Building an electronic giude (glorified music player)

[NSKL]

Hello everyone!

I've been asked by some friends who own a gallery whether I could design a cheap interactive guide for the visitors. Basically, we sat down and came up with the following:

The functionality will be like a typical music (mp3) player
ON/OFF switch,
Volume control
Small LCD to show track number
plus and minus buttons to select track
play/pause button
headphone jack

Visitors would get this device upon entering the gallery and each part of the gallery would correspond to a different "track" on the device, so that they can listen about various things in the gallery. We can load tracks in different languages to these devices to make it easier for international visitors.

We decided to include about 20, 5 minute tracks, for a total of about 100 minutes of sound.

I've been doing some preliminary research today, but I am still unsure how to get started. The important thing is to make this very cheap (for mass production) since they will be given away for free ideally (or for a very low cost). In addition, what audio format do you suggest? ogg, wav, mp3, anything else?

Any thoughts or pointers?
Thanks,
-NSKL

 

[mneary]

What's your price target, and what features would you give up to save cost?

1GB MP3 players are on ebay for CDN$15.98.

 

[NSKL]

Target cost is under 5 EURO, about $7-8 US. I can give up on 100 minutes of playback, cut it to about 60minutes. Also, this has to be no bigger than a credit card (thicker obviously). I already got a deal for the headphones at 0.17 EUR a piece!

Having said that, I was thinking an AVR processor (I only worked with AVRs so far), some extra memory and a bit of programming would do it. After a bit of research this is proving to be a bit complicated. As a first thing, AVRs need MIDI files AFAIK, but I can't record a tour guide's voice as a MIDI (or can I?) and stick it into the AVR.

Anyway, I need some help brainstorming ideas.
Thanks,
-NSKL

 

[mneary]

AVR processor might have enough horsepower alone. There's no limitation to the file format (but MIDI is out 'cause it's not voice). If you're decoding in software the big problem is obtaining or developing the code! I don't know if there are any free MP3 decoder source code available for AVR, but you should check around. There are MP3 decoder chips that'll add a little expense, but it'll be worth it if time to market is important.

I think that your biggest problem is in the packaging and user interface. Unless you're building millions the development cost will dominate your unit cost.

Not much savings cutting from 100min to 60min, especially since each extra language adds 60-100min of necessary storage. But if you had a programming connector (be clever and use the headphone jack?) then the correct language could be quickly substituted. But! Memory keeps getting bigger/cheaper anyway so this savings could disappear.

 

[NSKL]

Well, now that I had a bit of thought about it, maybe I can use .ogg files, and decode them in software in AVR (ogg is an open file format).

Regarding different languages part, it was decided NOT to load all the different languages on every unit, but make specific units with english, italian, french, etc.. and mark the packaging with a language sticker. Thus, each unit will hold only one language, around 100 minutes of speech.

I would just like to get your opinion on something. Do you think a memory chip, an AVR, and perhaps a MP3 decoder chip are all the important (major) components I will need for this project?

I found Daisy MP3 player here: Daisy_mp3 which looks like a very similar project, but it is too big/complicated/expensive for my needs. Still, I'm sure it will be a helpful resource.

Thanks for help!
-NSKL

 

[Nigel Goodwin]

I would just like to get your opinion on something. Do you think a memory chip, an AVR, and perhaps a MP3 decoder chip are all the important (major) components I will need for this project?

Yes, that's what you need (although any other processor would do).

 

[Mikebits]

How do you plan on packaging this thing? That may take a bite out of your budget. Also assembly cost etc.

 

[NSKL]

My job is to design this as cheap as I can, and later on other people will think about how to package it, etc... Packaging costs should all be well covered anyway because we will sell ad space on the information booklet that will come packaged with the electronic guide, which is good money.

Production is also not my worry. Apparently, the people I am making this for have contacts in China where they can get this manufactured. I need to provide them with a good design.

-NSKL

 

[NSKL]

Doing some more research, I'm now thinking that I can get away with using only an at89c51snd1c and a SD card reader (plus a screen, buttons and other connectors). Can someone confirm that an at89c51snd1c and some external memory would be enough to construct a simple MP3 player?

Alternatively, i found this: EDIT: Link does not work, just google DN2000 evergreen -its the first result.

However, I don't know how hard would it be to get one, pry it open and try to modify it (reverse engineer it). This might prove to be more difficult than building the whole thing from scratch, but that $8.50 price mark will be hard to beat!

Anyway, just collecting opinions if anyone wants to contribute.
Cheers,
-NSKL

 

[Nigel Goodwin]

Doing some more research, I'm now thinking that I can get away with using only an at89c51snd1c and a SD card reader (plus a screen, buttons and other connectors). Can someone confirm that an at89c51snd1c and some external memory would be enough to construct a simple MP3 player?

As it has an internal MP3 decoder it should be capable of the job, presumably the datasheet shows how to make an MP3 player with it?.