[sdiy] Serial EPROM, sample playback

[Seb Francis]

if you are low on pins I would suggest using a DAC with SPI interface.  
if you are already using something with SPI then you will need only 1 
extra chip select pin for the DAC.  SPI's pretty easy to do with a PIC 
and with a 20MHz PIC you can run the SPI bus up to 5MHz which should be 
plenty fast enough.

I can't suggest a specific DAC because I don't know your requirements .. 
bit depth, sampling frequency, accuracy, etc.

seb


Johannes Öberg wrote:

> Hi list!
>
> I'm making another sample-playback thingy. This time it's longer and 
> reprogrammable (>=20 times) samples and better quality (>=3 secs, 
> >=6bit 15khz or equiv.). It's a PIC 16F84 in the middle, and 
> everything will run on batteries.
>
> What would be the best way to store the sample? I'm considering an SPI 
> Flash EPROM, but it seems quite cumbersome to interface them with 
> bitbanging. The I2C ones seems even worse. What's worse is I can only 
> find surface-mount flash eproms. Therefor the programming would have 
> to be in-circuit, and adding a PC interface on the PIC seems very 
> difficult, not to mention it eats PIC legs. But maybe I'm wrong?
>
> What simple diy SPI Flash programmers exists? Preferably with DOS/Win 
> software.
>
> What's done already that I should look at? How about trying to 
> interface a parallell (E)EPROM with some help from a shiftregister? 
> Would this eat alot of power?
>
> Also, would perhaps I2C be better? It does seem terrible for 
> bitbanging, especially since I lack proper test equipment (I only have 
> a slow scope and a DMM).
>
> I'm also concerned about the DAC. Since I'm low on free PIC pins, 
> Roman Black's 1.5 bit DAC seems to be the most suitable. Anybody have 
> any other suggestions I should look at?
>
> Any tips welcome!
> /Johannes