Ideas on what type of JTAG device to purchase - Page 1
Forum section: electronics / general

author: stuartbh
author_rank: Newbie
timestamp: March 28, 2023, 10:04:22 am
content: Forum members,Whilst this may be a common question, I am going to try to best articulate my intended use case in the initiate and then I pray everyone here will feel fully armed (excuse the pun) to provision their opinion and counter questions in pursuance of making a reasonable choice as to a JTAG device.I am an OpenWRT user and have bricked a router or two from time to time. Most of the time they have serial interfaces I can use to recover them, though some have JTAG also. It is my main use case for JTAG (to de-brick routers) and I would likely use OpenOCD as my software (I am fully Linux conversant as I have been a Linux consultant for several decades). I also have an entirely unsupported router that I wish to try to get OpenWRT to work on and I may also need JTAG though I suspect it has a serial port too. Lastly, I wish to get into more hardware hacking and having a faster and more capable JTAG device rather than just wanting to buy the dirt cheapest thing would be something I'd be very open too. It is something I suspect I'll buy and not need to repurchase for a while so getting a better one for a few dollars more is okay with me if it makes sense.I realize that this question has been asked before, but the hardware that is available changes as time goes on as does do the capabilities, so I do apologize if it seems an asked and answered question.Thanks in advance to all respondents for their time and consideration regarding the instant matter.Stuart

author: CaptDon
author_rank: Super Contributor
timestamp: March 28, 2023, 02:00:52 pm
content: Have you tried posting this question in the FPGA forum?

author: stuartbh
author_rank: Newbie
timestamp: March 28, 2023, 02:07:34 pm
content: Quote from: CaptDon on March 28, 2023, 02:00:52 pmNo, I surely did not, though I fashioned myself a beginner and saw this forum and posted away. Make no mistake, I am fully desirous of availing myself of the most knowledgeable forum members that might be able to assist me and so using the right forum is surely of interest to me.Is it possible for a moderator to move this posting to the FPGA forum or do you recommend I re-post the message in the FPGA forum?Stuart

author: BillyO
author_rank: Super Contributor
timestamp: March 28, 2023, 02:10:49 pm
content: Cross posting is frowned on. Maybe a mod can move it.But to try to answer the question, I'd go with something that will work with the software. One of the first USB JTAG devices was the Altera USB-Blaster. It's old and was popular at one time but was also supported by most software. Maybe one of those or something that claims to be compatible.

author: TheDreadPirateRon
author_rank: Newbie
timestamp: April 09, 2023, 09:30:59 pm
content: According to the OpenOCD documentaion, it does indeed support the USB Blaster. In addition, it supports USBProg, an opensource desgin with a debian package for the drivers.I found a repo of somebody's schematics here [https://github.com/AndreyDobrovolskyOdessa/usbprog][/https://github.com/AndreyDobrovolskyOdessa/usbprog]

author: darkspr1te
author_rank: Frequent Contributor
timestamp: April 10, 2023, 09:42:11 am
content: Quote from: stuartbh on March 28, 2023, 10:04:22 amI recently answered this question herehttps://www.eevblog.com/forum/chat/segger-programmer-prices/msg4799327/#msg4799327but what I covered there was more "just jtag" rather than "more h/w hacking" , As someone who does hacking of s/w & h/w for fun i have built up various tools but my always goto device is the Dangerous Protypes Bus Pirate, it supports many protocols (i2c,spi,uart,jtag,swd, bit bash) , is open source too. supporting 1.8v(external psu required) , 3.3, 5v direct on the board.second to my bus pirate is my two jtag devices, one is a black magic probe running on $5 blackpill and the other Dangerous protypes bus Blaster, this is a ftdi+cpld that allows you to configure a front end, there are a few out there and quite a few support advance jtag hacking. example is using kt-link front end you can run swd hacks like stm DFU dump as well as the SWD over run hack or if you need to run some factory software and need segger jlink support then all you do is reflash the cpld. this is also true if you need support in apps like urjtag which can access a lot of broadcom routers where openocd cannot, so effectively one device can emulate a few devices in your toolbox.Also all the above are open source and this is very handy,darkspr1te