Re: [avrdude-dev] USBasp improvements

[Wouter van Gulik]

Jurgis Brigmanis wrote:
> Hello!
>
> I'm about to improve USBasp - add software control for ISP SCK speed 
> (so I could place USBasp in a sealed case and stop worry about "Slow 
> SCK" jumper). In fact, i've already (sort of) implemented that, just 
> not ready to submit patches yet.
>
> I was planning to use Avrdude's -B, bitclock command line switch for 
> that (IMHO it fits), but here's a problem: AVR doesn't have very much 
> control on hardware ISP speeds - just by factor of 2 - 750kHz, 375kHz, 
> 187.5kHz ...
>
> Unfortunately -B means bit clock period not frequency, and 375kHz for 
> example, results in 2.66666(6)us period.
>
> Suggestions?
Well the STK500 is not exact either. It also rounds somewhere somehow. 
So for stk500 users it would not be a big surprise.

HTH,

Wouter