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. Ignitron also supports the built-in looper and additional HW presets of Spark 2.

Ignitron has been successfully tested with

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

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)
• Use the built-in Tuner
• Show Input Volume
• 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.

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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 the Tuner is switched on, the output is shown on the display and the LEDs, allowing for quick tuning while connected with the amp.
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

Button	Press pattern	Function
Bank down	Short	Navigate bank up
Bank up	Short	Navigate bank down
Preset 1	Short	Select preset 1 / Toggle Drive
Preset 2	Short	Select preset 2 / Toggle Drive
Preset 3	Short	Select preset 3 / Toggle Drive
Preset 4	Short	Select preset 4 / Toggle Drive
Preset 4	Long	Switch to Looper mode
Bank down	Long	Switch to Tuner mode. Short press while in Tuner mode to switch back to Preset mode.
Bank up	Long	Switch to FX mode
Preset 2	Long	Restart Ignitron

Manual/FX mode

Button	Press pattern	Function
Bank down	Short	Toggle Noise Gate
Bank up	Short	Toggle Compressor/Wah
Preset 1	Short	Toggle Drive
Preset 2	Short	Toggle Modulation
Preset 3	Short	Toggle Delay
Preset 4	Short	Toggle Reverb
Bank up	Long	Switch to Preset mode
Preset 2	Long	Restart Ignitron

Looper (keyboard) mode (combined with Preset functionality)

Button	Press pattern	Function
Preset 1	Short	Sends character "1" (can be freely configured in app)
Preset 2	Short	Sends character "2" (can be freely configured in app)
Preset 3	Short	Sends character "3" (can be freely configured in app)
Preset 4	Short	Sends character "4" (can be freely configured in app)
Bank down	Short	Sends character "5" (can be freely configured in app)
Bank up	Short	Sends character "6" (can be freely configured in app)
Bank down	Long	Switch to previous preset (across banks)
Bank up	Long	Switch to next preset (across banks)
Preset 4	Long	Switch to Preset mode
Preset 2	Long	Restart Ignitron

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.

Example Button setup (available commands depend on availability in the respective app):

Button	Function
Preset 1	Record/overdub current track
Preset 2	Play/pause session
Preset 3	Delete current track (press twice)
Preset 4	Mute current track
Bank down	Switch to previous track
Bank up	Switch to next track

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.

Looper control mode

Button	Press pattern	Function
Preset 1	Short	Record / Dub
Preset 2	Short	Play / Stop
Preset 3	Short	Undo / Redo
Preset 4	Short	Read current Record status from amp (only needed for analysis)
Bank down	Short	Tap tempo (repeatedly press button to adjust the tempo)
Bank up	Short	Read current looper settings from amp (only needed for analysis)
Preset 3	Long	Delete all loops (reset)
Bank up	Long	Change to Looper Config mode
Preset 4	Long	Switch to Preset mode
Preset 2	Long	Restart Ignitron

Looper config mode

Button	Press pattern	Function
Preset 1	Short	Change number of bars to be recorded
Preset 2	Short	Change feel of loop (straight / shuffle)
Preset 3	Short	Enable / Disable click
Preset 4	Short	NO FUNCTION
Bank down	Short	Tap tempo (repeatedly press button to adjust the tempo)
Bank up	Short	NO FUNCTION
Bank up	Long	Change to Looper Control mode
Preset 4	Long	Switch to Preset mode
Preset 2	Long	Restart Ignitron

---

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:

Button	Press pattern	Function
Preset 1	Short	Sends defined character (function can be freely configured in app)
Preset 2	Short	Sends defined character (function can be freely configured in app)
Preset 3	Short	Sends defined character (function can be freely configured in app)
Preset 4	Short	Sends defined character (function can be freely configured in app)
Bank down	Short	Sends defined character (function can be freely configured in app)
Bank up	Short	Sends defined character (function can be freely configured in app)
Preset 1	Long	Sends defined character (function can be freely configured in app)
Preset 2	Long	Sends defined character (function can be freely configured in app)
Preset 3	Long	Sends defined character (function can be freely configured in app)
Preset 4	Long	Sends defined character (function can be freely configured in app)
Bank down	Long	Switch to previous keyboard layout (cycling)
Bank up	Long	Switch to next keyboard layoout (cycling)

---

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)

Button	Press pattern	Function	Remark
Bank down	Short	Navigate bank up
Bank up	Short	Navigate bank down
Preset 1	Short	Select preset 1	Press twice to store received preset
Preset 2	Short	Select preset 2	Press twice to store received preset
Preset 3	Short	Select preset 3	Press twice to store received preset
Preset 4	Short	Select preset 4	Press twice to store received preset
Bank down	Long	Unload preset	Removes loaded preset if present
Bank up	Long	Toggle Bluetooth mode	Toggle between BLE and BT Serial mode
Preset 2	Long	Restart Ignitron

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)

Button	Press pattern	Function	Remark
Bank down	Short	Navigate bank up
Bank up	Short	Navigate bank down
Preset 1	Short	Select preset 1
Preset 2	Short	Select preset 2
Preset 3	Short	Select preset 3
Preset 4	Short	Select preset 4
Bank down	Long	Mark preset for deletion	Pressing any other button in that state will cancel the deletion
Bank down	Long	Delete marked preset	Only if preset was first marked for deletion
Bank up	Long	Toggle Bluetooth mode	Toggle between BLE and BT Serial mode
Preset 2	Long	Restart Ignitron

---

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

Type	App Name	Technical Name (JSON)	Parameter 0	Parameter 1	Parameter 2	Parameter 3	Parameter 4	Parameter 5	Parameter 6	Extra Info
Noise Gate	Noise Gate	bias.noisegate	Threshold	Decay
Compressor	LA Comp	LA2AComp	Limit/Compress Switch	Gain	Peak Reduction
Compressor	Sustain Comp	BlueComp	Level	Tone	Attack	Sustain
Compressor	Red Comp	Compressor	Output	Sensitivity
Compressor	Bass Comp	BassComp	Comp	Gain
Compressor	Optical Comp	BBEOpticalComp	Volume	Comp	Pad Switch
Drive	Booster	Booster	Gain
Drive	Clone Drive	KlonCentaurSilver	Output	Treble	Gain
Drive	Tube Drive	DistortionTS9	Overdrive	Tone	Level
Drive	Over Drive	Overdrive	Level	Tone	Drive
Drive	Fuzz Face	Fuzz	Volume	Fuzz
Drive	Black Op	ProCoRat	Distortion	Filter	Volume
Drive	Bass Muff	BassBigMuff	Volume	Tone	Sustain
Drive	Guitar Muff	GuitarMuff	Volume	Tone	Sustain
Drive	Bassmaster	MaestroBassmaster	Brass Volume	Sensitivity	Bass Volume
Drive	SAB Driver	SABDriver	Volume	Tone	Drive	LP/HP Switch
Amp	Silver 120	RolandJC120	Gain	Treble	Middle	Bass	Volume
Amp	Black Duo	Twin	Gain	Treble	Middle	Bass	Volume
Amp	AD Clean	ADClean	Gain	Treble	Middle	Bass	Volume
Amp	Match DC	94MatchDCV2	Gain	Treble	Middle	Bass	Volume
Amp	ODS 50	ODS50CN	Gain	Treble	Middle	Bass	Volume
Amp	Blues Boy	BluesJrTweed	Gain	Treble	Middle	Bass	Volume
Amp	Tweed Bass	Bassman	Gain	Treble	Middle	Bass	Volume
Amp	AC Boost	AC Boost	Gain	Treble	Middle	Bass	Volume
Amp	Checkmate	Checkmate	Gain	Treble	Middle	Bass	Volume
Amp	Two Stone SP50	TwoStoneSP50	Gain	Treble	Middle	Bass	Volume
Amp	American Deluxe	Deluxe65	Gain	Treble	Middle	Bass	Volume
Amp	Plexiglas	Plexi	Gain	Treble	Middle	Bass	Volume
Amp	JM45	OverDrivenJM45	Gain	Treble	Middle	Bass	Volume
Amp	Lux Verb	OverDrivenLuxVerb	Gain	Treble	Middle	Bass	Volume
Amp	RB 101	Bogner	Gain	Treble	Middle	Bass	Volume
Amp	British 30	OrangeAD30	Gain	Treble	Middle	Bass	Volume
Amp	American High Gain	AmericanHighGain	Gain	Treble	Middle	Bass	Volume
Amp	SLO 100	SLO100	Gain	Treble	Middle	Bass	Volume
Amp	YJM100	YJM100	Gain	Treble	Middle	Bass	Volume
Amp	Treadplate	Rectifier	Gain	Treble	Middle	Bass	Volume
Amp	Insane	EVH	Gain	Treble	Middle	Bass	Volume
Amp	Insane 6508	6505Plus	Gain	Treble	Middle	Bass	Volume
Amp	SwitchAxe	SwitchAxeLead	Gain	Treble	Middle	Bass	Volume
Amp	Rocker V	Invader	Gain	Treble	Middle	Bass	Volume
Amp	BE 101	BE101	Gain	Treble	Middle	Bass	Volume
Amp	Pure Acoustic	Acoustic	Gain	Treble	Middle	Bass	Volume
Amp	Fishboy	AcousticAmpV2	Gain	Treble	Middle	Bass	Volume
Amp	Jumbo	FatAcousticV2	Gain	Treble	Middle	Bass	Volume
Amp	Flat Acoustic	FlatAcoustic	Gain	Treble	Middle	Bass	Volume
Amp	RB-800	GK800	Gain	Treble	Middle	Bass	Volume
Amp	Sunny 3000	Sunny3000	Gain	Treble	Middle	Bass	Volume
Amp	W600	W600	Gain	Treble	Middle	Bass	Volume
Amp	Hammer 500	Hammer500	Gain	Treble	Middle	Bass	Volume
Modulation	Tremolo	Tremolo	Speed	Depth	Level
Modulation	Chorus	ChorusAnalog	E.Level	Rate	Depth	Tone
Modulation	Flanger	Flanger	Rate	Mix	Depth
Modulation	Phaser	Phaser	Speed	Intensity
Modulation	Vibrato	Vibrato01	Speed	Depth
Modulation	UniVibe	UniVibe	Speed	Vibrato/Chorus Switch	Intensity
Modulation	Cloner Chorus	Cloner	Rate	Depth Switch
Modulation	Classic Vibe	MiniVibe	Speed	Intensity
Modulation	Tremolator	Tremolator	Depth	Speed	BPM On/Off Switch
Modulation	Tremolo Square	TremoloSquare	Speed	Depth	Level
Modulation	Guitar EQ	GuitarEQ6	Level	100	200	400	800	1.6k	3.2k
Modulation	Bass EQ	BassEQ6	Level	50	120	400	800	4.5k	10k
Delay	Digital Delay	DelayMono	E.Level	Feedback	DelayTime	Mode	BPM Switch			Modes: 0.3 (50ms) - 0.4 (200ms) - 0.6 (500ms) - 0.72 (1s)
Delay	Echo Filt	DelayEchoFilt	Delay	Feedback	Level	Tone	BPM Switch
Delay	Vintage Delay	VintageDelay	Repeat Rate	Intensity	Echo	BPM Switch
Delay	Reverse Delay	DelayReverse	Mix	Decay	Filter	Time	BPM Switch
Delay	Multi Head	DelayMultiHead	Repeat Rate	Intensity	Echo Volume	Mode Selector	BPM Switch			Modes: 0 (Head 1) - 0.35 (Head 2) - 0.65 (Head 3) - 0.95 (Head 4)
Delay	Echo Tape	DelayRe201	Sustain	Volume	Tone	Short/Long
Reverb	Room Studio A	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.0
Reverb	Room Studio B	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.1
Reverb	Chamber	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.2
Reverb	Hall Natural	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.3
Reverb	Hall Medium	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.4
Reverb	Hall Ambient	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.5
Reverb	Plate Short	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.6
Reverb	Plate Rich	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.7
Reverb	Plate Long	bias.reverb	Level	Damping	Dwell	Time	Low Cut	High Cut	Selects Reverb Type	0.8

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.

Type	App Name	Technical Name	Parameter 0	Parameter 1	Parameter 2	Parameter 3	Parameter 4	Parameter 5	Parameter 6	Extra Info
Compressor/Wah	J.H. Legendary Wah	JH.Vox846	Auto Wah Mode	BPM Mode Switch	ms (BPM Off)	Bar (BPM On)	Sensitivity			Auto Wah Mode: 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 - Bar: 0.0 (1/8), 0.25 (1/4), 0.5 (1/2), 0.75 (1/1)
Drive	J.H. Axle Fuzz	JH.AxisFuzz	Volume	Drive
Drive	J.H. Super Fuzz	JH.SupaFuzz	Volume	Filter
Drive	J.H. Octave Fuzz	JH.Octavia	Level	Fuzz
Drive	J.H. Fuzz Zone	JH.FuzzTone	Volume	Attack
Modulation/EQ	J.H. Legendary Vibe	JH.VoodooVibeJr	Speed	Sweep	Intensity	Mix (Vibrato/Chorus)