Re: [avrdude-dev] PDI capable bitbang programmers?

[Szymon Ulatowski]

On 05/05/2013 10:52 AM, "Ing. Daniel Rozsnyó" wrote:
> I have started to compare TPI and PDI - seems very similar. The TPI 
> has a dedicated reset wire, so PDI looks like a subset of TPI, with no 
> modification required.

last year i considered implementing PDI on FTDI but i gave up after 
learning that FT232R is unable to produce long and stable sequences of 
clock signal because of its hardware bug - the chip spits out all 
received data very quickly instead of buffering the packets and clocking 
output pins according to the configured frequency - see "TN_120 FT232R 
Errata Technical Note" - "3.1.2 BitBang Mode variable Pulse Width" 
http://www.ftdichip.com/Support/Documents/TechnicalNotes/TN_120_FT232R%20Errata%20Technical%20Note.pdf
and this is very unfortunate because PDI requires at least 10kHz clock - 
ideally we would configure the output clock to 20kHz (or more) and send 
an USB packets of 01010101 - but they screwed it and the result is a 
quick burst of clock followed by a pause (and pausing the clock 
disconnects PDI) :-P
so i gave up and decided to implement PDI in USBASP that is so 
ubiquitous and cheap
http://szulat.blogspot.com/2012/08/atxmega-programmer-for-050.html

but of course the FTDI implementation would be so much better (if it is 
really possible) and i wish luck to anyone trying to accomplish this goal!

sz.