debbuging custom board 1.8V powered with nrf52840 DK

[julienh]

Hi,

I tried to debug my custom board with NRF8240 DK and use JLINKRTTViewer but I'm not able to connect to it. 

I'm able to program the external board using P20 and VDD provided by the dev kit. I'm also able to debug with JLINKRTTViewer just after programming the board. The problem is that on my custom board, the nrf52840  is powered with 1.8V power supply and during programming, I disconnect a jumper on my board to avoid any issue when programming directly with the higher VDD voltage DK (3V). 

When I start powering my board with the internal power supply and connecting VTG to my power (1.8V), I'm not able to connect with JLINKRTTViewer "ERROR: Could not connect to target device."
I tried to wiring : 

-SWDIO / SWDCLK are connected. GND are connected together and also GND_detect. VTG is connected with a jumper to Vdd or Vdd_nrf to force external debugging. 

- SWDIO / SWDCLK are connected. GND are connected together and also GND_detect. VTG is connected to the 1.8V power on my board. 

Is that possible to debug a 1.8V external NRF52840 when NRF52840 DK is powered by USB ? 

[Jared]

Hi,

Is that possible to debug a 1.8V external NRF52840 when NRF52840 DK is powered by USB

 No,  you need to make sure that the voltage on the DK and the custom board is the same. This means that if you're using USB then the external board should be supplied with 3V. 1.8V debugging is not supported by the DK. You should use a stand-alone J-link debugger instead

regards

Jared 

[julienh]

Hi Jared,
Do you have any reference to recommend ? I saw jLINK base but it's 400$ so if I can find a cheaper solution, would be great.

PS : I saw this on other topics http://embeddedsoftdev.blogspot.com/p/ehal-nrf51.html but I can't find if we are able to use J-link RTT Viewer or if there is any equivalent to debug with RTT ? 

Thank you

[Jared]

Hi,

We don't generally give out recommendations on third-party products., but I've seen customers use this SEGGER J-link before.

I would consider contacting either SEGGER or your distributor and ask them. 

regards

Jared