An ESP32 based foot pedal to communicate with the Spark Amp and Spark App via Bluetooth LE (iOS) and Bluetooth Serial (Android). Also works as a control device for a Looper app on the mobile. NEW: Ignitron also supports the built-in looper of Spark 2! Ignitron has been successfully tested with

• Spark 2
• Spark 40
• Spark Mini
• Spark GO

(Note: On Spark 2, Ignitron supports only the first bank of HW presets so far. The rest is fully functional.)

Ignitron gives you full control over your Spark Amp:

• Switch between the four hardware presets
• Switch between custom saved presets organized in banks
• Toggle effects for the selected preset
• Save new presets to Ignitron via the Spark App
• Delete stored presets
• Control the Spark 2 internal looper.
• Control Looper apps on a mobile (actually all apps which support bluetooth keyboard controls)
• Multiple BT keyboard layouts configurable

Adding new presets to Ignitron can easily be done as it can also act like a Spark Amp. Simply connect to Ignitron with the Spark App and save new presets directly from ToneCloud (or your downloaded presets) to Ignitron.

One big advantage of Ignitron is that it communicates with the Spark Amp using the Bluetooth LE protocol. This means it is possible to connect your mobile to your Spark Amp as an audio speaker and play along your favorite songs while you control your effects with Ignitron.

The current active preset and effects are indicated via LEDs.\ In addition, the built-in display provides information on

• selected bank and preset number
• selected preset name
• operation mode (Preset, Manual/FX, Looper)
• activated pedal types in the FX chain
• Bluetooth connection status to Spark Amp and Spark App

This work was inspired by the Sparkpal project, and the Python Spark Parser project helped me to understand the messages being sent to and from the Spark Amp.

The following sections show how to build and operate Ignitron.

Building Ignitron

Software: click here

Hardware: click here

Operating Ignitron

Table of contents

• Operation modes
• APP mode
• Keyboard mode
• AMP mode
  • Storing a new preset
  • Deleting an existing preset
  • Manually creating presets
  • Preset format
  • FX parameter reference
• OTA Update

Operation modes

Ignitron has two operation modes, APP mode and AMP mode.\ In APP mode (default mode on startup), Ignitron connects to a Spark Amp and behaves like the Spark App towards the Spark Amp. It can then be used to switch between saved presets, toggle FX pedals, and even connect it to a Looper app on a mobile (providing 6 buttons to control a (looper or tabs) app).

AMP mode can be used to manage the presets stored on Ignitron, presets can be saved via the app or be deleted from Ignitron. For Android, the Bluetooth mode has to be set to Serial (SRL), for iOS it has to be set to BLE.\

Keyboard mode is useful when Ignitron should act as a bluetooth keyboard control without controlling a Spark Amp. This provides 2x6=12 buttons to control any supporting app (e.g., a looper or a tabs app).

To enter AMP mode, hold the Preset 1 button during startup. To enter Keyboard mode, hold the Preset 3 button during startup.

Amp mode and Keyboard mode can best be started by holding the respective button pressed while pressing and holding Preset 2 button to reset.

A graphical overview of all modes with button mapping can be found here. (Thanks to @itarozzi for creating this.)

APP mode

In APP mode, the foot switches can be used to either switch between pre-saved presets (Preset mode), control all single effects in the selected preset (Manual/FX mode), or switch between presets while controlling an app on your mobile, e.g. a Looper app (Looper (keyboard) mode). If connected to a Spark 2 amp, the Looper (amp) mode will control the internal looper of the amp. You can easily toggle between Preset mode and Manual/FX mode by long pressing the Bank-Up button. To toggle between Preset mode and Looper mode, simply long-press the Preset 4 button.

When selecting Preset mode, four buttons are used to select presets, the other two buttons are used to navigate through the preset banks. This way the user has access to a huge number of saved presets. When pressing the foot switch of the current active preset, the effect configured in the DRIVE section can be toggled.\ In Manual/FX mode, the user has direct access to all effects of the selected preset. Pressing a switch will toggle the respective FX type.\ When Looper (keyboard) mode is activated, Ignitron acts partially like a bluetooth keyboard. You can use the buttons to control a looper app, e.g. Loopy HD, and also switch between stored presets by long pressing the Bank down/Bank up buttons. Note: When switching presets in Looper mode, it will do this across banks.
When Looper (amp) mode is activated, Ignitron will control the internal looper of the Spark 2 amp. The display will also show information on the looper settings and click. The amp looper settings can easily be changed using Ignitron.

Button commands in APP mode:

Preset mode

Manual/FX mode

Looper (keyboard) mode (combined with Preset functionality)

Note: In Looper mode, Ignitron is connected to your mobile as a bluetooth keyboard. If supported by the respective app on the mobile, the buttons can be freely configured to any function offered by the respective App. You may need to manually connect to the Ignitron BLE keyboard in your Bluetooth settings after switching to Looper mode.

Looper (amp) mode (to control the Spark 2 looper)

The preset buttons 1-3 mimick the three looper buttons on the amp, the LED status should match the LEDs on the amp. With long pressing the Bank up button, Ignitron will toggle between Looper control mode and Looper config mode. The current mode will be shown by a 'L' or 'C' in the display respectively.

Keyboard mode

This mode will turn the Ignitron into a Bluetooth LE keyboard. All buttons will act like keyboard presses, there is no functionality regarding Preset change or other Spark Amp related functions. Use this mode if you want to only use Ignitron as a looper control device (or any other supporting app like a tabs app) . If you want to use looper control in combination with Spark Amp control, use the Looper mode as part of the APP mode (see above). In the code, multiple different keyboard layouts can be defined to support various apps. In operations, Ignitron can switch between these keyboard with the press of a button.

Every key needs be configured with the following parameters:

• Key ID (1-6 for short presses, 11-14 for long presses)
• Key code
• Modifier key (Shift, CTRL, etc.)
• Key press repetitions (0 for single press)
• String representation of key in display (should only be 1 character)

In operations, when a button is pressed, the corresponding key including modifiers will be sent to the connected device. The display will show the key representations of the currently active keyboard. The standard defined keyboard layout will send characters 1 to 6 for short presses and characters A to Dfor long presses.

Example:

{
  1,
  0xD8, // KEY_LEFT_ARROW
  0x81, // KEY_LEFT_SHIFT
  2,
  "<"
}

If a key is configured like the above, a button press will send the combination of the LEFT SHIFT and LEFT ARROW keys with 2 repetitions. In the display the key will be shown as <. Long pressing Bank down and Bank up are reserved for keyboard layout switching.

Key codes for special keys can be found here: BLE Keyboard Library

In keyboard mode, the following keys will be sent to the connected device:

AMP mode

In AMP mode, Ignitron acts like a Spark AMP and can communicate with the Spark app running on a mobile. New presets can be stored on Ignitron and existing presets can be deleted.

Connecting the Spark app with Ignitron

Note: By default, Ignitron is configured to use BLE which only works with iOS. In order to connect an Android device, you need to switch to Serial Bluetooth. To do so, press and hold the Bank Up button when in AMP mode (after step 1. below). This will toggle the Bluetooth mode and restart Ignitron. After toggling the Bluetooth mode, start with step 1. below again. Ignitron persists the Bluetooth mode over restarts.

1. Start Ignitron in AMP mode (hold Preset 1 button during startup).
2. Open the Spark App on the mobile
3. For the first connection, make sure to have your real Spark Amp powered off to avoid the app connecting to it.
4. Hit the connect button in the app (or the + button in the connection overview)
5. Once the connection is established, you can give the connection a name in the app so you can distinguish from your regular Spark Amp connection.

Storing a new preset (a preset from the app needs to be loaded)

1. Start Ignitron in AMP mode (hold Preset 1 button during startup).
2. Connect the Spark App with Ignitron (see above)
3. Select a preset in the app (either saved in the app or from ToneCloud).
4. The preset name should appear in the bottom line of the display
5. The Preset/Bank buttons on Ignitron can be used to navigate to the desired preset position.
6. Press the Preset button to mark the position for storing (the LED of the selected preset position should start blinking)
7. Hit the same Preset button a second time to confirm storage (Hitting any other Preset/Bank button will revert the state back to navigating)
8. The preset will be saved to the selected position, other presets will be pushed one position back

Button commands (case: preset has been received from Spark app)

Deleting a preset (only possible when no preset from the app is loaded)

1. Start Ignitron in AMP mode (hold Preset 1 button during startup).
2. Use the Preset/Bank buttons on Ignitron to navigate to the desired preset position
3. Long press the Bank Down button to mark the selected preset for deletion
4. The LED of the selected preset should start blinking
5. In the display you should see a prompt if deletion should be executed
6. If you want to cancel the deletion, simply short press any other button
7. Otherwise, long press the Bank Down button again to confirm deletion. (Hitting any other button will cancel the deletion and return back to navigation)

Button commands (case: no preset has been received, slot is empty)

Manually creating presets

This method is only recommended if a preset cannot be transferred via the Spark app or if the preset files have been received/generated in a different way.

1. Create a preset file in JSON format as shown below
2. Make sure the file name does not exceed 31 characters (including the .json suffix)
3. Put the file name into the data folder
4. Insert the file name (including the .json suffix) to the desired prefix location in the PresetList.txt file
5. Place the PresetList.txt file into the data folder (if not already there)
6. Upload the data folder to Ignitron via the Arduino IDE (or other tools)

Preset format

Ignitron stores presets in a JSON format using the SPIFFS file system. Each preset is stored in a separate file and presets are organized in a separate text file called 'PresetList.txt'. This list simply stores the file names of the presets, the order defines the way the banks are filled. An example preset file would look like this:

{"PresetNumber": 127, "UUID":"DEFBB271-B3EE-4C7E-A623-2E5CA53B6DDA",
"Name":"Studio Session" , "Version":"0.7", "Description":"Description for Acoustic Preset 1", "Icon":"icon.png", "BPM": 120.0000,
"Pedals": [
  { "Name":"bias.noisegate",  "IsOn": false,  "Parameters":[0.5000,0.3467] },
  { "Name":"BBEOpticalComp",  "IsOn": true,   "Parameters":[0.7583,0.2585,0.0000] },
  { "Name":"DistortionTS9",   "IsOn": false,  "Parameters":[0.1396,0.4073,0.6898] },
  { "Name":"Acoustic",  "IsOn": true,   "Parameters":[0.6398,0.3851,0.3834,0.5994,0.5195] },
  { "Name":"ChorusAnalog",  "IsOn": true,   "Parameters":[0.8417,0.2275,0.9359,0.3513] },
  { "Name":"DelayMono",   "IsOn": false,  "Parameters":[0.2240,0.2112,0.4909,0.6000,1.0000] },
  { "Name":"bias.reverb",   "IsOn": true,   "Parameters":[0.7228,0.3262,0.2758,0.3607,0.3439,0.4860,0.4000] } ],
"Filler":"23"
}

As a guidance which effect and amp names can be used and in which order the parameters of each effect have to be given, please see below.

FX parameter reference

In order to know which effects are available with paramters, see below table. This data can be used to build own presets in JSON format (see above). Use the Technical Name information in the JSON files. Parameters marked with Switch can only have values of 0 or 1, others can have any value between 0 and 1.

Standard Tones

Hendrix Tones

Note: You can simply store tones using Hendrix gear on Ignitron. As the effects are licensed and purchased In-App, you need to connect your mobile Spark App to the Spark Amp after switching on the Spark Amp. When you then disconnect the Spark App and connect Ignitron afterwards you should be able to use presets using below gear.