DIY octa switch thingy

[1878]

Hello Everyone...

I've been looking at an Octa Switch type thing recently, but I've got some concerns.

1. I have about 20 (give or take a few) different effects that I use regularly but the Octa Switch only has room for 8.
2. I'd prefer more than 8 presets.
3. I'd probably have my volume pedal 'always on' just before the delay.
4. I'd like a mute/tuner out.

So ideally, I'd have between 12-16 loops with each one being fed into 2x12 DIP switches giving me room for 24 effects. I'd also include switchable input/output buffers.

I don't need the LED's telling me which effect is assigned to the loop I'm using.

Although it would be worth the time & effort to build my own I'm wondering, 'is it feasible ??' I've had a quick look at the article on Geofex and unfortunately for me it's gone straight over my head. Has anyone built the switching system using the 74C373 and if so, is there a schematic ?? I don't have the knowledge base to fill in gaps at the moment

I understand this is a mammoth task, but it's one I'm willing to tackle with some help.

Thanks in advance.

[defaced]

Yes it's feasible, but if it were me, I'd probably do it with a micro controller (MCU).  
I have built a project that uses RG's switching, I have also built a project that uses a MCU to control the logic.  If the turkey day shootout hadn't had a "no digital" rule, I would have used a MCU for the logic.  
The schematic for the switching is at the bottom of the schematic: http://www.diystompboxes.com/smfforum/index.php?topic=99142.msg879595#msg879595
It works well, but your project is significantly more complicated than switching between four settings.  

Other random thoughts:
-For something that large, you might run into fan out problems with the logic chip driving the various relay drivers.
-Someone who has been around the block might know a trick to gang two 737s together to get 16 outputs.  This would get around the need for a MCU (and eliminate the learning curve/cost that is involved with getting into programming MCUs)
-Planning the power for this will be fun.  I won't be surprised if you need to go the route of a transformer and mains wiring.  The number of relays you plan to drive at one time will be the driving force here.  
-If you break down how you use your pedals, you might find you can make an octa switch work, it'll just require some creative routing and arrangements.  
-There might be some other custom switching solutions that do what you want already.  

[1878]

I thought there would be some problems involved !!

What micro controllers/software do you suggest ?? I was given an Arduino Mega 2560 for Christmas which is still in it's packaging but I wouldn't have a clue if this would be up to the task or not.

[defaced]

I know squat about Arduino, so take what I say with a very large grain of salt, but that module certainly has enough I/Os to do what you want.  It'll probably be like using a bulldozer to build a sand castle, but that's better than using a plastic toy shovel to build a real castle. 

[stirfoo]

I started down this rabbit hole about a month and a half ago. If I could give one bit of advice it would be, start small. Input -> tuner out -> one loop -> output.

I decided to "go large" immediately. Micro-controlled, 10 loops, left/right out, two amp control outs. I've almost got it finished but it's been, as you suggested, a monumental task.

I studied the octa switch for a bit. It looked quite feasible, but it seemed too limiting for my tastes.

[alparent]

Arduino is more then enough.
Your mega might be overkill.....but when your done with programing you'll just dump that code on a smaller chip.
Tayda as ATTINY for like 1$.

Read up on the Arduino site and you'll get what I'm saying.

[stirfoo]

Depending on how far you'll want to ultimately go with this, there may be many I/O lines required of the uC.


The relays will eat one each.

Input switches may eat one each. There is the possibility of using a voltage divider matrix to read them though. I didn't look too deep into this because I couldn't determine how readily simultaneous stomps could be read.

If you incorporate presets, each will need an LED pin to show which is active.

A 7 segment display (for bank display) will require 4, 5, or 7 pins depending on how you implement it.

Mini DIP switch for configuration. 4 lines, 8, etc.


My looper uses MCP23017 port expanders. These have 16 I/O lines. Up to 8 of these can be used while requiring only two pins on the uC. It also uses a mini DIP switch for configuration. That's 4 more input lines. I still have to add a post-relay mute circuit. That's one more output line. In its current form, 55 I/O lines are required. But you have to keep in mind this is my first attempt.  I could definitely reduce this count.

Also, I'm going to add a Bluetooth interface so I can save/load presets from my phone.    I think that's at least two more lines.

Like alparent said, your Arduino should be more than enough to get started. I cut my teeth on an Arduino Uno. But again, start simple!

[1878]

Thanks for the replies.

I've never used Arduino previously, but it seems quite logical. I did a bit of reading up on it last night but couldn't pin point exactly what I needed. I read about libraries of commands. Are there audio libraries knocking about or do I have to start from scratch ?

Also, the Octa Switch uses DIP switches to assign effects to a loop. Am I right in thinking Arduino could do this for me or is that a whole barrel of nonsense to be traveling towards. I don't mind having banks of DIP switches, but it would obviously be a lot tidier if the chip does this for me.

#stirfoo 'If you incorporate presets, each will need an LED pin to show which is active.'

Do you mean an LED for which loop or for which effects are assigned to that loop ? I'd only require LED indicators for which loop is active.

Thanks again.

[R.G.]

There is a whole lot of Very Useful Information on the general topic of Octa Thingies at Geofex in the "programmable footswitcher" articles.

Including the idea that once you can run a relay from a logic-based controller, the rest is all A Simple Matter Of Programming - or ASMOP as I contracted it.

[1878]

Right ok. I need to get my starting point correct before going any further. Feel free to tell me if I'm & where I'm going wrong. It's been an informative 24 hrs or so !!

1. I can program my Arduino to instruct relays to switch different loops in & out of the signal chain.
2. It seems I can also program which loops to switch, doing away with DIP switches.
3. Rather than having 12 footswitches, I can have 6 or less, but have 2 or more banks.

I've seen other things like LCD displays, joysticks, switches etc but they can wait for now. I just need to know if it's possible to achieve the three points above. I'd still need the option of 20ish loops, but I'm happy to reduce the number of switches if the bank idea will work.

Thanks again.

[Pete.M]

I've been thinking about this same topic. An Arduino would certainly be up to the task. It's got a huge user community, and plenty of sample code available.  You could use pretty much as many stacked 74HC595 shift registers as you want on a single "port" of the 'duino, for instance 3 chained together would give you 24 digital outputs, and you would still have room for more IO. A starter kit like this one from http://adafruit.com/products/68, will get you going nicely.

I use the Arduino Uno R3 for prototyping, and then I move the code to a smaller/cheaper ATTINY series (ATTiny2313) like alparent mentioned.

pete.m

[stirfoo]

Do you mean an LED for which loop or for which effects are assigned to that loop ? I'd only require LED indicators for which loop is active.

Well, the loop status LEDs simply mirror their respective relay states so you don't need extra pins for these. They can draw power directly from the 9v current that's powering the relay. Or, off the 5v signal that tells the relay to turn on. I use the latter.

I can have up to 80 presets. 10 switches * 8 banks. So 10 LEDS that the uC toggles depending on which preset is active. The bank is shown by a single 7 segment display.

There are probably 101 ways to do this.

Check this one out. I found it in a carl martin thread here on diystompboxes.

http://dl.dropbox.com/u/15275178/SwitchNLopp.pdf

It's done with hardware logic. No uC. But still, it's limiting. You only get 10 presets and to program them you have to bend over with a tiny screwdriver to flip the switches. With a uC you can have as many presets as you have memory and do all the programming with your feet. 

The DIP switches on the carl martin are like memory banks. One switch (bit) per relay. I just store those bits in the uC's memory instead of hardware switches.

[MoltenVoltage]

If you want to a programmable switcher that is expandable, you can use a number of our 9 switches modules and control it with any MIDI controller:
http://www.pedalsync.com/documentation/PedalSync_MV-62_9_Switches_Datasheet.pdf

Then you can store and recall 128 presets.

The module was designed specificially for this task.