[OSM-talk] South Downs Way

[Robert Scott]

On Saturday 08 July 2006 21:50, Robert Scott wrote:
> The PICs with USB support are clients, not hosts sadly. And they only have
> one port, I think.
>
> So you'd have to implement the whole of USB (ok, just the subset required
> for mass storage and garmin) in software. That'll be hard to fit in the
> memory of a small PIC.
>
> And also you'd have to implement a filesystem, probably FAT16, if you
> wanted anything more than a single long tracklog.
>
> I fear that this would really need a microcontroller big enough to have an
> operating system to do that for you.

Replying to myself here, but I didn't realise that MMC cards use an SPI 
interface - so writing to it from a PIC is easy. The only painful bit is, 
again, the filesystem. But you could always use your own very naive 
filesystem which just started a new track every 512kB or so.

I was thinking of a more powerful system so that you would be able to gzip the 
data onto the storage device, but there's no reason you can't implement gzip 
(or an even simpler stream compression algorithm) on a PIC. Memory would 
probably be the constraint on the compression ratio.

Combine a £2 PIC with a (don't know the price. ~£30 I guess) OEM sirfstar III 
UART unit and you might have something very useful.


robert.