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Help with understanting FV-1


New member
I am looking to buy pedalpcb Arachnid pcb to mess around programming my own effects and I have a few questions about programming and loading presets:

1.) I assume I can have only one program on eeprom or am I wrong?
2.) How do I connect a few eeproms to FV-1 and then choose between them?
3.) How can I load a program that is on eeprom mechanically (with switch)?
4.) How can I load a program that is on eeprom with an arduino?

Answers to questions 2, 3 and 4 will probably be fairly similar but I want to be exact.


Staff member
1) The Arachnid PCB supports up to 8 programs on an EEPROM.
2) Two different EEPROM switching mini-PCBs are in the works, in the meantime there is a thread here describing how to wire it up.
3 and 4) Changing the voltage levels of the program select pins of the FV-1 trigger a program change. The FV-1 will load the corresponding program from the active EEPROM.


New member
Can you please post a link for the EEPROM wiring thread?
How would I make an EEPROM "active"? By giving it power supply or by "turning on" a certain pin?


Staff member
To switch between more than one EEPROM you basically parallel all of the pins except for Pin 1.

Pull Pin 1 of all EEPROMs high (3.3V) through a 100K resistor. This effectively leaves them all disabled.

Now pull Pin 1 low (Ground) on whichever EEPROM you want "active". You should only have one active EEPROM at a time.

The FV-1 doesn't automatically detect that you've changed EEPROMs, so this won't force a program change. You'll need to change modes (or toggle one of the program select pins) in order to initiate a program change.


Not certain exactly what that means to "pull pin 1" - I'm a novice builder, I can wire and solder though. Can someone describe exactly how to add a toggle to switch between the internal and external programs?

On the other hand... The fv-1 datasheet mentions:

12 T1 Tie to GND for normal operation
13 T0 0: Use internal ROM programs, 1: Use programs from external EEPROM
14 SCK EEPROM clock (Internal pull up)
15 SDA EEPROM data (Internal pull up)

The arachnid schematic shows pins 14 & 15 connected to the eeprom - looks like 12 to gnd, 13 to +3.3V, which I think means pin 13 always has voltage and is therefore on (or 1) which means use the external eeprom??? Does the Arachnidc pcb, as wired, only work with the external eeprom??

So - to use the external and the internal, could one put a toggle at pin 13, ground would be 0 (zero) - use internal programs, and 3.3V would trigger use of external eeprom???

Is that right?


Well-known member
I replied to you other post, fin the leg of the resistor that conntects to pin 13 and tie a wire to that. Then you can put a switch in to connect it to ground.

edit: sorry it my response sounded curt, you’re questions are very welcome and we’re all here to learn!
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Oh NO worries dude. I did not take it as curt. I appreciate you taking the time to answer to both of my posts!