Title: Digital audio effects processor (Guitar stomp box)
Post by: Catmacey on April 30, 2014, 02:16:23 am
Post by: Catmacey on April 30, 2014, 02:16:23 am
Here's another "Guitar stomp box" project...
This one combines a Chipkit DP32 (PIC32MX) with an Open music labs Stomp Shield to sample audio, mess with it and squirt it back out at 44Khz.
It uses the built-in 10bit ADC for input and two 8bit PWM DACs to provide a 16bit output. It's a clever solution to use two "small" high speed PWMs mixed like that, thank you Open Music Labs.
So far I've have Delay, Bit-crush, Tremolo and Flanger running. All of which can be run at the same time with headroom for more.
I've written more here http://http://catmacey.wordpress.com/2014/04/30/introducing-the-chipstomp/ and will be publishing all code and schematics once I have it all tidied up - yeah they all say that don't they...
The PCBs are done and are currently with Dirty PCB.
Title: Re: Digital audio effects processor (Guitar stomp box)
Post by: Catmacey on April 30, 2014, 03:08:55 pm
Post by: Catmacey on April 30, 2014, 03:08:55 pm
Updates:
1. I changed the title of this thread to include "(Guitar stomp box)" as I realised it sounded a bit grand and misleading as it was.
2. Just received notification that the boards are back from the fab. Excellent.
I must say I'm really liking the Dirty PCB experience so far, especially the notifications.
1. I changed the title of this thread to include "(Guitar stomp box)" as I realised it sounded a bit grand and misleading as it was.
2. Just received notification that the boards are back from the fab. Excellent.
I must say I'm really liking the Dirty PCB experience so far, especially the notifications.
Title: Re: Digital audio effects processor (Guitar stomp box)
Post by: Catmacey on May 16, 2014, 11:50:18 am
Post by: Catmacey on May 16, 2014, 11:50:18 am
I just got the boards back from DirtyPCBs today and they look very nice.
On a couple of boards I quickly checked the silk is sharp and clean, no blotches.
The black solder mask is very cool but I might choose a different colour for a first prototype next time as makes it very hard to spot the traces underneath, that's good for a final version but might actually be a hinderance in a prototype where I typically have to make alterations...
Here's a quick photo from my phone.
I'll take a better picture with my camera when I get them home. I'm hoping that I'll have a chance to start building one up this weekend.
Here's a link to a hi-rez photo (1.4Mb) (http://http://catmacey.files.wordpress.com/2014/05/img_0692.jpg) if you're interested.
On a couple of boards I quickly checked the silk is sharp and clean, no blotches.
The black solder mask is very cool but I might choose a different colour for a first prototype next time as makes it very hard to spot the traces underneath, that's good for a final version but might actually be a hinderance in a prototype where I typically have to make alterations...
Here's a quick photo from my phone.
I'll take a better picture with my camera when I get them home. I'm hoping that I'll have a chance to start building one up this weekend.
Here's a link to a hi-rez photo (1.4Mb) (http://http://catmacey.files.wordpress.com/2014/05/img_0692.jpg) if you're interested.
Title: Re: Digital audio effects processor (Guitar stomp box)
Post by: Catmacey on May 29, 2014, 02:44:31 pm
Post by: Catmacey on May 29, 2014, 02:44:31 pm
I eventually found some time to start assembling my Chipstomp. The PCB is perfect, the only problem being a mistake I made in laying out the PIC's ICSP clock line which I managed to have connected to completely the wrong pin...
That was easily fixed with a small bodge wire, but I'm defintely sure now that the black solder mask is not a good idea for an early prototype. It's just too hard to spot the tracks underneath, even with a bright light shining from the other side.
Here's a photo of where I am so far with the build.
I've got the digital side of things up and running after a bit of messing around with the Chipkit bootloader and Microchip's free compiler limitations. The crux of the problem being that
my buttons are pulled high - pulled low by the putton press - whereas the Chipkit DP32 is the other way round. This mean't the the bootloader was always being activated on reset. The fix was to change a single value in the bootloader board config file and rebuild the project. The hassle is that the bootloader project needs to be compiled with -s optimisation and mips16. These options are not available in the free xc32 compiler, so after a bit of messing around I settled on the simplest solution which was to use the 60 day free trial of the pro version.
If you interested, my intention is to publish the full circuit and source code so as a starting point my Eagle CAD project files (http://https://github.com/Catmacey/ChipStomp) are available on Github. As I find more time I'll be tidying up, revising and publishing the rest.
That was easily fixed with a small bodge wire, but I'm defintely sure now that the black solder mask is not a good idea for an early prototype. It's just too hard to spot the tracks underneath, even with a bright light shining from the other side.
Here's a photo of where I am so far with the build.
I've got the digital side of things up and running after a bit of messing around with the Chipkit bootloader and Microchip's free compiler limitations. The crux of the problem being that
my buttons are pulled high - pulled low by the putton press - whereas the Chipkit DP32 is the other way round. This mean't the the bootloader was always being activated on reset. The fix was to change a single value in the bootloader board config file and rebuild the project. The hassle is that the bootloader project needs to be compiled with -s optimisation and mips16. These options are not available in the free xc32 compiler, so after a bit of messing around I settled on the simplest solution which was to use the 60 day free trial of the pro version.
If you interested, my intention is to publish the full circuit and source code so as a starting point my Eagle CAD project files (http://https://github.com/Catmacey/ChipStomp) are available on Github. As I find more time I'll be tidying up, revising and publishing the rest.
Title: Re: Digital audio effects processor (Guitar stomp box)
Post by: kasbah on June 23, 2014, 08:34:06 pm
Post by: kasbah on June 23, 2014, 08:34:06 pm
Cool project! Shame about Microchip's crippleware.
Title: Re: Digital audio effects processor (Guitar stomp box)
Post by: Catmacey on September 28, 2014, 07:26:47 pm
Post by: Catmacey on September 28, 2014, 07:26:47 pm
Just a quick update to this project log.
After a lot of tidying up I've released version 1 of the C++(Chipkit/Arduino) code for this project up on GitHub.
You can also find the Eagle Schematics and PCB Layout up there too.
As it stand the device has the following effects;
Flanger
Tremolo
Pitch Shifter
Delay/Echo
Bitcrusher
Any or all of which can be active at the same time.
https://github.com/Catmacey/ChipStomp/ (https://github.com/Catmacey/ChipStomp/)
After a lot of tidying up I've released version 1 of the C++(Chipkit/Arduino) code for this project up on GitHub.
You can also find the Eagle Schematics and PCB Layout up there too.
As it stand the device has the following effects;
Flanger
Tremolo
Pitch Shifter
Delay/Echo
Bitcrusher
Any or all of which can be active at the same time.
https://github.com/Catmacey/ChipStomp/ (https://github.com/Catmacey/ChipStomp/)