Need Suggestions For Upcoming PIC Project

[Tim Daneliuk]

I want to build something that allows me to record the output of an
electret microphone onto a USB memory stick. Ideally, I'd like to be
able to record mono/stereo at various quality settings, say, voice audio
all the way to full music quality up to the limit of the mp3 format.

I am quite familiar with the analog end of this problem, and have done
a number of medium complexity PIC projects over the years. But ... I
have a few questions:

1) Is there are PIC part that can do the A/D at the appropriate rates
for the desired audio quality settings? Is there a better part than
a PIC for this?

2) Once I have the audio in memory as a bitstream, are there open source
routines to create mp3 format files?

3) Is there a standard hardware/software library for interfacing with
a USB memory stick and dealing with its file system.

Effectively, what I want is a small, low power replacement for a
cassette recorder.

TIA,

 

[Michael Lange]

Hi Tim,

I want to build something that allows me to record the output of an
electret microphone onto a USB memory stick. Ideally, I'd like to be
able to record mono/stereo at various quality settings, say, voice audio
all the way to full music quality up to the limit of the mp3 format.

I assume, this is a hobbyist project ... (otherwise you can by an USB
stick with mp3 recorder for a small amount)

I am quite familiar with the analog end of this problem, and have done
a number of medium complexity PIC projects over the years. But ... I
have a few questions:

1) Is there are PIC part that can do the A/D at the appropriate rates
for the desired audio quality settings? Is there a better part than
a PIC for this?

You don't specify the requirements, but I have no experiences about the
conversation time of the PICs too. You are familiar with the PICs, so I
suggest, read the manuals and/or write a simple example.

2) Once I have the audio in memory as a bitstream, are there open source
routines to create mp3 format files?

I don't know. What's on google?

3) Is there a standard hardware/software library for interfacing with
a USB memory stick and dealing with its file system.

Because there are a great conceptional difference between USB and other
serial interfaces, there is no way. USB memory sticks and PICs are only
available as USB-slaves and can not act as an USB-Host-Device (like
USB-togo).

Effectively, what I want is a small, low power replacement for a
cassette recorder.

If you like to build this with a PIC, think about a CF or SD card as
storage, and use a small card reader (like a plug) for connet to PC.

Michael

 

[ChadMan]

I think the latest line of PIC parts would do the required freqeuncy of
conversion but I don't think the resolution will be adequate for audio
quality, if you use the standard 16-bit, 41KHz sampling on the ADC as a
template. For stereo, you need to sample two channels. You may be better
off using a dedicated audio CODEC.

How about the DSP family of dsPIC?

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=75