On Wed, Dec 19, 2012 at 5:22 PM, Ing. Rodrigo Alejandro Melo <
[email protected]> wrote:
>
> The first options are easy to understand, because are similar to
> previous driver, but I would like to know what mean the last 3? Is
> somewhere explained?
>
I've mentioned it in the commit comment, several time on the mailing list
and in gerrit comments but never gotten around to updating the docs.
I'll describe it once again and try to convert the answer into a patch for
the manual.
>
> >>>
> interface ftdi
> ftdi_device_desc "Dual RS232-HS"
> ftdi_vid_pid 0x0403 0x6010
> ftdi_channel 1
>
> ftdi_layout_init 0x0c08 0x0f1b
>
These are the initial values for the FTDI GPIO data and direction
registers, respectively.
ftdi_layout_signal nTRST -data 0x0100 -noe 0x0400
> ftdi_layout_signal nSRST -data 0x0200 -noe 0x0800
>
The values are FTDI GPIO register bitmasks to tell the driver the
connection and type of the output buffer driving the respective signal. The
value after -data is the bitmask for the pin(s) connected to the data input
of the output buffer. There is also an -ndata option that's used with
inverting data inputs. The -oe (or -noe) option tells where the
output-enable (or not-output-enable) input to the output buffer is
connected.
Both -(n)data and -(n)oe need not be specified. For example, a simple
open-collector transistor driver would be specified with -oe only. In that
case the signal can only be set to '0' (drive low) or 'z' (Hi-Z) and the
driver will complain if the signal is set to '1' (drive high). Which means
that if it's a reset signal, reset_config must be specified as open_drain,
not push_pull.
A special case is provided when -data and -oe is set to the same bitmask.
Then the FTDI output is considered being connected straight to the target
without any buffer. The FTDI pin is then switched between output and input
as necessary to provide the full set of '0', '1' and 'z' signal states. I
all other cases, the pins specified in a signal definition are always
driven by the FTDI.
/Andreas
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