Re: [OpenOCD-user] FT230X interface

[Angus G. <gu...@pr...>]

On Thu, Apr 30, 2015 at 08:33:47AM +0300, Paul Fertser wrote:
> On Wed, Apr 29, 2015 at 10:15:47PM -0700, Myles Watson wrote:
> > I was looking through the info manual, but couldn't find information
> > on how to use ftdi_layout and friends to tell openocd which CBUS
> > pins to use.
> 
> Basically, MPSSE JTAG mode leaves you no choice about TDO, TDI, TCK,
> TMS. Hence no configuration for that. To understand how JTAG pins are
> used to talk SWD please see swd-resistor-hack.cfg.

Hi Myles & Paul,

I'm not an FTDI expert, but I think the difference may be that FT230X
has no MPSSE engine. It has some CBUS GPIO pins, but you have to use
the different "bit bang" USB protocol to drive them.

FTDI bit banging might be suitable for JTAG or SWD, but AFAIK it's a
lot slower as it doesn't do the pipelining that MPSSE does. It's also
not supported in openocd, to my knowledge. :(

The comments in the headers of src/jtag/drivers/ftdi.c and
src/jtag/drivers/mpsse.h may also be helpful.

Cheers,


Angus