[avrdude-dev] Re: Implementation of of FTD2XX-based AVR programmer in avrdude

[Uwe Bonnes]

Johnathan Corgan <address@hidden> wrote:
> I've spent the day hacking together an experimental implementation of 
> serial programming via the FTDI FT232BM USB-to-serial converter bit bang 
> mode.  Mostly a success, so far.

> After familiarizing myself with the programmer_t abstraction and seeing 
> how it is implemented in par.c and other files, I was able to create a 
> new programmer type ('ftbb') and make a new programmer entry in 
> avrdude.conf that uses it.  I did consider first trying to fit into 
> Michael Holtz' bit bang structure but there were more differences than 
> similarities, so I went the new interface route.

> At the lowest level, there is a routine called ftbb_txrx() which sends 
> and receives 8 bits over the bit bang bus of the FTD2XX.

> pgm->cmd builds on this and sends four bytes of a command and records 
> the four bytes of the response.

> The other routines for open, close, enable, disable, initialize, erase, 
> etc., are straightforward, making the right calls to the FTDI DLL.

> I am able to use the terminal mode successfully with an ATMega8 for 
> everything I've tried so far.  All the memory space read commands from 
> the command line are working too.

> There does seem to be a subtle timing bug as I can do a chip erase from 
> the terminal but not from the command line--the SPI bus falls out of 
> sync and doesn't respond any further.  I do have the usleep() call with 
> the erase delay value in there, but maybe that's not where the problem lies.

> However--this implementation is *extremely slow*.  It accomplishes about 
>   four commands per second, so reading 16 bytes of eeprom takes, for 
> example, 4 seconds.  This is due ultimately to requiring a USB packet 
> per SCLK transition, with a 200ms or so fixed timeout inside the FTD2XX 
> device driver DLL.  (I know, Joerg warned about this--but stay with me.)

Learn about the latency timer inside the FT2232. I will encrease speed
substancial. Also try to send big chunks to the FT2232. This will encrease
speed too.


Bye

-- 
Uwe Bonnes                address@hidden

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
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