[15155]

JTAG is hard to do. RP PIO (USB FS), TI PRU (bad toolchains), or NXP FlexIO are really required to do it correctly (or you can do it "okay" with a capable SPI controller.)

[gaudat]

FT2232H with libMPSSE. It is even advertised as a USB-to-JTAG chip.

[15155]

Terrible drivers, pinouts, etc. for the ridiculous price of $6-10.

[hkwerf]

Could you explain why? A JTAG master seems easily bit-bangable unless you require high data rates?

[bogantech]

Indeed my understanding is that it should not require crazy hardware requirements - it's a serial protocol clocked by the programmer.

Here's an Arduino project to program CPLDS/FPGAs using XSVF files https://github.com/wschutzer/xsvfduino

I'd say that the cheap programming cables are abundant and already compatible with the vendor tools so there's not much motivation to reinvent the wheel.

[15155]

TMS is hard to manage. High data rates are exactly the issue.

Any MCU can bitbang JTAG at 100kHz. Try doing it at 30 MHz sustained.

[bvan]

Whatever happened to the Jtagulator? It no longer seems to be available.