as a vive-like trackers in VR.

Requires SlimeVR Server to work with SteamVR and resolve pose. Should be compatible with owoTrack, but is not guaranteed.

Configuration

Firmware configuration is located in the defines.h file. For more information on how to configure your firmware, refer to the Configuring the firmware project section of SlimeVR documentation.

Compatibility

The following IMUs and their corresponding IMU values are supported by the firmware:

• BNO085 & BNO086 (IMU_BNO085)
  • Using any fusion in internal DMP. Best results with ARVR Stabilized Game Rotation Vector or ARVR Stabilized Rotation Vector if in good magnetic environment.
• BNO080 (IMU_BNO080)
  • Using any fusion in internal DMP. Doesn't have BNO085's ARVR stabilization, but still gives good results.
• MPU-6500 (IMU_MPU6500) & MPU-6050 (IMU_MPU6050)
  • Using internal DMP to fuse Gyroscope and Accelerometer. Can drift substantially.
  • NOTE: Currently the MPU will auto calibrate when powered on. You must place it on the ground and DO NOT move it until calibration is complete (for a few seconds). LED on the ESP will blink 5 times after calibration is over.
• BNO055 (IMU_BNO055)
  • Performs much worse than BNO080, despite having the same hardware. Not recommended for use.
• MPU-9250 (IMU_MPU9250)
  • Using Mahony sensor fusion of Gyroscope, Magnetometer and Accelerometer, requires good magnetic environment.
  • See Sensor calibration below for info on calibrating this sensor.
  • Specify IMU_MPU6500 in your defines.h to use without magnetometer in 6DoF mode.
  • Experimental support!
• BMI160 (IMU_BMI160)
  • Using sensor fusion of Gyroscope and Accelerometer.
  • See Sensor calibration below for info on calibrating this sensor.
  • Calibration file format is unstable and may not be able to load using newer firmware versions.
  • Experimental support!
  • Support for the following magnetometers is implemented (even more experimental): HMC5883L, QMC5883L.
• ICM-20948 (IMU_ICM20948)
  • Using fusion in internal DMP for 6Dof or 9DoF, 9DoF mode requires good magnetic environment.
  • Comment out USE_6DOF in debug.h for 9DoF mode.
  • Experimental support!
• BMI270 (IMU_BMI270), ICM-42688 (IMU_ICM42688), LSM6DS3TR-C (IMU_LSM6DS3TRC), LSM6DSV (IMU_LSM6DSV), LSM6DSO (IMU_LSM6DSO), LSM6DSR (IMU_LSM6DSR), MPU-6050 (IMU_MPU6050_SF)
  • Using common code: SoftFusionSensor for sensor fusion of Gyroscope and Accelerometer.
  • Gyro&Accel sample rate, gyroscope offset and 6-side accelerometer calibration supported.
  • In case of BMI270, gyroscope sensitivity auto-calibration (CRT) is additionally performed.
  • Support for magnetometers is currently not implemented.
  • VERY experimental support!

Firmware can work with both ESP8266 and ESP32. Please edit defines.h and set your pinout properly according to how you connected the IMU.

Sensor calibration

It is generally recommended to turn trackers on and let them lay down on a flat surface for a few seconds.* This will calibrate them better.

Some trackers require special calibration steps on startup:

MPU-9250

• Turn them on with chip facing down. Flip up and put on a surface for a couple of seconds, the LED will light up.
• After a few blinks, the LED will light up again
• Slowly rotate the tracker in an 8-motion facing different directions for about 30 seconds, while LED is blinking
• LED will turn off when calibration is complete
• You don't have to calibrate next time you power it on, calibration values will be saved for the next use

BMI160

If you have any problems with this procedure, connect the device via USB and open the serial console to check for any warnings or errors that may indicate hardware problems.

• Step 0: Power up with the chip facing down. Or press the reset/reboot button.

  The LED will be lit continuously. If you have the tracker connected via USB and open the serial console, you will see text prompts in addition to the LEDs. You can only calibrate 1 IMU at a time.

  Flip it back up while the LED is still solid. Wait a few seconds, do not touch the device.

• Step 1: It will flash 3 times when gyroscope calibration begins.

  If done incorrectly, this step is the most likely source of constant drift.

  Make sure the tracker does not move or vibrate for 5 seconds - still do not touch it.

• Step 2: It will flash 6 times when accelerometer calibration begins.

  The accelerometer calibration process requires you to hold the device in 6 unique orientations (e.g. sides of a cube), keep it still, and not hold or touch for 3 seconds each. It uses gravity as a reference and automatically detects when it is stabilized - this process is not time-sensitive.

  If you are unable to keep it on a flat surface without touching, press the device against a wall, it does not have to be absolutely perfect.

  There will be two very short blinks when each position is recorded.

  Rotate the device 90 or 180 degrees in any direction. It should be on a different side each time. Continue to rotate until all 6 sides have been recorded.

  The last position has a long flash when recorded, indicating exit from calibration mode.

Additional info for BMI160

• For best results, calibrate when the trackers are warmed up - put them on for a few minutes, wait for the temperature to stabilize at 30-40 degrees C, then calibrate. Enable developer mode in SlimeVR settings to see tracker temperature.

• There is a legacy accelerometer calibration method that collects data during in-place rotation by holding it in hand instead. If you are absolutely unable to use the default 6-point calibration method, you can switch it in config file defines_bmi160.h.

• For faster recalibration, you disable accelerometer calibration by setting BMI160_ACCEL_CALIBRATION_METHOD option to ACCEL_CALIBRATION_METHOD_SKIP in defines_bmi160.h. Accelerometer calibration can be safely skipped if you don't have issues with pitch and roll. You can check it by enabling developer mode in SlimeVR settings (General / Interface) and going back to the "Home" tab. Press "Preview" button inside the tracker settings (of each tracker) to show the IMU visualizer. Check if pitch/roll resembles its real orientation.

• Calibration data is written to the flash of your MCU and is unique for each BMI160, keep that in mind if you have detachable aux trackers.

Uploading On Linux

Follow the instructions in this link PlatformIO, this should solve any permission denied errors

Contributions

Any contributions submitted for inclusion in this repository will be dual-licensed under either:

• MIT License (LICENSE-MIT)
• Apache License, Version 2.0 (LICENSE-APACHE)

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

You also certify that the code you have used is compatible with those licenses or is authored by you. If you're doing so on your work time, you certify that your employer is okay with this and that you are authorized to provide the above licenses.

For an explanation on how to contribute, see CONTRIBUTING.md