Hydra Delay Taptempo Buddy

This is adaptation of FV1Buddy tap tempo module by Electric Canary for use with Hydra multi-head Delay by PedalPCB (also available as a kit at musikding.de).

NOTE: this project is not fully finished yet. Firmware generally works, but is under testing still. One additional feature is in my head also. HW part is also under testing, schematic will be updated once HW is finished and PCB designed.

Tip: You can use my Simple Serial UPDI programmer for tis project.

Features

• Delay time/tempo can be controlled by Time Pot or tapped by Tap Button.
• Tap Tap Button at least two times to switch from Time Pot controll to Tap Button conntroll.
  • Second tap must follow under 1,7s after first one.
  • Subsequent tap times are averaged until tapping finishes.
  • Tapping finishes if next tap is not performed for at least 3 times of the currently tapped tempo - LED blinks in the tapped tempo then
• Move Time Pot at least 5% to switch controll back to it - LED is on without blinking then
• Tap to Head switch (optional)
  • selects if tapped tempo targets Head 2 or Head 4. Tapping to Head 2 allows you easily set tempo in "eights" for "dotted eigts" played by Head 3.
  • switch change is not used immediatelly, but for the next tapping. Also used after next pedal power-on.
• current Time Pot or Tap Button controll mode, together with the tapped tempo, is preserved over the pedal power-off.

Applying module into Hydra effect

It is really easy:

• Plan tap tempo module and all new controls placement in the pedal enclosure. Use long enough wires for the placeent.
• Do not solder Speed pot to the Hydra PCB, but connect its pads to the module instead:
  • right most square one to GND - ground for the module.
  • center one to O - tempo voltage from the module back to the Hydra.
  • left one to 3V3 - 3,3V power for the module.
• Time Pot - connect Speed pot 1, 2 and 3 lugs to the module's P1, P2 and P3. Use B type pot, from B10k up to Hydra's original B100k. Use Time or Speed or Delay label for the pot as you prefer ;-)
• Tap Button - connect momentary button to the module's TAP pads.
• LED - connect LED to the module's L+ and L-. Use TL trimmer to set LED's brightness. Used 2k value should be OK for the most LED types, if too small for your LED, use higher trimmer value, or connect additional resistor. in series. Alternatively use fixed value resistor RL.
• Tap to Head switch - optional, single on/off switch, connect it to the module's DIV pads. Pads connected together is tapping to Head 4, disconnected is Head 2.

ToDo Image How to connect taptempo module to Hydra PCB

Building module

Module schematics:

PCB BOM:

Markings	Value	PCB packaging type
R1, R2	1k	1206
R4	10k	1206
C1, C3, C4	100n	1206
C2	10u	5,3mm
TL	2k	sorry, from my stash, no idea about the type
RL (instead of TL)	matching LED	1206
U1	ATtiny 402 or 412	SOIC-8
UPDI		3 pins header connector (male or female, it's on you)

External components:

Markings	Value
Time Pot	B10k - B100k
LED	any color and size LED
Tap Button	any momentary switch
Tap to Head	any on/off switch

PCB:

Project Content

• ToDo .hex - firmware binary
• firmware/ - VSCode/PlatformIO project with firmware
• FV1BuddyForHydra.dch - schematics
• FV1BuddyForHydra-rev1_gerber.zip - Gerber file for PCB fabrication
• FV1BuddyForHydra.dip - PCB design file

Schematics and PCB design file can be opened/edited by DipTrace.

Changes from FV1Buddy

FV1Buddy was forked in June 2025. It was not finished and some code parts didn't work correctly at the fork time.

Functional changes:

• Hydra maximum delay time is used by default (no callibration necessary)
• "Tempo Division Switch" allows to select taping for "Head 2" or "Head 4" of the pedal. It is read as a binary input and is fully optional - defaults to "Head 2" if omitted.
• "48kHz Clock Output" and related functionality is removed
• long Tap initiated 'RAMP' feature removed

Non-functional changes:

• "Momentary Tap Tempo Button Input" moved to microcontroller's pin freed by remove of "48kHz Clock Output". So UPDI pin is not used and "UPDI High-Voltage Activation" capable programmer is not necessary. You can use my Simple Serial UPDI programmer and program u-controller on the board using UPDI header pins.
• Added hardware debounce circuit for the Tap Tempo button.
• Corrected computiong of the pwm value when Tab button is used.
• EEPROM storing code chaged, avr/eeprom'h haven't work for me (but it might be due to next problem found later ;-).
• Implemented delayed tap=0 storing into EEPROM to keep tap=1 during power-off, as Time Pot value change may be detected by u-controller as power voltage drops.
• Distinct code optimizatios.
• Lots of comments added as I learnt the code.

All changes are marker by MOD: comment in the source code as accurate as possible.

License

© 2025 - 2026 ElvisAlive Tone. This work is openly licensed via CC BY-SA 4.0