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I have a Segger's Jlink EDU probe which I used for debugging and programming various ARM based MCU's. But now I have to work with this LPC4088 QS board which has a smaller pitch 20-pin JTAG connector that usual one. So I am searching for something like this:

enter image description here

to transform my large pitch JTAG cable to smaller pitch one. BUT The one on the picture (the smaller one) has only 10 pins while I need 20-pins. Does anyone know of any similar circuit like the one on the picture but with two 20-pin connectors (larger and smaller one)?

This is the schematics of the JTAG interface on my board. It looks like more than 10 pin's are needed:

enter image description here

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  • \$\begingroup\$ In reality, for an SWD target you need only a ground, SWDIO, SWCLK and maybe a reset and an I/O reference voltage (depending on the target and what the design of the tap adapter assumes). \$\endgroup\$ Nov 28, 2015 at 2:27

4 Answers 4

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Maybe this one would work for you:

enter image description here

Here is another possibility of a somewhat universal JTAG adapter:

enter image description here

And finally this is likely exactly what you are looking for:

enter image description here

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I had the same problem recently. I used some of these breakout cables...

10-pin IDC Socket Rainbow Breakout Cable

Essentiall just bring the JTAG out to individual connectors no matter the pitch.

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The standard ARM 20-pin one doesn't have 20 unique pins. For example there are multiple ground pins. That's how they can get away with a 10-pin connector.

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  • \$\begingroup\$ Thank you for pointing this out. I added the schematics for my board's JTAG connector in my question. It looks like it needs more than 10 pins, because it uses MBED interface. \$\endgroup\$
    – 71GA
    Nov 27, 2015 at 18:36
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You could take the small cable from the connector on the LPC4088 and cut one of the connectors off. Then slit the wires of the flat cable apart to solder onto connector pin tails of a connector like this:

enter image description here

After the wires are all attached you could pot the connections in hot melt glue or epoxy.

I have made similar type adapters in the past albeit for a different type of application. Here is a picture of one such.

enter image description here

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  • \$\begingroup\$ Hahahaha. I was thinking of doing something like this myself but never thought of epoxy. =) Still I'd perfer to design a PCB to make the transition from the small pitch to large pitch. But ideal would be to just not waste my time and buy one. \$\endgroup\$
    – 71GA
    Nov 27, 2015 at 19:03
  • \$\begingroup\$ Well the urgency of need often drives the solution. Adapters if available can also be expensive because they tend to be low volume devices. Clearly if time, both expended effort and time duration are not critical factors then making a PC board and building an adapter is a better solution if you cannot find a commercial solution. \$\endgroup\$ Nov 27, 2015 at 19:08

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