So I was wondering if anyone would be willing to give this PCB of mine a look over. It’s my first board, so I’m sure there are a few things that can be done better. I’m especially concerned with EMI, since I’m using a firmware USB driver, and it’s been pretty sensitive to EMI while prototyping. It’s also got an option to communicate over I2C, but I’ve never had transmission problems with that…
I did the layout in the open-source KiCad, which outputs .sch and .brd files, but I’m not sure how compatible those file are with other programs, so I’ve also provided links to .svg vector images of them; with the PCB layout, you can move the layers to uncover the +5v fills, etc.
All the files can be found here, all starting with “General V1 PCB…” :
About my project - I’m building a device that lets you play Guitar Hero with a regular guitar. Basically, you attach wires to the strings and frets of a guitar, then use the contacts between the frets and the strings as switches to tell a microcontroller what notes are being held on the guitar neck. The microcontroller then sends out signals emulating a Guitar Hero controller, either a USB or a Wii controller.
Anyhow, thanks to anyone for looking over these files!
I noticed that you made a 5v+ plane on the top of the board. You really don’t need this for anything. Simply run a trace to the places on the board you need to get 5V+ to. Also, the resistors on the right side of the board don’t line up with the pins on the micros. This really won’t change much, but it will look better. I am also wondering why you are using such a giant crystal package? As for you EMI issuse I would like to see you opto isolate the inputs from the guitar and pick.
I had no idea that something like an opto-isolater existed. I’m also currently using a giant crystal package because I don’t know any better. Basically, I’ve got some laying around, and I’m not overly concerned with space requirements on this system at the moment. I’m going to be making a SMD version of this board soon, though, so I’ll probably switch to a crystal/capacitor solution. It’s just that finding new parts when you don’t know how to look for them on DigiKey is kinda a pain…
Thanks a bunch! It always takes me like 2 hours to make a digi-key order, just since I have no idea what the connectors I want are actually called, or how to just order a cheap, average diode…So many options!
Is there anyway you can PDF the board and schematics? Or make a gerber export of the board for review (if you are willing to release them)? I’m having issues with both Inkscape and Illustrator understanding the SVG.
In a similar but different vein, you may be interested in this little OpenCV project I did awhile back:
No need to use an external oscillator, usually its cheaper and smaller to use the oscillator in the microcontroller with just a crystal.
The Mega8 is end of life. Make sure everything you do works with its near-drop-in replacement, the Mega88, as the Mega8 may be harder and harder to find.