"building" my own flash portable mp3 player...

First post and first thread here!

Okay, so, this is something I've scoured the web for but to no avail.

Here's the situation!

I've built my own pc, no biggie. I fully understand what a leap building a portable mp3 player from that would be. I know java, but I wouldn't consider myself a coder, that is, my job is and never has been that of a programmer, its merely something I'm interested in, and apart from a silly applet or application or two, I've not programmed a full application.

Okay, now, I've got a whole bunch of questions, firstly, how hard?

Secondly, what does the PCB board do. Now, I know you're probably thinking "this guy hasn't got a clue, best tell him to give up" but I'd really appreciate answers just for curiosity's sake. I've got a schematic and PCB designing program, I've found a good company that will manufacture one PCB board for me. The thing is, what does the circuitry need to do? Just link up the ICs? What about capacitors? Obviously I realise I also need to use the circuitry to ground stuff and actually supply power to stuff!

Okay, ICs, I've found a couple of MP3 decoding chips, the thing is, is there anywhere that reviews this stuff? Also, I've looked at the datasheets, but as I'm sure you are aware its important I know the size of the things and so forth before I even start to draw up the PCB schematics.

Basically, what do I need? What ICs do I need? Is it a case of connecting them up? Am I being incredibly naive? I honestly don't even know how to find the stuff I need.

The datasheets do tell me alot of what goes to what, and I suppose I could get all the chips from the one company, hopefully.

Also, lets say I've soldered everything somehow and all is okay, then what? Do these things have some functionality without me doing anything else? I mean, forgetting about input devices and whatnot, well, a play button, what exactly 'tells' the flash card controller to send the stuff to the mp3 decoder and then out to the bit that converts it into an analog signal and sends it off to the headphone jack?

Don't laugh, I may sound like a fish out of water... or a hedgehog shoved in the deep end... but humour me, cos I'd really appreciate some answers!

Thanks, any help MOST appreciated!

First of all, you would benefit from a decent course in electronics including semiconductors and microelectronics.

That's where you would learn that a Printed Circuit Board (PCB) is a copper-clad plate of insulation (in its simplest form) in which much of teh copper is etched away to form wire-like paths between points where electronic components are mounted. It acts both as a scaffold for the electronics and the wiring necessary to create the circuits.

Also, you would learn about the voltages you would need to supply, and perhaps the various components you would need.

Off the top of my head you will need:

- Flash memory
- I/O control circuitry, including whatever communication protocol you will need to interface with the computer or whatever will provide you with the music files.
- MP3 format decoder
- Audio amp (with DSP if you want any kind of effects, like an equalizer).
- User interface, whether it be just buttons, or some sort of display.

Chances are, it will be big-- the size of a portable CD player or better.

This is a good exercise/project for an aspiring electrical engineer, but I think you have a long way to go yet.

Thought so, thanks anyway! Most likely I'll never have neither the time nor the money to go on such a course, oh well!

Just curious though, why would one need to go on a course to find out about the voltages required, when the datasheets have all this information for each chip?

Also, enlighten me... why is it more complicated than a) buying all the components and then b) designing the pcb so they're simply all connected up and then having the manufacturer print it for me? I mean, where do things get complicated?

Ooh, just like to add, the thing is, back in the seventies and eighties, hobbiests were doing this sort of thing, albeit for actual machines most people would consider a computer, and these people were the likes of Steve Jobs and others who did not have the education that you say I need to do this... I mean, thats where I got the idea that there's a small chance this is possible... right now, to me, it sounds simple enough, the problems are finding which chips to use (ie. which ones are good) and the dimensions of them, but I know it must be more complicated than simply joining the dots on a CAD program otherwise everyone would be doing it... right now I am yet to understand where it gets complex.

Well, there are different classes of microcircuits that operate on different voltage levels-- 5vdc, 3.3vdc, even a few 1.7vdc for computers. You would ahve to decide which components are right for your purposes, whether they will work with each other and still allow some battery life. If the one decoder you need is a 3.3v, but the only amp you can use needs 5v to run, then what do you do?

The real complication lies in designing the PCB. If you are running a 16bit parallel bus, say, from the I/O to the Flash, each of the runs on the PCB for that bus has to be the same length with some accuracy, otherwise you'll have a data mismatch problem which will mean you'll have to slow the data bus clocking speed... you are going to need a certain amount of clock speed in order to get real-time decoding and playback.

Also, you have to watch the width of the individual runs as well as the distance between them. This isn't as important on the macro scale you would be using (as opposed to what computer motherboard designers have to deal with... and some of those smaller MP3 player builders have the same issues), but there are issues there.

Then there's the troubleshooting that comes after your build-- if you don't know how the stuff works, you'll be playing guessing games trying to figure out what isn't working right.

Mind you, I'm not trying to dissuade you, just telling you what you can expect out of the venture.

Thanks! Nah, I've always known I couldn't really do this, the thing is there are so little resources on the net, I expected tutorials on simple PCB circuits and so forth, just like one gets with everything else. Well, anyhoo, thanks again! P.S. if anyone has any links to guides to PCB stuff I'd appreciate it, not neccesarily advanced stuff either.

Okay, update, portable MP3 player... a no no! As I've said before. But, the thing is, I've got a 3.3v flash card, a couple in fact... how plausible is a flash card reader? It could be USB, ATA, or whatever the floppy thingy uses, whichever is easiest... any of them would give me the ability to put one in one of my drive bays (floppy or the bigger one for CDs, whatever its called!).

I'd need some kinda I/O ics, right? And some other stuff...

To be honest, I really just want to make something, a flash card reader also sounds a wee bit advanced... so, what I'm asking for here is if anyone knows a decent site which will teach me the basics and beyond that is aimed at simple projects... believe me, I've searched, and am bewildered I haven't come up with anything, nothing at all...

Here's a starting point: Articles about "Electricity" Bill Beaty's explanations on the basics of electricity are simple, easy to digest, and above all avoid handing out common misconceptions that are spread as gospel elswhere. Continuing in that vein, Bill Beaty's "Electricity" Misconceptions page. I especially enjoy his article on how transistors work.

NEETS on eBay Those CDs have the basics of electronics in an easily digestible form... it's the basis of what the US Navy teaches all Sailors who need electrical knowledge for their jobs.

Super! Glad I found this forum, never even heard of the website before, but doing a search specifically to ask these questions and I found this place, super! Thanks again

Buy a breadboard. Build it on this before you consider getting a pcb printed. Try and buy more then one PCB, as there is a significant chance you will screw up one or more.

If you are a complete n00b to this. consider creating a simple 555 astable, bi stable, and a divide by 18 chip, to create a random output generator. IE: two timing devices and a divide by 18 chip to create a couple of flashing LED's which then stop on one random LED.

Electronics can be hard to get to grips with, i know, because i suck at it. I'm currently struggling to make a simple fna controller with pentiometers, transistors and resistors, and thats all without a single chip. I wouldn;t reccommend starting in the deep end, unless you have a step by step guide explaining what everything does.

Would like to add tho, that misconceptions bit, I am a bit concerned where they're teaching kids most of those misconceptions... I can understand some of them being taught to younger minds for simplicity's sake, but most of the misconceptions mentioned there surely kids should have gotten rid of by their mid-teens at the latest? Bit concerned about how our education system must have deteriorated... I honestly had no idea! High-level analogies of things are perfectly okay, but I get the impression kids today are being taught some very skewed views on things...

Thanks butmunch. I find it a little odd that not one single enthusiast has made a step by step guide though, I never expected it to be plug in and play purely because there isn't a market for those sorts of products, unlike with PCs... but I am bewildered by the lack of tutorials on this sort of thing.

Unfortunately I don't have a whole lot of cash to spare on experimenting, I'll look into your suggesting though.

Thanks again!

Oh, it's not expensive, you can pick up basic electronic components for cents/pence. Breadboard might be a couple of quid though.
I have the advantage, I can use my schools equipment, and I can blow up capacitors for free (not that i've actually doen that yet).