[avrdude-dev] Re: avrdude-dev Digest, Vol 12, Issue 4

[Lou Cypher]

> There is neither a commandline- nor a config-option for setting the 
> SPI-speed. SPI is running at maximum speed, which is determined by 
> the time needed for an "out" or "in" instruction. That is more than 
> 1.6us for changing a port-bit, IIRC, which is usually slow enough.

Don't forget that common optocouplers do have a very slow propagation time, 
i.e. 4N25 and 4N35 are specified by Agilent to have a typical rise/fall time 
of 3 us, and someway similar are devices like Toshiba TLP521; in this case a 
1.6 us pulse gets completely lost.

A good choice could be with 6N135, 6N136 or even better 6N137, that are all 
fast enough, and quite common devices.

Lou