I'm starting to brainstorm for an MP3 PC in my car. Most people take the complex route, and hook up fancy LCD displays and touchscreens and so forth. I'm not interested in any of that. I want the absolute simplest setup possible. I've already got all the hardware I'll need for the PC, nothing fancy, but adequate. Anyways, the real dilemma is in controlling the computer. I don't want to bother with touchscreens or any sort of display for that matter. That would involve spending money, which I want to avoid. I pretty much want to cobble together a simple 5 button control panel that's hooked directly to a serial (or parallel, I have no idea, that's why I'm asking) port. I should be able to write a simple VB program (pending a crash course in serial interface) that'll play the MP3s. Basically, has anyone done this? Any links to project logs? Advice? How should I go about constructing the control unit? I figured SPST momentary switches, but I don't know a whole lot about hooking custom stuff up to ports, so I guess I'd need to know about this. What else should I consider?
Try and get hold of the past couple of issues of PC Plus magazine; they're running a mini-series (about 5 issues I think) on making programs to use the serial and parallel ports. I think they're in VB in .NET but they should be all you need if you can code the rest of the program. If you want I'll scan the pages in for you but only if I get permission from a moderator to put the images on here since I'm not sure of any copyright issues.
How about just cutting up a keyboard? Have your mp3 player as part of the boot-up on your PC. Take the guts out of a keyboard and slim it down to what you want, and assign those keys to the functions of your mp3 player util. Just a thought.
I've been looking at this. The problem is that every keyboard I've ripped apart has had some bizzare maze of traces and overlapping switch pads. Unless I could figure out how to completly eliminate all that foolishness and simply use the keyboard controller with my own 5 buttons, I'd have to stick to serial
I hacked up a keyboard for my MP3 player. The easiest thing to do is to dissemble the keyboard until you have the PCB infront of you. Plug it into a PC and fire it up into DOS. Now all you have to do is short out on the connector, where the keyboard mat plugged in, with a small piece of wire until you get the characters you want.
Or you could apply this principal to a USB number pad, its more expensive but easier to get the charicters.
Argh... messy! I have seen keyboards that you can buy for laptops which consist of only the numpad. There are ones for ps/2 and usb. Here is a usb one I found on maplin. All your code will have to do is detect key presses on the keypad as if they were on the keyboard. If your keen on using a matrix keypad and hooking it up to the parallel port instead, give me a shout and I can help you with that. I just recently recoded some keypad code for a matrix type keypad attached to a printer port, but it's in c++ tho. If you're coding the mp3 decoding/playing software yourself (and not using winamp), a great library to use is BASS and it works for VB (not sure about .NET), VC++ and Delphi.
I would still go for the hacked up keyboard as its the cheapest option. Instead of writing your own code, why not just use winamp or similar. If your not having a display why write your own code when winamp 2.8ish is nice and stable and has keyboard commands. Also consider bashing together a smaller version of the OS you are going to use, makes for faster booting. See http://www.wimborne.org/richard/shrinkingwindows/ for details. Also have a look at http://www.mp3projects.com/ for some inspiration
I just ripped apart an old keyboard and mapped out all the points that correspond to the keys I need to control Winamp. It took a whole lotta probing, but now I've got all the information I need to adapt a keyboard into the controller for my MP3 player. I guess I'll have to start cooking up a case design so I can get my hardware into the car now.
