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Re: [avr-gcc-list] AVR-GCC-list Digest, Vol 97, Issue 1

From: Joerg Wunsch
Subject: Re: [avr-gcc-list] AVR-GCC-list Digest, Vol 97, Issue 1
Date: Fri, 8 Feb 2013 21:07:58 +0100 (MET)

Gerrit Bosch <address@hidden> wrote:

> A logic analyser showed that the signals from the m2560 and the
> tiny85 were different. The tiny85 produced something like spikes.

Is the ATtiny85 located in an STK600 socket board, or off-board?

If the latter, perhaps your ISP lines are too long, or perhaps you
forgot to add bypass capacitors to the Vcc line?

> Not being an expert I read at the AVRDUDE man-page about the -B
> parameter. A value of 0.1e-120 solved the problem.

Really 0.1E-120?  That would be strange. :)

For a standard 1-MHz-clocked AVR, -B10 normally ought to be a fairly
conservative setting.  For historical reasons, the ISP clock is given
as the period time in microseconds, so -B10 corresponds to 100 kHz.
The requirement is to be below 1/4 of the CPU clock, so for a default
CPU clock of 1 MHz, your ISP frequency must be below 250 kHz
(including all possible tolerances).  -B4 might be at risk, but -B5 is
guaranteed to satisfy this condition.  -B10 has shown to improve the
tolerance against all kind of poor cabling etc., at the cost of some
programming speed of course.

cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

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