Sparkbox, another BT pedal for the Spark

SparkBox V0.56

This is a Dev Kit 32 version of SparkBox. SparkBox is another BT pedal for the Positive Grid Spark 40. I only needed the functionality of the simpler BT pedals. However many of them use captured hex chunks to communicate with the Spark, or were Python based. Instead I wanted to use Paul Hamshere's amazing code to create and process real messages. Also I wanted to extend the functionality a bit and make a pretty UI.


  • Expression pedal input on D34 for altering the current parameter or on/off switch
  • Uses BLE so that it can be used with music function of the Spark app
  • Allows connection of the app for full simultaneous control
  • Switch presets either on footswitch, app or Spark to update display
  • Switch on and off all four major effects dynamically
  • Graphically display the effect state on the display
  • Supports 4-button pedals
  • Hold down any switch for 1s to switch between Effect mode and Preset mode
  • Battery level indicator on UI
  • BLE RSSI inidcator

Arduino libraries and board versions

Under Files->Preferences->Additional Boards Manager URLs, enter the following:

Under Tools->Board->Board manager ensure that you have the following version:

  • ESP32 by Espressif 1.0.4 (SparkBox - ESP32 Dev Module)

Under Tools->Manage Libraries nsure that you have the following libraries and versions:

  • ThingPulse SSD1306 driver 4.2.1 (SparkBox)
  • NimBLE=Arduino 1.3.1

Compile options

Uncomment ONE battery option to match your hardware.

define BATT_CHECK_0

You have no mods to monitor the battery, so it will show empty (default).

define BATT_CHECK_1

You are monitoring the battery via a 2:1 10k/10k resistive divider to GPIO23. You can see an accurate representation of the remaining battery charge and a kinda-sorta indicator of when the battery is charging. Maybe.

define BATT_CHECK_2

You have the battery monitor mod described above AND you have a connection between the CHRG pin of the charger chip and GPIO 33. Go you! Now you have a guaranteed charge indicator too.


Expression pedal define. Comment this out if you DO NOT have the expression pedal mod.

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Parts list

Item Description Link
1 Box
2 Stomp switch
3 ESP-WROOM-32U module
4 LCD screen
5 BT antenna and
6 USB extension
7 Power switch
8 DC input jack
9 Pedal jack
10 LiPo battery
11 LiPo charger
12 LiPo booster
13 9V to 5V converter
14 Glass window (opt)

More information on the Sparkbox GitHub page

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