JTAG with (not of) Teensy

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I have an old Olimex parallel-port Wiggler clone JTAG, but no easy-to-use parallel port any more. So I need a new JTAG dongle.

Looking at the OpenOCD docs, they have a bit-bang driver that (apparently) is intended to control a simple JTAG device using about a dozen single-character commands. It seems like that would be really easy to implement on a Teensy, so the Teensy would control the 5 JTAG lines and report the state of TDO back to OpenOCD.

My question is, has anybody implemented this yet?

I just built a recent version of OpenOCD, and I'm trying to get oriented by getting it to talk to an FTDI-2232 JTAG that's embedded into a Stellaris Evalbot. (Unfortunately, it's not a stand-alone FTDI JTAG dongle; the chip is hardwired to the rest of the Evalbot.) It's going slowly, but I expect I'll be able to get OpenOCD running without too much more trouble. Then on to figuring out how the bitbang interface is supposed to work...
True, there's several options (including cheap ones) but I have some Teensies! Anyway, it turns out that there's an OpenOCD driver for the BusPirate, which I suspect will happily talk to appropriate firmware on a Teensy, too. (I wouldn't be surprised if it's very similar to the BusBlaster driver, but haven't checked.) I think I'll be able to write a quick Teensy program that enumerates as a serial port (PJRC already provides that code) and then just interacts with OpenOCD using the bit-banging interface. Will send up my implementation if I can get it working.

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