libftdi Archives

Subject: Re: [libftdi 0.18] SPI with CBUS Bit-banging FT232H

From: Alex Stefan <alexandru.stefan@xxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Mon, 04 Jul 2011 16:57:15 +0300
On Tue, 2011-06-28 at 15:06 +0200, Uwe Bonnes wrote:
> >>>>> "Alex" == Alex Stefan <alexandru.stefan@xxxxxxxxxxx> writes:
> 
>     Alex> Hello, I am working on implementing a SPI protocol using
>     Alex> bit-banging on the CBUS interface of a FT232H chip. The purpose
>     Alex> would be to program another chip's flash memory via USB.
> 
>     Alex> The one I can't figure out is how to correctly time the SPI
>     Alex> operations.  I mean, how can I output a precise clk signal on SCK
>     Alex> using bit-banging.
> 
> Why do you want do bitbang with the FT232H?  MPSSE mode is much easier to
> use.
> 
> Bye 

I need to use CBUS bitbang because the MPSSE pins will be used for UART
communication afterwards. 

Anyway, I have implemented everything, works correctly, but not fast
enough. My SPI tx/rx function runs at an approximate rate of 300 BPS
which translates into a huge amount of time to flash a 30 KB image to
the chip. 

Has anyone encountered this problem so far? From what I can tell, the
problem is with the USB driver functions in the kernel, but I can't
figure out how to solve it. Any ideas?

Thanks,
Alex


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