nRF52 SWD programming interface

[Tosa]

I'm developing the PCB schematic for a system using the nRF52 and have some questions on the SWD programming interface.

1. It seems that I only need 4 pins for the Segger J-Link Base (VTREF/SWDIO/SWDCLK/GND), correct?

2. P0.21 is labeled as a RESET pin also; does the SWD programmer require access to this? If it is optional, what are the benefits to having it connected, and how do I enable the RESET functionality?

3. Since I don't need all 20 pins, I plan on using an adapter board such as the J-LINK 9-PIN CORTEX-M ADAPTER. But I also found the ARM-JTAG-20-10 which is 5x cheaper. The schematics seem the same for both, so can I use the ARM-JTAG-20-10 with the Segger J-Link Base? Why is there such a huge price difference if they are the same?

4. Are there any low cost programmers that support 1.8V (I'll have the nRF52 powered directly by a 1.8V supply)?

[Hung Bui]

Hi Tosa,

1. Yes, correct.

2. No, you don't need RESET pin to program/debug. You can do softreset if you don't have access to the RESET pin. RESET pin is optional on nRF52, you can actually disable RESET and use the pin as normal GPIO pin.

3. I think it's fine, as long as it connects the correct pins.

4. I actually don't know. Maybe someone here knows. Have you checked on Segger website ?