Re: [avrdude-dev] USBasp improvements

[Jurgis Brigmanis]

Sorry for long delay. Here are patches.

Patches are against latest released USBasp firmware version
(2007-10-23) and Avrdude's CVS version (as of 29.03.2008).

Software control over SCK frequency from 1.5 MHz down to 500 Hz.

Bitclock period, specified using -B switch, is rounded to closest
available frequency:
less than 0.5 or none - default speed (jumper setting)
0.5 - 1.0 -> 1.5 MHz
1.0 - 2.0 -> 750 kHz
2.0 - 4.0 -> 375 kHz
4.0 - 8.0 -> 187.5 kHz
8.0 - 20.96 -> 93.75 kHz
20.96 - 46.88 -> 32 kHz
46.88 - 93.75 -> 16 kHz
93.75 - 187.5 -> 8 kHz
187.5 - 375.0 -> 4 kHz
375.0 - 750.0 -> 2 kHz
750.0 - 1500.0 -> 1 Khz
more than 1500.0 -> 500 Hz

Doesn't break forward/backward avrdude/usbasp compability (at least I
hope so ;)) - firmware just falls back to jumper setting.

Hope this will be useful

Jurgis


On Wed, Jan 9, 2008 at 6:56 PM, Thomas Fischl <address@hidden> wrote:
>
> Joerg Wunsch wrote:
>
> > You can never get too slow. :-) You could have a device being clocked
> > from a 32 kHz crystal oscillator, and with a CKDIV8 fuse programmed,
> > so the resulting CPU clock frequency were 4096 Hz.  In that case, the
> > ISP clock must be below 1024 Hz... (and be it only in order to
> > unprogram the mistakenly programmed CKDIV8 fuse again :).
>
> Okay. Then we should leave the software SPI function in the USBasp
> firmware and make the clock delays in it variable. This function can be
> used for frequencies lower than 187.5kHz and the hardware SPI for faster
> clocking.
>
> Thomas

avrdude.diff
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usbasp.diff
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