An ESP32 based foot pedal to communicate with the Spark Amp and Spark App via Bluetooth LE. Also works as a control device for a Looper app on the mobile.

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
• Load new presets via the Spark App
• Delete stored presets
• Control Looper apps (and other apps which support bluetooth keyboards)
• Firmware can (rudimentarily) be updated via OTA Web interface.

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

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

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
• show Bluetooth connection status to Spark Amp and Spark App and WiFi connection status

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 explain how to build and operate the pedal.

Building Ignitron

Software: click here

Hardware: click here

Operating Ignitron

Table of contents

• Operation modes
• APP 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. AMP mode can be used to manage the presets stored on Ignitron, presets can be added from the app or be deleted from Ignitron.
To enter AMP mode, hold the Preset 1 button during startup.

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 mode). 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 Bank down button. When selecting Preset mode, four buttons are used to select presets the other two buttons are used to navigate through different 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 enabled and disabled. In Manual/FX mode, the user has direct access to all effects of the selected preset. When Looper mode is activated, you can swtich between presets of the current selected preset bank and use the Bank down/Bank up buttons to control your Looper app, e.g. to record on two separate loops.

Each switch controls a different FX pedal type:

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
Bank down	Long	Switch to Looper 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
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 mode

Button	Press pattern	Function
Bank down	Short	Toggle recording on Loop 1 (can be freely configured in app)
Bank up	Short	Toggle recording on Loop 2 (can be freely configured in app)
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	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 Bank down/Bank up buttons can be freely configured to any function offered.

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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. In this mode, Ignitron's firmware can also be updated OTA via a web browser.

Connecting the Spark app with Ignitron

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 conneting 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 the 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
7. The LED of the selected preset position should start blinking
8. Hit the same Preset button a second time to confirm storage (Hitting any other Preset/Bank button will revert the state back to navigating)
9. The preset will be saved to the selected position, other presets will be pushed 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
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
Preset 2	Long	Restart Ignitron

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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 above
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 stored 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 refer to

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	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 easily 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)

OTA Updates

When in AMP mode, the firmware can be updated Over-the-air by using a web interface. In order to enable this, you need to rename the file Credentials.h.template to Credentials.h and enter your WiFi SSID and password before compiling the code. Once installed manually for the first time, subsequent firmware versions can be uploaded by opening a web browser and connecting to http://Ignitron.local and uploading the compiled Ignitron.bin file. The Ignitron should restart automatically after the upgrade finished successfully.