Comments on: JTAGulator https://www.epanorama.net/blog/2013/08/14/jtagulator/ All about electronics and circuit design Tue, 14 Apr 2026 22:35:42 +0000 hourly 1 http://wordpress.org/?v=3.9.14 By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-1832424 Tue, 16 Jul 2024 20:23:36 +0000 http://www.epanorama.net/blog/?p=21037#comment-1832424 https://blog.samtec.com/post/what-is-a-jtag-connector/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-1827409 Mon, 13 May 2024 11:48:52 +0000 http://www.epanorama.net/blog/?p=21037#comment-1827409 https://hackaday.com/2024/05/12/jtag-hacking-an-ssd-with-a-pi-a-primer/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-1810375 Sat, 12 Aug 2023 11:32:09 +0000 http://www.epanorama.net/blog/?p=21037#comment-1810375 https://hackaday.com/2023/08/11/using-jtag-to-dump-the-xboxs-secret-boot-rom/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-1682853 Sun, 21 Jun 2020 11:23:41 +0000 http://www.epanorama.net/blog/?p=21037#comment-1682853 A Hacker’s Guide To JTAG
https://hackaday.com/2020/04/08/a-hackers-guide-to-jtag/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-1234206 Sat, 20 Sep 2014 06:29:17 +0000 http://www.epanorama.net/blog/?p=21037#comment-1234206 Given an Arduino compatible microcontroller JTAGenum scans pins[] for basic JTAG functionality and can be used to enumerate the IR for undocumented opcodes.

https://github.com/cyphunk/JTAGenum/

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-34315 Thu, 03 Oct 2013 06:37:10 +0000 http://www.epanorama.net/blog/?p=21037#comment-34315 JTAGulator
http://www.grandideastudio.com/portfolio/jtagulator/

JTAGulator is an open source hardware tool that assists in identifying OCD connections from test points, vias, or component pads on a target device.

Assembled JTAGulators are available from Parallax, Inc.

JTAGulator $159.99
http://parallax.com/product/32115

]]> By: Tomi Engdahl https://www.epanorama.net/blog/2013/08/14/jtagulator/comment-page-1/#comment-34314 Thu, 03 Oct 2013 06:25:48 +0000 http://www.epanorama.net/blog/?p=21037#comment-34314 JTAGulator Finds Debug Interfaces
http://hackaday.com/2013/10/02/jtagulator-finds-debug-interfaces/

[Joe Grand] has come up with a tool which we think will be useful to anyone trying to hack a physical device: The JTAGulator. We touched on the JTAGulator briefly during our DEF CON coverage, but it really deserves a more in-depth feature. The JTAGulator is a way to discover On Chip Debug (OCD) interfaces on unfamiliar hardware.

Open any cell phone, router, or just about any moderately complex device today, and you’ll find test points. Quite often at least a few of these test points are the common JTAG / IEEE 1149.1 interface.

JTAG interfaces have 5 basic pins: TDI (Test Data In), TDO (Test Data Out), TCK (Test Clock), and TMS (Test Mode Select), /TRST (Test Reset) (optional).

If you’re looking at a PCB with many test points, which ones are the JTAG pins? Also which test points are which signals?

The idea is simple: Connect the JTAGulator to the test points on the PCB under test, issue a few commands via a serial terminal, and let the JTAGulator do the rest. It performs a brute force approach on every permutation of pins, issuing basic JTAG commands – either IDCODE or BYPASS, and looking for a response. If any valid responses are received, the JTAGulator displays the found interface’s pinout.

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