How to separate nrf52dk target and probe power bus?

[butch]

On the nrf52dk development kit, I want to power the target nrf52 from an external supply without powering the interface mcu (the debugging probe). How do I wire that? I don't want to measure the current, or debug, I just want to separate the power busses.

My best guess is to 1) turn the "Power" slide switch off 2) cut SB9 and 3) connect my power supply to net Vdd_nRF (on either pin 1 of P20 or pin 1 of P22.) Should that work?

(Fig. 2 "Power Supply Circuitry" for the nrf52DK shows that net Vdd_nRF is connected to net VDD by R6 but looking at the board, R6 is not populated.)

Fig. 2 also shows that SW6 also switches net V5V to net VBUS, but I don't know for sure which of those nets is the power supply to the interface mcu and which is power from the USB cable. Alternatively, if I leave the PowerSwitch in the On position, I could connect my power supply to "External supply" connector P21 if I am then careful to not connect the USB cable? (And the debugger probe would not be powered?)

(A related question is: could I connect DebugOut and DebugIn with a JTAG cable and still use the separately powered debugging probe to flash and debug the separately powered target? I haven't studied that much, but it looks like that is not possible, the cable would be parallel to the hardwired SWD and UART nets between the two.)

[Jørgen Holmefjord]

Hi,

You can download the hardware files for the nRF52-DK here. This includes all schematics for the board. On sheet two of the schematics, you can see that the interface MCU is powered by VDD through SB29. Cutting SB29 will disconnect the interface MCU. You can then power your board through External Supply (P21).

There is no JTAG, but you can connect an external debugger that support the SWD interface to the Debug in port (P18), to flash and debug the nRF52832 IC.

Best regards,

Jørgen

[butch]

Looking at the schematic, the LED's on the radio are powered from VDD. So my first solution probably was powering the radio, but the LED's had no supply and so did not flash. So another suggestion for the next DK: at least one LED that is powered by VDD_nRF.

(I could just buy a separate radio module. But I bought a BMD-300 having neither an LED nor a 32khz crystal. And I bought a BLE Nano whose nRF51 has a different ADC. Which is why I am trying to isolate the radio on the DK.)