nRF52840 High Voltage mode with external JTAG from 52840-DK

[sprhawk]

When custom board with nrf52840 uses High Voltage mode DCDC, in default mode, ( no firmware ), the VDD should be 1.8V as default value in REGOUT0,

However the Voltage Level from JTAG from a 52840-DK is 3.3V, is it ?

As a result, I cannot uses this external DEBUG OUT from DK  ? Is my understanding correct ?

[mathiaso]

Hi.

Just to make sure, you have a custom board in High voltage mode with the default VDD voltage of 1.8V (set in REGOUT0) and want to program it using the nRF52840 DK, as described here?

Best regards,
Mathias

[sprhawk]

That is correct.

( I think the VDD voltage is set to 1.8V by default when running in High Voltage mode, right ?)

[mathiaso]

sprhawk said:

I think the VDD voltage is set to 1.8V by default when running in High Voltage mode, right ?

Yes, that is described in the REGOUT0 register description I linked to earlier.

In the description of the nRF52840 DK debug output, which I also linked to earlier, you can see that it is possible to set the VDD voltage in the firmware.

An alternative solution, if possible, could be to short the VDDH pin to VDD on your custom board when debugging, and then supply your custom board from the DK.

[sprhawk]

Understand.

Thanks