Re: [avrdude-dev] Yet another config parameter

[Joerg Wunsch]

As Brian Dean wrote:

> > ..., using the port-supplied power is the
> > only way to make that m163 enter programming mode at the first try,
> > while with external power, it only enters programming mode after ~ 30
> > attempts.

> I wonder if this is a result from being able to better control the
> state of /RESET and SCK when power is applied when the power is
> coming from the parallel port, than externally.  The datasheet says
> that /RESET and SCK must be held low at the time VCC is supplied
> with power when preparing to enter programming mode.

Ah yes, now i see how this might happen.  Surprise that this doesn't
happen with any other AVR though.  In particular the m128 board is
also externally powered.

> It goes on to say that if
> you can't guarantee this, you need to give /RESET a positive pulse
> while holding SCK low.

...except for the AT90S1200 that doesn't offer this option.  This was
probably the first AVR that offered ISP mode.

I wonder whether we should provide a "hold /RESET low until someone
presses <Enter>" mode for avrdude, so a user can:

. start avrdude, telling it to assert /RESET,
. connect the AVR's power supply,
. tell avrdude that it could start now (by pressing Enter).

Otherwise, in particular programming an AT90S1200 where the circuit
cannot be powered from the parallel port might become impossible.  (In
my very old '1200 test board, i can always use the programmer's power
supply, thus i didn't notice any problem.)

-- 
J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/