Arachnid - Dual Eeprom

[adolfo]

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 !!!

 

[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.

 

[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).

 

[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.

 

[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.

 

[Sasan]

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...)

 

[JamieJ]

This is amazing. I would happily buy one too.

 

[Moltenmetalburn]

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.

 

[Moltenmetalburn]

This is amazing. I would happily buy one too.

PM me for contact info.

 

[Bricksnbeatles]

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.

 

[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.

 

[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.

 

[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?

 

[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.

 

[JamieJ]

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.

 

[Paradox916]

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!

 

[Moltenmetalburn]

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.

 

[JamieJ]

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.

 

[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)

 

[JamieJ]

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.