JTAG Wiggler - Simple Buffered JTAG Cable
Looking for JTAG Cable? Read about JTAG wigglers, and programmers. The JTAG Wiggler cable is used for either JTAG or BDM debugging. It connects to the standard parallel port of the PC. This is a stable and easy to use device.
The JTAG Wiggler cable is a low-cost interface used for programming of microcontroller based embedded systems. Wiggler connects to the standard parallel port of a host PC. The other side connects to an OCD (On-Chip Debug) port of the target system. This port may be JTAG, E-JTAG, OnCE, COP, BDM, or any of several other types of connections.
The Wiggler is the cheapest of Macraigor’s line of OCD connection devices. It provides all the same functionality as more expensive products.The Wiggler supports configurable JTAG clock rates between about 60 KHz and 380 KHz. The Wiggler will perform best with those ports that are configured as EPP (enhanced parallel port) compatible but will also work with most other parallel port modes. The Wiggler is compatible with Windows hosts. Macgraigor offers a free software called OCDRemote which works with any wiggler compatible JTAG Cable. There is also other software which works with the Wiggler. One of the most popular utilities comes from a project called jtag-tools by openwince. Jtag-tools runs on both Windows (compiled with cygwin) and Linux.
The Wiggler is a very simple device that primarily acts as a signal buffer between parallel port signals and the target JTAG/BDM signals. Depending on the target processor, power may be supplied by an external 5V power supply or directly from the parallel port and/or partially from the target device itself.
This type of JTAG cable is a bit more complicated than the simple unbuffered one, therefore a list price of $150 USD. The advantage of a buffered cable is that it is not as constrained as to length and is more immune to noise and static, thus permitting a higher data transfer rate.
Although it is also fairly easy to construct a compatible JTAG cable you can check other JTAG cables that are compatible with the original JTAG Wiggler interface. Many suppliers offer cheap alternatives which are fully compatible with Macraigor OCD Commander. The wire between DATA6 (pin 8 on the LPT DB-25) and ERROR (pin 15) is used to identify a presence of the Wiggler cable and is required by some JTAG software. It may be omitted for Hairydairymaid debrick utility. Buffered JTAG Wiggler cable requires a voltage source to operate. Usually +3.3 volts is needed. The buffer IC may take a Vcc from the PC LPT. It is possible to get a wiggler compatible JTAG cable for as low as $20. Check dealers and prices.
The original Wiggler is fully compatible with all of Macraigor’s software tools, including the free OCD Commander debugger, free GNU toolkit distributions, OCD Flash Programmer application, and the production line test tools. In addition, several commercial third-party debuggers work with the Wiggler. Most compatible interfaces can be used for programming ARM microcontrollers family.
There is also a USB compatible wiggler - the usbWigger. It is a USB interface for JTAG and BDM debugging. Faster than the classic parallel port Wiggler, it is a stable, easy to use device and is fully compatible with all of wiggler software. In addition, it is a true USB 2.0 high speed device.