EEPROM selection PCB

Which method would you prefer for mounting the EEPROM selector board?

  • Method 1: PCB mounts to toggle switch

    Votes: 10 52.6%
  • Method 2: PCB mounts to EEPROM socket, toggle switch is wired offboard

    Votes: 9 47.4%

  • Total voters
    19

PedalPCB

Administrator
Staff member
I'm working on a small adapter PCB for the FV-1 to allow toggling between two EEPROMs on a toggle switch.

Right now I'm torn between two different methods...

  1. PCB mounts to toggle switch, 4 wires connect to main PCB (VCC, GND, SCL, SDA)
  2. PCB plugs into EEPROM socket with pin headers, 3 wires connect to enclosure-mounted toggle switch.

Whats your preference?
 

zgrav

Active member
both approaches seem reasonable. option 2 probably lets the toggle switch fit in some tighter spots on a pedal.
 

I Love Music

New member
Whichever choice, make sure to leave enough vertical space for an 8pin dip socket on one side (or both), so we can swap eeprom chips as you make new sounds available.

I'm certain I'm not the only person who sockets their eeprom chips here ?
 

I Love Music

New member
I'd say option two, because when you use I2C (SDA, SCL) between two chips, it's best practice to keep all connections as short as possible, and not to run the 2-wire signal through physical disconnects; sockets introduce problems, as do separate ground planes.

Even at the protocol's lowest speeds, keep conductive interconnects short to avoid reflection errors in the data stream (which I'm not sure the FV-1 can recover from gracefully as it loads programs) and to avoid putting high frequency noise near the op amps, which may cause gain overload (oscillation) at inaudible frequencies, and mess with the sound of the guitar.

I'd suggest trying it both ways but with an oscilloscope set to about 200uS on your audio signal to check for stray RF from the scl/sda pair, which you might twist several times to cancel reflections, unless you go with shielded cable.

I'm not being a know-it-all ... I'm humbly sharing what I've learned about mixing I2C and audio within a music project. I use arduino chips to control FV-1s in my personal projects, which use an sda/scl pair from a rotary encoder to choose which effect on my Arachnid board to engage, and another sda/scl pair to send that effect name to a display. I have a box of "mistakes" PCBs to back up the above suggestions about signal quality, data paths, and shielding with this signal combination.
 

Cybercow

Member
If both are possible with the option to do either, that would be my choice. If it comes down to only one of the two, then I would opt for #1. It seems sturdier than a PCB daughterboard plugged into an 8-pin DIP socket.

But then option #2 offers the potential for a slightly larger PCB daughterboard with 4 EEPROMs on it in the near(er) future. Still, I'm good with #1 if it's one or the other.
 

I Love Music

New member
Should I save some space in my current FV-1 build for a EEPROM switcher?
THAT is a VERY important question !

What are the dimensions of the switch-mounted eeprom board ? Must it occupy space near the stomp switch where there is no PCB above it ?

What is the height of the socket-mounted onboard assembly ? What keeps it firmly mounted to the DIP-8 socket ?

PPCB Administrator, can you share the (projected) sizes of these items so we can consider drilling and layout for the extra switch ?

(with many thanks to PPCB for making this item)
 
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