Free and Open On-Chip Debugging, In-System Programming
and Boundary-Scan Testing
Copyright (c) 2004, 2005, 2006 Dominic Rath
The debugger uses an IEEE 1149-1 compliant JTAG TAP bus master to access on-chip
debug functionality available on ARM7 and ARM9 based microcontrollers /
User interaction is realized through a telnet command line interface and a gdb
(The GNU Debugger) remote protocol server.
1. JTAG hardware
Currently, OpenOCD supports three types of JTAG interfaces:
- Parallel port wigglers. These devices connect to a PC's parallel port,
providing direct access to the JTAG lines. The OpenOCD contains descriptions
of a few Wiggler layouts, including the original 'Wiggler' design. Other
layouts (i.e. mapping of parallel port pins to JTAG lines) can be added easily.
Typical Wiggler speeds are around 12kByte/s code download to an ARM7's RAM.
- The Amontec JTAG Accelerator. This is a configuration for Amontec's Chameleon
dongle, a parallel port interface based on a Xilinx CoolRunner CPLD. It uses
the IEEE1284 EPP parallel port specification, providing many times the
performance achievable with wiggler-style devices. Additional information is
available on www.amontec.com.
Typical JTAG Accelerator speeds are around 120-160kByte/s to an ARM7's RAM.
- FTDI FT2232 based USB devices. The FT2232 (but not FT232 or FT245) features a
multi-protocol synchronous serial engine (MPSSE) that can be used to run the
serial JTAG protocol. There are several implemenations of FT2232 based devices:
* USBJTAG: http://www.fh-augsburg.de/~hhoegl/proj/usbjtag/usbjtag.html
The USBJTAG was designed by Prof. Hubert Hoegl to provide a high-speed USB
interface for use with the OpenOCD. Schematics are available at the USBJTAG
website, and a homebrew device can easily be built using the FTDI evaluation
* Amontec JTAGkey: www.amontec.com
The Amontec JTAGkey offers support for a wide variety of target voltages from
1.4V to 5V. It also allows the JTAG lines and reset signals to be tri-stated,
allowing easy interfacing with a wide variety of targets.
* Olimex ARM-USB-OCD: www.olimex.com
The Olimex ARM-USB-OCD offers support for a wide vriety of target voltages from
2.0V to 5V. It also allows targets to be powered from the ARM-USB-OCD and
features and additional RS232 UART.
* eVerve Signalyzer: www.signalyzer.com
The Signalyzer offers support for a wide variety of target voltages from 1.2V to
5.5V. A second connector provides access to a TTL level UART.
All FT2232 based devices may be accessed using either FTDI's proprietary FTD2XX
library (www.ftdichip.com) or using an open-source replacement from
http://www.intra2net.com/de/produkte/opensource/ftdi/index.php, also included
with many Linux distributions.
2. Supported cores
This version of openocd supports the following cores:
Support for Intel XScale CPUs (PXA25x, PXA27x and IXP4xx) is currently being
The OpenOCD is only tested with little-endian targets, but support for
big-endian is planned. If you're interested in helping with this (and you
happen to have a big-endian ARM7/ARM9 system, feel free to contact
Dominic.Rath <at> gmx.de.
3. Host platforms
OpenOCD was originally developed on x86-Linux, but has since then been ported
to run on Windows/Cygwin, native Windows with MinGW, FreeBSD, x86-64-Linux and
(though it's not fully working yet) PowerPC OS-X.
Documentation for the OpenOCD is hosted in the Berlios OpenFacts Wiki at
OpenOCD is licensed under the terms of the GNU General Public License, see the
file COPYING for details.