Re: [OpenOCD-user] FT2232 device

[Trampas S. <tr...@gm...>]

I did use a tri-state driver to pull the SWDIO low.

I also added a 10k pull up on the TMS/SWDIO as that even with tri-state the
SWDIO on the hardware I was using was too week.



On Tue, Aug 2, 2016 at 3:32 PM, Tomas Vanek <to...@us...>
wrote:

> On 02.08.2016 19:13, Trampas Stern wrote:
>
>> The resistor hack is basically a hack, but would be better if a Schottky
>> diode was used with a pull up resistor. This would simulate the TDI being
>> an open collector driver and only pulling down the SWDIO.  Also for some
>> hardware the debugger should have a pull up on the SWDIO.
>>
> Certainly not. Pull up on SWDIO is really weak, just to prevent line
> floating. Asymmetric drive of open collector with the capacity of a cable
> would have much steeper failing slope than rising - this would limit
> reachable frequency.
>
> If you don't want to use a hack, you should connect a 3-state driver from
> TDI output to SWDIO and configure a FT2232 pin as a signal to enable it.
> See kt-link.cfg.
>
> Tomas
>
>