[sdiy] Serial EPROM, sample playback

[wayfar]

A few things, first don't use the 16f84, the 18 arcitecture is better 
and includes hardware multiplyer instructions, even better check out a 
dspic. The prices are all comparable in the under $6 or so range per se, 
so do yourself a favor and get up on the latest chips Microchip has 
avaliable.

Battery backed sram would be a cheap but small way to store your 
samples, if you want longevity use flash instead of eeprom. Nvram is 
avaliable but expensive and has a limited write lifespan. Fram from 
ramtron is similar.

There are dip versions of most all flash chips 4megabit and under, check 
out the amd29fseries, if your looking at the larger sst or st chips then 
maby you should think about using a cf card or sd.

If you have no programmer check out a Microchip ICD2, to program and 
debug your pic projects, it's very cheap for a programmer and you get a 
in circuit debugger to boot, they are around $150.00 for the usb version.

If your on a tight budget there are icd2 cones on ebay.

Don't use a shift register on a parallel eeprom, get a better micro to 
use and use the extra lines.

Think about it this way, someday you will eventually upgrade to more 
capable chips, with more advanced features whether it's microchip or one 
of the other popular chip makers, why not get into them today rather 
than tomorrow, (especially considering that they are priced all under 
$10 or so)? You will be r0king harder with the latest technology.

Another thing about the dac, there are SPI interface stereo dacs, 
avaliable from microchip, these chips have an enable line so you can use 
it on the same buss as your other SPI peripherals provided that you take 
care to avoid buss conflicts.

Cheers,
x|k

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