A self contained, Arduino compatible board for applying audio DSP. The intended purpose is to equalize and apply bass boost to BMR VR off ear headphones, but can be adapted for any other light DSP tasks by SGTL5000 codec.
Supports:
- 7 band prarametric or 5 band graphic EQ.
- AutoEQ profiles for 1000+ headphones and earbuds.
- Psycho-acoustic bass boost to over come limited bass response of small headphone drivers.
- Stereo surround expansion.
- Automatic volume control.
Please see the SGTL5000 documentation for all DSP features. Credit to Paul Stoffregen of PJRC.com for creating the Teensy Audio library (we're reusing a SGTL5000 component in the code).
TODO:
- Make use of the USER button for switching between presets.
- Plug in a USB power source. Anything from computer, phone, Quest/Quest 2 or some USB power bank (see below) should work.
- Plug in 3.5mm stereo jack from audio out to LINEIN.
- Plug your headphones into OUT.
NOTE: the OUT port is designed to drive headphones. It may not work as intended as an input into another audio device.
The latest version of the firmware allows you to config the DSP settings with Chrome browser through WebUSB.
To enter and use the WebUSB mode:
- Connect the board to your computer with a USB cable.
- Open a recent version of Chrome.
- Press and hold the USER button while pressing the RESET button.
- Release the USER button when the LED light turns off.
- Chrome should recorgnize the device as 'QT Py M0'.
- Click on the notification to go to the configuration page (https://tanvach.github.io/prettygood_dsp/).
- Click 'Connect' to pair and connect to the board (only needs to be done once).
- The LED light will turn on when WebUSB connection is established.
Most USB power banks will turn off when powering the board, since the current draw is too low.
- Some brands will allow 'low power draw' mode by holding the on button for few seconds (i.e. Xiaomi).
- A list of tested power banks that support low power draw https://www.candlepowerforums.com/vb/showthread.php?440476-USB-powerbank-WITHOUT-auto-off
- Use a USB splitter cable to power both the headset and DSP board (see below).
- Try using the 'Pulse USB Power' to periodically consume more power.
This feature will turn on the MCU DAC and periodically output max voltage to the A0 pin. This by itself consumes ~35mA of power. This is enough for some USB batteries to keep them awake. If not, you can conenct a short wire between A0 to GND to comsume even more power (~50mA). Adding this wire should be enough (tested with Anker branded batteries).
This splitter cable is confirmed to work with Oculus Link and from power bank. It takes a Micro USB connection and split into USB-C (provides power and USB 2.0 data) and Micro USB (provides power only).
Alternatively, you can also use this USB-C PD charging + USB-C headphone splitter. The headphone port provides enough power to power the DSP.
The board firmare is updatable via USB.
- Connect the DSP board via USB and double clicking the RESET button. This triggers the boot loader mode.
- Check that the blue LED stays on and QTPY_BOOT drive is mounted on your desktop.
- Download 'firmware.uf2' file and copy it to the QTPY_BOOT drive. It should unmount automatically.
- The firmware update is complete. You can now disconnect the USB cable.
If you want to make changes to the firmware, you'd need to follow these steps.
This board comes with a fail-safe bootloader mode, making it almost impossible to brick by updating the firmware through USB.
You need to first install VSCode, then Platform IO by following these instructions.
Download this repository using git clone command, or download and extract the zip file on your computer.
In VSCode (with Platform IO installed), choose 'Open...' or 'Open Folder...' and select this repo's 'prettygood_dsp' folder.
Once you're happy making changes, select 'main.cpp' file and click the checkmark button at the bottom of VSCode to build the new firmware.
Platform IO will fetch all the dependencies automatically for you and compile the code. The file 'firmware.uf2' will be overwritten with the new version.
To upload the firmware, follow the 'Update firmware' section above.
- Adafruit Zero I2S
- RTCZero
- Adafruit TinyUSB Library
- ArduinoJson
- FlashStorage
The board is designed based on Adafruit SAMD21 QtPy. The default bootloader is vanilla SAMD21 QtPy and can be download from Adafruit SAMD UF2 repo. The only difference is that we've replaced the NeoPixel with a blue LED.
The schematic can be found here.
The advantage of using this bootloader is that any projects that can run on SAMD21 boards (Aduino Zero, QtPy, Trinket M0, Feather M0) can theoretically run on Prettygood DSP.
One limitation - the I2S peripheral needs to be on to provide clock signals to the SGTL5000 codec. So the I2S/SPI pins are not available as GPIO. Otherwise the TX and A0-A3 pins are free and available.
Contributions are welcome!