doc: Add documentation for the ftdi driver
Change-Id: I1ade2eb187b404141051d9f59ba06e8e6e5d51aa Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com> Reviewed-on: http://openocd.zylin.com/1099 Tested-by: jenkins Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
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Andreas Fritiofson
Spencer Oliver
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117
doc/openocd.texi
117
doc/openocd.texi
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@ -2462,6 +2462,10 @@ Cirrus Logic EP93xx based single-board computer bit-banging (in development)
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@deffn {Interface Driver} {ft2232}
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FTDI FT2232 (USB) based devices over one of the userspace libraries.
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Note that this driver has several flaws and the @command{ftdi} driver is
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recommended as its replacement.
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These interfaces have several commands, used to configure the driver
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before initializing the JTAG scan chain:
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@ -2545,6 +2549,119 @@ ft2232_vid_pid 0x0403 0xbdc8
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@end example
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@end deffn
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@deffn {Interface Driver} {ftdi}
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This driver is for adapters using the MPSSE (Multi-Protocol Synchronous Serial
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Engine) mode built into many FTDI chips, such as the FT2232, FT4232 and FT232H.
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It is a complete rewrite to address a large number of problems with the ft2232
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interface driver.
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The driver is using libusb-1.0 in asynchronous mode to talk to the FTDI device,
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bypassing intermediate libraries like libftdi of D2XX. Performance-wise it is
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consistently faster than the ft2232 driver, sometimes several times faster.
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A major improvement of this driver is that support for new FTDI based adapters
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can be added competely through configuration files, without the need to patch
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and rebuild OpenOCD.
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The driver uses a signal abstraction to enable Tcl configuration files to
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define outputs for one or several FTDI GPIO. These outputs can then be
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controlled using the @command{ftdi_set_signal} command. Special signal names
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are reserved for nTRST, nSRST and LED (for blink) so that they, if defined,
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will be used for their customary purpose.
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Depending on the type of buffer attached to the FTDI GPIO, the outputs have to
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be controlled differently. In order to support tristateable signals such as
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nSRST, both a data GPIO and an output-enable GPIO can be specified for each
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signal. The following output buffer configurations are supported:
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@itemize @minus
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@item Push-pull with one FTDI output as (non-)inverted data line
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@item Open drain with one FTDI output as (non-)inverted output-enable
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@item Tristate with one FTDI output as (non-)inverted data line and another
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FTDI output as (non-)inverted output-enable
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@item Unbuffered, using the FTDI GPIO as a tristate output directly by
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switching data and direction as necessary
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@end itemize
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These interfaces have several commands, used to configure the driver
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before initializing the JTAG scan chain:
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@deffn {Config Command} {ftdi_vid_pid} [vid pid]+
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The vendor ID and product ID of the adapter. If not specified, the FTDI
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default values are used.
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Currently, up to eight [@var{vid}, @var{pid}] pairs may be given, e.g.
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@example
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ftdi_vid_pid 0x0403 0xcff8 0x15ba 0x0003
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@end example
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@end deffn
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@deffn {Config Command} {ftdi_device_desc} description
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Provides the USB device description (the @emph{iProduct string})
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of the adapter. If not specified, the device description is ignored
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during device selection.
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@end deffn
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@deffn {Config Command} {ftdi_serial} serial-number
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Specifies the @var{serial-number} of the adapter to use,
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in case the vendor provides unique IDs and more than one adapter
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is connected to the host.
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If not specified, serial numbers are not considered.
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(Note that USB serial numbers can be arbitrary Unicode strings,
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and are not restricted to containing only decimal digits.)
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@end deffn
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@deffn {Config Command} {ftdi_channel} channel
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Selects the channel of the FTDI device to use for MPSSE operations. Most
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adapters use the default, channel 0, but there are exceptions.
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@end deffn
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@deffn {Config Command} {ftdi_layout_init} data direction
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Specifies the initial values of the FTDI GPIO data and direction registers.
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Each value is a 16-bit number corresponding to the concatenation of the high
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and low FTDI GPIO registers. The values should be selected based on the
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schematics of the adapter, such that all signals are set to safe levels with
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minimal impact on the target system. Avoid floating inputs, conflicting outputs
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and initially asserted reset signals.
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@end deffn
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@deffn {Config Command} {ftdi_layout_signal} name [@option{-data}|@option{-ndata} data_mask] [@option{-oe}|@option{-noe} oe_mask]
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Creates a signal with the specified @var{name}, controlled by one or more FTDI
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GPIO pins via a range of possible buffer connections. The masks are FTDI GPIO
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register bitmasks to tell the driver the connection and type of the output
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buffer driving the respective signal. @var{data_mask} is the bitmask for the
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pin(s) connected to the data input of the output buffer. @option{-ndata} is
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used with inverting data inputs and @option{-data} with non-inverting inputs.
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The @option{-oe} (or @option{-noe}) option tells where the output-enable (or
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not-output-enable) input to the output buffer is connected.
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Both @var{data_mask} and @var{oe_mask} need not be specified. For example, a
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simple open-collector transistor driver would be specified with @option{-oe}
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only. In that case the signal can only be set to drive low or to Hi-Z and the
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driver will complain if the signal is set to drive high. Which means that if
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it's a reset signal, @command{reset_config} must be specified as
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@option{srst_open_drain}, not @option{srst_push_pull}.
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A special case is provided when @option{-data} and @option{-oe} is set to the
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same bitmask. Then the FTDI pin is considered being connected straight to the
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target without any buffer. The FTDI pin is then switched between output and
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input as necessary to provide the full set of low, high and Hi-Z
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characteristics. In all other cases, the pins specified in a signal definition
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are always driven by the FTDI.
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@end deffn
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@deffn {Command} {ftdi_set_signal} name @option{0}|@option{1}|@option{z}
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Set a previously defined signal to the specified level.
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@itemize @minus
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@item @option{0}, drive low
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@item @option{1}, drive high
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@item @option{z}, set to high-impedance
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@end itemize
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@end deffn
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For example adapter definitions, see the configuration files shipped in the
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@file{interface/ftdi} directory.
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@end deffn
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@deffn {Interface Driver} {remote_bitbang}
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Drive JTAG from a remote process. This sets up a UNIX or TCP socket connection
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with a remote process and sends ASCII encoded bitbang requests to that process
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