nrf52 preview DK debug out for custom design

RE: nrf52 preview DK debug out for custom design

Lakerno — Sun, 13 Sep 2015 03:34:08 GMT

Oh ok. I will get a jlink edu then. Thanks for the input

RE: nrf52 preview DK debug out for custom design

RK — Sun, 13 Sep 2015 02:29:43 GMT

The segger in this case is a JLink OB. This is one of Segger's more recent offerings. It has the benefit of being low cost because it's just a port of Segger's stable JLink software to various MCUs which have on board USB, like the SAM3U which (I think) is the one on the Nordic boards. However it's a 1-chip solution so the OB needs to be powered up enough to run its USB interface and that limits the GPIO input/output/sense voltages to around 3V as well. It's the GPIOs on the SAM3U which run the SWD interface, directly.

The 'real' Seggers are somewhat more complicated and have fully buffered JTAG/SWD lines which work down to a much lower voltage. They basically level-shift internally.

If you need to test at 1.8v, you need a real Segger, like the JLink EDU. Does nobody at NUS have one you can borrow?

RE: nrf52 preview DK debug out for custom design

Lakerno — Sat, 12 Sep 2015 06:27:17 GMT

"but I don't think the Segger will be able to drive the USB signals with just 1.8V. " I am not sure, if I understand what you said. I want to use the the nrf52 preview dk to debug a board, which uses 1.8V power supply. May I check why segger need to drive USB signals?

What is the standard method, instead of using level shifters etc, which is troublesome.

RE: nrf52 preview DK debug out for custom design

MartinBL — Fri, 11 Sep 2015 14:51:58 GMT

I believe this is because

You need USB to connect the Segger chip to your PC.
When a USB cable is connected the supply voltage on your board will be regulated to ~3.0 volts.

You might be able to cut the power from the USB cable and supply the board with 1.8V from a different supply, but I don't think the Segger will be able to drive the USB signals with just 1.8V. Hence you will need a level shifter or find a different way.