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Using nRF52840 DK P19 to program nRF52840 that will run in High Voltage Mode

Michael

I have previously had success with programming the nRF51 Series using the nRF51 DK and want to use the nRF52840 DK to program a nRF52840 that will be run in High Voltage Mode. After connecting my nRF52840 DK to a PC via USB connector J2 do I externally power my nRF52840 to 3V and connect my VTarg to VDD or do I power to 5V and connect my VTarg to VDDH? This link has the closest answer to my question but I find Simonr's answer confusing. He says that the chip can be programmed using a USB supply, but while a voltage regulator converts that supply to 3.3V, outside the chip the voltage will still be 5V. Also, while the DK is powered at 5V via J2 the User Guide seems to imply VDD is the 3V produced by the default regulator. His answer did mention that you don't have to short VDD to VDDH for programming which would be a hassle. I would like some clarity on where I should connect VTarg (Pin 1 of P19) to and what voltage that net of my circuit should be running at for programming. I think clarity on this issue would be beneficial in a new User Guide if Nordic does decide for some revision at some point in the future.

  • +1

    Hi,

     

    As I understand it, the thread to which you link discusses applying the 5V rail from the USB cable to supply both VBUS and VDDH. From VDDH, there is an adjustable regulator internally which supplies VDD, which is the main power supply rail in nRF52840 and which sets the logical high level of the IOs. The challenge here is that the default output voltage at VDD, when supplied using VDDH, is 1.8V. This can be changed by writing to the UICR.REGOUT0 register, but as the debugger used does not support VDD=1.8V, VDD is supplied with 3V when programming the device for the first time. REGOUT0 is retained so as long as you do not erase UICR it you only need to set it once.

    Vtarg should always be connected to VDD, though as mentioned if the supply is at VDDH this can cause trouble. Some potential ways to workaround:

    • Use a debugger that supports 1.8V Vtarg.
    • Socket programming of your SoCs before assembly
    • Make a debugger adapter that shorts VDDH and VDD if VDDH < 3.9V.
    • Supply VDD directly when programming the first time.

     

    Best regards,

    Andreas

  • 0 in reply to Andreas

    Thank you for clarifying that quickly and thoroughly Andreas. I will be following the nRF52840_qiaa reference layouts where all VDD pins are connected so I will supply 3.0V to that net directly when programming.

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