# Arachnid - Dual Eeprom



## phi1

This is my 2nd Arachnid build, my first was the old version with the potentiometer to select patches.  This new version with the 8-way switch is much nicer.

Since PedalPCB hasn't released a dual eeprom board yet, I had to cobble together my own on perfboard.  If @PedalPCB does release a dual eeprom board, this would be the configuration I'd vote for, since the most obvious application is to use it on an Arachnid board, and I was able to keep it in a 125B.  It was a little tight having the switch at the top under the power jack, but doable.

I included shots of the dual Eeprom daughterboard, and a drawing of the layout.  Following info previously provided from PedalPCB, you can select Eeproms by manipulating Pin1.  Pin1 low (0v) is activated, Pin1 high (3.3v) is deactivated.  As he also noted, fliping the toggle switch doesn't automatically change programs, you have to move the 8-way selector switch before the fv-1 will recognize a program change.

It was tricky soldering the pin headers onto the bottom side of the perfboard, since I had to leave a space between the plastic and the perfobard to get the iron in there.  I just noticed that in the pictures that you can see I didn't get solder to fill all the way around on some of them (oops), but the connections all still registered with the multimeter.  I used a piece of white foam from Tayda's dip socket packaging to support the cantilevered part of the daughterboard.  I had to be careful about the order of soldering (8 way switch, then daughterboard, then mix pot).

For Bank A I used mostly spacialist reverb patches, with a code tweak on the shimmer so that it's only octave up. For the B side, it's a mix of PedalPCB patches (kaleidescope and sample hold), patches I found online, and some I wrote myself.  I used my dev board build with exterior eeprom socket to test all the patches and flash the A and B chips.

**EDIT** - the pdf on my original post had an error on the perfboard layout (see p_wats comment on 8/10/2020).  I marked up and reattached the pdf.


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## zgrav

is that one of the Lego lenses for the LED?  nice job with the layout.


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## phi1

zgrav said:


> is that one of the Lego lenses for the LED?  nice job with the layout.


Haha I did see someone do that on here.  No, mines just the 5mm type 1 bezel from here.  

I forgot to mention I used an RGB LED from tayda, with the blue and green diodes activate (one resistor for each).  That's what's on the little vero board under the LED.  It turned out cool because it's kind of a sea blue / sea green look, and depending on the angle you look at it it's more blue or green.  I sanded the outside of the clear bulb of the LED to make it more diffuse too to help it all blend better.


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## p_wats

Cool! I've been tempted to do this same thing, but haven't found the time. Glad I can copy your example now if need be! Thanks.


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## Many__Of__Horror

Thank you for the detailed write up on this.


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## Sasan

WOW, this is fantastic!


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## Chuck D. Bones

Most impressive, inside & out!


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## Barry

Very nice, love the art!


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## phi1

Thanks guys. Credit for the art goes to my buddy who is a graphic designer. We have a good thing going where I’m teaching him to build pedals and he occasionally does some design work for me. Even though I’ve done a bunch with water slide now, I still don’t have it down perfect, but fortunately the imperfections on this one were minor.


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## Funnel

Looks awesome! love the addition of the selectable EEPROM


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## Mourguitars

Looks awesome phil1 !


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## p_wats

@phi1 I hope you don't mind the thread revival, but I'm fascinated by this and want to adapt the layout to fit an older Arachnid board (EEPROM on the other side, so it all has to be swapped to fit). 

I understand the schematic (thanks for that!) but it looks like the perf drawing always has pin 1 of the first socket grounded (as it's connected to the pin header that would be grounded by the PCB connections). 

I just mocked up a version and the only way it worked was to remove that connection to the first pin header and let the switch takeover deciding which pin 1 was actually grounded. 

Does that make sense?


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## phi1

oh man you're right!  So sorry!  I don't have that unit anymore, but looking at the pics I posted (particularly that angled view of the solder side), I don't think I made that connection.  I'm guessing what happened is when I initially wired the board up, I probably made a really crude diagram that was correct, then copied it wrong for the presentable version (although I thought I checked over it so many times haha!)

I'll add an edit to my original post.  Good luck with your journey on the mega fv-1 pedal (I hope my bad diagram wasn't the cause of all your woes...)


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## p_wats

phi1 said:


> oh man you're right!  So sorry!  I don't have that unit anymore, but looking at the pics I posted (particularly that angled view of the solder side), I don't think I made that connection.  I'm guessing what happened is when I initially wired the board up, I probably made a really crude diagram that was correct, then copied it wrong for the presentable version (although I thought I checked over it so many times haha!)
> 
> I'll add an edit to my original post.  Good luck with your journey on the mega fv-1 pedal (I hope my bad diagram wasn't the cause of all your woes...)



No problem at all. I'm just happy I can apparently still read a schematic after somehow screwing up that last build so badly. Ha.

Those issues definitely weren't the fault of anything here, as I tried the same daughter board in another working build (brave/stupid, I know) and it didn't do any damage, just no sound.

I'm going to build up a few of these for my remaining Arachnids, so thanks for posting this!


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## phi1

Here’s a version I drew up for a strip board layout in case you prefer that. I made it for someone who said they weren’t familiar with building on strip board, hence the over the top detail.

I haven’t tested it, but I checked over it and I think it’s good, let me know if you notice any errors.


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## p_wats

phi1 said:


> Here’s a version I drew up for a strip board layout in case you prefer that. I made it for someone who said they weren’t familiar with building on strip board, hence the over the top detail.
> 
> I haven’t tested it, but I checked over it and I think it’s good, let me know if you notice any errors.



That's great. Thanks for sharing. Very thorough! 

I do build more often in vero, so I coincidentally drew up my own layout last night as well for the two newer Arachnids I have.


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## p_wats

For what it's worth, I wanted to learn DIY Layout Creator anyway, so this is the layout I used for_ my double Arachnid pedal_. My board sockets weren't the type that would accept pin headers, so this layout has been adapted for wired connections (one row wider). It works great!


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## phi1

Sweet!


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## adolfo

phi1 said:


> This is my 2nd Arachnid build, my first was the old version with the potentiometer to select patches.  This new version with the 8-way switch is much nicer.
> 
> Since PedalPCB hasn't released a dual eeprom board yet, I had to cobble together my own on perfboard.  If @PedalPCB does release a dual eeprom board, this would be the configuration I'd vote for, since the most obvious application is to use it on an Arachnid board, and I was able to keep it in a 125B.  It was a little tight having the switch at the top under the power jack, but doable.
> 
> I included shots of the dual Eeprom daughterboard, and a drawing of the layout.  Following info previously provided from PedalPCB, you can select Eeproms by manipulating Pin1.  Pin1 low (0v) is activated, Pin1 high (3.3v) is deactivated.  As he also noted, fliping the toggle switch doesn't automatically change programs, you have to move the 8-way selector switch before the fv-1 will recognize a program change.
> 
> It was tricky soldering the pin headers onto the bottom side of the perfboard, since I had to leave a space between the plastic and the perfobard to get the iron in there.  I just noticed that in the pictures that you can see I didn't get solder to fill all the way around on some of them (oops), but the connections all still registered with the multimeter.  I used a piece of white foam from Tayda's dip socket packaging to support the cantilevered part of the daughterboard.  I had to be careful about the order of soldering (8 way switch, then daughterboard, then mix pot).
> 
> For Bank A I used mostly spacialist reverb patches, with a code tweak on the shimmer so that it's only octave up. For the B side, it's a mix of PedalPCB patches (kaleidescope and sample hold), patches I found online, and some I wrote myself.  I used my dev board build with exterior eeprom socket to test all the patches and flash the A and B chips.
> 
> **EDIT** - the pdf on my original post had an error on the perfboard layout (see p_wats comment on 8/10/2020).  I marked up and reattached the pdf.


hi phi.. great job!! did you solve the issue that make you use the rotary to recognize the changes?

TIA


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## phi1

Thanks!

No, that’s a limitation of the fv-1 chip. The fv-1 only fetched the data from the eeprom when it detects a change on pins 16-18. Flipping the A/B toggle doesn’t affect pins 16-18, it just affects which eeprom chip will be active when the fv-1 fetches the data. So, when the toggle is flipped, the fv-1 doesn’t know to fetch new eeprom data until you move the rotary.

Hope this helps


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## adolfo

phi1 said:


> Thanks!
> 
> No, that’s a limitation of the fv-1 chip. The fv-1 only fetched the data from the eeprom when it detects a change on pins 16-18. Flipping the A/B toggle doesn’t affect pins 16-18, it just affects which eeprom chip will be active when the fv-1 fetches the data. So, when the toggle is flipped, the fv-1 doesn’t know to fetch new eeprom data until you move the rotary.
> 
> Hope this helps


Thanks !!!


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## Moltenmetalburn

So I’ve been looking at this and it seems based on the schematic drawn that the pins I marked in green should be connected together/toground as well but are not in the layout drawing?

Is this actually verified at this point?

I want to give it a shot.


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## phi1

Thanks for the comment, yes those pins should also connect to ground. I didn’t link them in my layout, because my layout assumes you’re using pin headers (or resistor legs) to connect it to the pcb (squares on my layout). So pins 3&4 will connect to ground because the pin headers go to the pcb, and those pcb pads are grounded.

I did build it using that layout and it worked, I don’t think anyone else has.  Careful the order you solder on the pots / this board. 

Admittedly, it’s a little tricky connecting all those links on perf board like this. If I were to build it again I’d use vero (stripboard) using the layout from my pdf (aug 11 post, haven’t verified) or the one p_wats made (he built so it’s verified).


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## Moltenmetalburn

Thanks to all who worked this out together here and shared enough info for me to put this together. It actually sat here unverified for a long while, I needed a second eeprom lol.

Finally got around to verifying it and all is perfect. The internal switch was simply to verify before drilling a hole and running wires to the pads.

If anyone wants one PM me to discuss, I guess I can’t keep them all to myself haha.


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## phi1

Awesome! That is EXACTLY how I envisioned it working with a pcb.  Would be much easier to solder the headers with pcb compared to vero or perf.


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## Sasan

Moltenmetalburn said:


> View attachment 11122
> Thanks to all who worked this out together here and shared enough info for me to put this together. It actually sat here unverified for a long while, I needed a second eeprom lol.
> 
> Finally got around to verifying it and all is perfect. The internal switch was simply to verify before drilling a hole and running wires to the pads.
> 
> If anyone wants one PM me to discuss, I guess I can’t keep them all to myself haha.


WOW, this is aweome! I'd love to get one (if you ship internationally....I think I'd replace the internal switch with an on/on-toggle and put it on the outside of the enclosure...)


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## JamieJ

This is amazing. I would happily buy one too.


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## Moltenmetalburn

Sasan said:


> WOW, this is aweome! I'd love to get one (if you ship internationally....I think I'd replace the internal switch with an on/on-toggle and put it on the outside of the enclosure...)


The pads are meant specifically for that, as I mentioned I placed the switch to verify the pcb was working correctly before drilling hole into enclosure, just in case.

  👌🏼PM me for contact info, I will sell you one.


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## Moltenmetalburn

JamieJ said:


> This is amazing. I would happily buy one too.


PM me for contact info.


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## Bricksnbeatles

heretop said:


> I am going to try this but with three eeprom, with this switch to switch between three eeprom. Will it work or any suggestion?
> View attachment 11542


That should work. In the thread I made a while ago about this idea, @PedalPCB mentioned that he might make daughterboards for both that configuration and for a 1p8t rotary switch.


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## phi1

Yeah I’m kinda with you there, a toggle switch can be snuck into the 125B build with the current layout. 2 or 3 banks is probably as high as I’d want to go personally. Though a 64 patch diy project is an epic concept.


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## phi1

Hmm to be honest I’m not sure. I don’t have the unit pictured any more to look at for reference. If I recall right it was a tight squeeze just for the single row toggle. You could consider mounting the switch on the side, or below the rotary. In this case it’s be above the pcb, which toggle switches don’t quite fit in the same height of normally mounted pots. There’s some extra length on pot and rotary switch pins so you could make the pcb a bit higher, not sure if that would give you enough to fit the toggle. Or put a short shaft sw right next to the stomp. Seems dangerous, but I’ve done it and thought there wasn’t really any chance of stomping the switch.  Though that might not be ideal for you aesthetically.


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## JamieJ

Hi @phi1 - Can I ask why you chose 51k for the resistors? I notice that @Moltenmetalburn  has used 10k for his PCB. What is their purpose with this mod?


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## phi1

Any value will work fine, from 10k to 100k (and beyond to some extent).

Basically, if pin1 is connected to ground, then pin1 is at 0v. Current flows from 3.3v to ground through the resistor. (If 10k, I=0.33mA of wasted current, not significant in my opinion, higher resistor is less current through this path). 

if pin 1 is not grounded, then pin1 will sit at about 3.3v, pulled high through the resistor (called pull-up resistor). Technically, it’s a voltage divider formed by the resistor and the input impedance of the chip pin1. I don’t know what this impedance is actually, but I assume it’s high enough that 100k resistor keeps it plenty close to 3.3v.

the same idea (pull-up or pull-down resistor) is used on the arachnid for pins 16-18 (program selection), and pin13 if you choose to add a switch to ground pin13 for fv-1’s stock internal patches.


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## JamieJ

phi1 said:


> Any value will work fine, from 10k to 100k (and beyond to some extent).
> 
> Basically, if pin1 is connected to ground, then pin1 is at 0v. Current flows from 3.3v to ground through the resistor. (If 10k, I=0.33mA of wasted current, not significant in my opinion, higher resistor is less current through this path).
> 
> if pin 1 is not grounded, then pin1 will sit at about 3.3v, pulled high through the resistor (called pull-up resistor). Technically, it’s a voltage divider formed by the resistor and the input impedance of the chip pin1. I don’t know what this impedance is actually, but I assume it’s high enough that 100k resistor keeps it plenty close to 3.3v.
> 
> the same idea (pull-up or pull-down resistor) is used on the arachnid for pins 16-18 (program selection), and pin13 if you choose to add a switch to ground pin13 for fv-1’s stock internal patches.


Thanks @phi1 - I can’t wait to get mine built.


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## Paradox916

phi1 said:


> This is my 2nd Arachnid build, my first was the old version with the potentiometer to select patches.  This new version with the 8-way switch is much nicer.
> 
> Since PedalPCB hasn't released a dual eeprom board yet, I had to cobble together my own on perfboard.  If @PedalPCB does release a dual eeprom board, this would be the configuration I'd vote for, since the most obvious application is to use it on an Arachnid board, and I was able to keep it in a 125B.  It was a little tight having the switch at the top under the power jack, but doable.
> 
> I included shots of the dual Eeprom daughterboard, and a drawing of the layout.  Following info previously provided from PedalPCB, you can select Eeproms by manipulating Pin1.  Pin1 low (0v) is activated, Pin1 high (3.3v) is deactivated.  As he also noted, fliping the toggle switch doesn't automatically change programs, you have to move the 8-way selector switch before the fv-1 will recognize a program change.
> 
> It was tricky soldering the pin headers onto the bottom side of the perfboard, since I had to leave a space between the plastic and the perfobard to get the iron in there.  I just noticed that in the pictures that you can see I didn't get solder to fill all the way around on some of them (oops), but the connections all still registered with the multimeter.  I used a piece of white foam from Tayda's dip socket packaging to support the cantilevered part of the daughterboard.  I had to be careful about the order of soldering (8 way switch, then daughterboard, then mix pot).
> 
> For Bank A I used mostly spacialist reverb patches, with a code tweak on the shimmer so that it's only octave up. For the B side, it's a mix of PedalPCB patches (kaleidescope and sample hold), patches I found online, and some I wrote myself.  I used my dev board build with exterior eeprom socket to test all the patches and flash the A and B chips.
> 
> **EDIT** - the pdf on my original post had an error on the perfboard layout (see p_wats comment on 8/10/2020).  I marked up and reattached the pdf.


Nice work! That’s awesome!


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## Moltenmetalburn

heretop said:


> I am going to try this but with three eeprom, with this switch to switch between three eeprom. Will it work or any suggestion?
> View attachment 11542


Ive done 4 and 8 eeprom already, will work if space permits and your switch wiring is correct.


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## JamieJ

phi1 said:


> Hmm to be honest I’m not sure. I don’t have the unit pictured any more to look at for reference. If I recall right it was a tight squeeze just for the single row toggle. You could consider mounting the switch on the side, or below the rotary. In this case it’s be above the pcb, which toggle switches don’t quite fit in the same height of normally mounted pots. There’s some extra length on pot and rotary switch pins so you could make the pcb a bit higher, not sure if that would give you enough to fit the toggle. Or put a short shaft sw right next to the stomp. Seems dangerous, but I’ve done it and thought there wasn’t really any chance of stomping the switch.  Though that might not be ideal for you aesthetically.


I’m tempted to use a dpdt foot switch and use the other lugs to change a bi colour LED. Mostly just to economise on space and I don’t feel too happy about having a toggle switch need the main foot switch. I also want to use the mix mod on a switch that @jubal81 has written here about. So I’m planning on putting that where your toggle was on your build.


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## phi1

Bad news on the stomp idea, if you’re wanting it to instantly change programs. The program doesn’t change when you switch eeproms. The program only changes when pin 16, 17, or 18 change. As far as I can tell the fv-1 only fetched the eeprom data when it detects a change on those pins. So on my build, flipping the A/B switch does nothing until you turn the rotary. (Not sure if that’s a problem for what you wanted to do or not)


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## JamieJ

phi1 said:


> Bad news on the stomp idea, if you’re wanting it to instantly change programs. The program doesn’t change when you switch eeproms. The program only changes when pin 16, 17, or 18 change. As far as I can tell the fv-1 only fetched the eeprom data when it detects a change on those pins. So on my build, flipping the A/B switch does nothing until you turn the rotary. (Not sure if that’s a problem for what you wanted to do or not)


Yeah that’s fine by me. It’s mostly to make the best use of space knowing I’ll still have to use the rotary to change patch.


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## Moltenmetalburn

heretop said:


> Thanks for the reply! Are you using the 1p8t rotary switch to switch between eeprom? So you redesigned the board?


Yes 1p8T, no I didnt lay that one out as I preferred, four eeprom 2p4t and indictor lights. will probably fab that eventually. ive got 50 of the duals to off first lol.


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## Robert

phi1 said:


> Bad news on the stomp idea, if you’re wanting it to instantly change programs.



I have a theory (untested) on how you can instantly change programs when swapping to another EEPROM....


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## phi1

My theory would be to use an attiny to control pins 16, 17, and 18. Then you could pulse them 0-1 quickly to trigger the fv-1 to fetch eeprom. Hopefully there’s a more elegant way.

functionally, if just stomping to change eeprom could change the program, but not which patch # (1-8), and not the pots, that’s pretty limited function. So to me a fully integrated microcontroller system (pots, patch #, which eeprom) would be needed to get really useful stomp switch program changing (presets essentially).

 Now we may be into territory the daisy seed would handle more elegantly, though it seems enthusiasm has slowed on that front?


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## Robert

I think we can do it with the footswitch and no additional components. (edit: okay, maybe one resistor)

Like you said, it doesn't add a huge amount of functionality, but it'd seem more intuitive to me if flipping (or stomping) the switch actually had an immediate effect.

I haven't lost interest in the Daisy (or the FV-1 for that matter), I just haven't had time to tackle anything I want to actually do.


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## fig

Robert said:


> I just haven't had time to tackle anything I want to actually do.


I kinda noticed you are an extremely busy person.


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## Robert

I believe it can be done with a standard latching footswitch (or toggle switch), no microcontroller needed.

I'll have to dig out one of my FV-1 builds to test my theory.


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## JamieJ

Robert said:


> I believe it can be done with a standard latching footswitch (or toggle switch), no microcontroller needed.
> 
> I'll have to dig out one of my FV-1 builds to test my theory.


Looking forward to hearing your potential solution, all the parts has come in for my build.


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