So.... which JTAG connector should I use? - Page 1
Forum section: electronics / general

author: tom66
author_rank: Super Contributor
timestamp: May 04, 2013, 05:32:31 pm
content: Seems that JTAG is used to program most ARM microcontrollers these days. I have just started design of a board using one, and I need to choose a programmer to use. There's a vast selection, but I'd prefer to put a connector on my board that was considered fairly standard -- maybe one of the bigger manufacturers uses it on their dev boards, for example. I'm using an STM32F4 processor -- but I think this would apply to most micros. Any ideas?I have a LuminaryMicro LM3S1968 eval board which has a JTAG-SWD connector. I think this makes it capable of JTAG programming devices, but probably only TI devices. Anyone know if it will work with STM's devices?

author: rsjsouza
author_rank: Super Contributor
timestamp: May 08, 2013, 01:41:15 pm
content: The most basic and "standard" ARM JTAG connector is the large 20-pin one - you can't go wrong with this (your LM3S1968 boardhas one on top of the LCD)ARM is also trying to push a higher density 10-pin connector (present in some Stellaris boards such asthis one) but I don't think is ubiquitous as the other one.Good information about these connectors ishere. There is also a good ARM documenthere.

author: benemorius
author_rank: Regular Contributor
timestamp: May 08, 2013, 03:54:51 pm
content: I know how you feel looking for a standard to go with, but I don't think you'll find anything terribly satisfying in this case. There isn't an overwhelmingly standard choice aside from the huge .1" 20 pin. The 10 pin mentioned above is probably the next best thing.

author: tom66
author_rank: Super Contributor
timestamp: May 08, 2013, 06:19:20 pm
content: Great. Next question... do I need to buy an ST-Link to program my STM32, or can any JTAG programmer work (is there a universal interface over USB for these things that any programmer will use?)

author: rsjsouza
author_rank: Super Contributor
timestamp: May 08, 2013, 06:44:53 pm
content: You will need to find a compatible JTAG emulator across the various devices you intend to use. One that has great compatibility across several manufacturers isSegger's Jlink- they claim to support any Cortex M cores, which is ok for single-core devices like the ones you mentioned (if you move to a multi-core device, things will be different due to JTAG routing inside the device).Even Code Composer Studio has support for it. Checkhere.

author: andyturk
author_rank: Frequent Contributor
timestamp: May 08, 2013, 06:45:41 pm
content: Quote from: tom66 on May 08, 2013, 06:19:20 pmIf you're going with STM34F4, why not use SWD instead of JTAG? The Discovery boards have a built-in SWD interface that you can use to program/debug an external mcu via a 6-line cable.A STM32VLDiscovery board is controlling a STM32F4Discovery here:The ST-LINK usb dongle is handy too, and required if your board doesn't run at 3V. The project below runs at 1.8V, so I had to use the ST-LINK:

author: tom66
author_rank: Super Contributor
timestamp: May 08, 2013, 07:00:40 pm
content: Interesting idea. I could break out both. I've got enough space on the board. And the STM discovery boards are -much- cheaper than a dedicated ST-LINK programmer. (I can get one for £6.65:http://uk.farnell.com/stmicroelectronics/stm32f0discovery/eval-kit-stm32f0-with-st-link-v2/dp/2096251)My board runs at 3.3V so no problem there.