Openocd

Quick Reference

There is an even older Quick Reference for revision 211, (Nov 14 2007): oocd-quickref-211.pdf (4 pages) and oocd-quickref-compact-211.pdf (2 pages).

Also the GDB Quick Reference (Version 5) might be of interest because OpenOCD needs the GNU Debugger as front-end.

JTAG Interfaces

OpenOCD can talk to nearly any hardware which is able to drive the JTAG signals. Currently the sourcecode supports the following interfaces:

Parallel Port Interfaces

• Wiggler

  The Wiggler is a cheap parallel port JTAG interface originally developed by Macraigor. On a write or read access to/from the parallel port a single bit is sent to TCK, TMS, TDI and a bit is read from TDO. Write/read accesses at the parallel port (in legacy mode) can be at a maximum rate of 200.000 to 400.000 per second. This is the reason why the Wiggler is a rather slow JTAG interface. Meanwhile the schematic is free. Be aware that different versions of the schematic exist. Following is the schematic from Dominic Rath's OpenOCD thesis:

  

  Here is another schematic found at the homepage of the H-JTAG project: WIGGLER.pdf (added on 2006-12-13)

• JTAG Accelerator

  The JTAG Accelerator is a more clever implementation of a JTAG interface using shift registers. It does also support the RTCK feature for adaptive clocking ("return clock"). The programming interface to the Accelerator is open and well described. The Accelerator is implemented in the "Chameleon" parallel port adaptor by Amontec (www.amontec.com).

  The Chameleon dongle contains a reconfigurable CPLD. The idea behind this dongle is to buy one adaptor and to change its identity by reconfiguring the CPLD. Amontec's homepage offers many different configurations from CPLD/FPGA download cables to BDM and JTAG interfaces. Besides the Accelerator configuration there is also a free configuration for the Wiggler.

USB

• The USB to JTAG interfaces based on the FT2232 chip are described on this page: http://www.fh-augsburg.de/~hhoegl/proj/usbjtag/usbjtag.html

• USBprog - since 2007 there is another USB-to-JTAG interface which does not use an FT2232. Instead, it is based on a National Semiconductor USB bridge USBN9604 and an Atmel AVR Mega32 microcontroller. Beside its use as a JTAG adaptor for OpenOCD it can also be used for other purposes by reprogramming the AVR flash memory from a pool of ready to use firmwares. For example the device can also act as a AVRISP mkII or as an AVR JTAG debugger (JTAGICE mkI) or as a programmer for 8051 controllers. USBprog is a project of Benedikt Sauter, one of my diploma students. It was presented at Embedded World 2007 trade fair in Nuremberg (here are some fotos). Please go to http://www.embedded-projects.net to read more about this nice adaptor.
  
  A foto of USBprog, revision 3.

Photographs

• I shot these photographs at Dominic Rath's diploma thesis talk in autumn 2005.

  Dominic starting to talk about his thesis.	Cogent CSB337 (with Atmel AT91RM9200) controlled by Openocd and a USB-to-JTAG interface.	A board based on an ARM720T connected to the Chameleon POD "Wiggler".
  Dominic Rath mit Arkadius Nowakowski

• Embedded World 2006 (14-16 Feb), Nürnberg
  Find all photographs here: http://www.fh-augsburg.de/~hhoegl/tmp/eworld/embedded-world-2006/fotos/