Why I cannot download firmware into my 52840? USB cable is the only power supply.

[ndc_bee]

I connect VBUS to VDDH, and use a USB cable for power supply(high voltage mode), but I cannot download firmware into the 52840.

Unless I power the 52840 from the VDD pin, why?

My cricuit as below:

[Øyvind]

Hello, 

Can you give me some more details? You can't download if powered by VDDH, but you can download if powered by VDD? How are you connecting to your device to download/program it?

Kind regards,
Øyvind

[ndc_bee]

I just heard that the 52840 has 2 versions, C version and D version. and the C version has problems on VDDOUT function?

Is that mean C version cannot use high voltage mode?

[Øyvind]

I can't find anything about this. Where have you heard this? Can you provide a link?

There should not be any issues with programming when powering the board with USB to VDDH. Have you measured the voltage on your device when powered by USB?  

[ndc_bee]

I think I have found the root couse, when I power the 52840 from VDDH by a USB cable, the VDD voltage is only 1.8V, 1.8V is not enough to burn the firmware into the chip?

[Øyvind]

That would explain it. Please try to configure REGOUT0 to 3.3V. More information found in the Main Supply chapter.

Kind regards,
Øyvind

[ndc_bee]

I realize this, but the REGOUT0 is default output 1.8V, if I cannot download firmware at first, how could I configure it to 3.3V?

now our prototype is designd with high voltage mode powerd by a USB cable, and I didn't design test point for the VDD, this mean if I want to download firmware into the chip, I must power the chip from the VDD pin with 3.3V by soldering a jumper, this is very inconvenient.

The default output voltage dose not support firmware downloading is incomprehensible. Or I have some misunderstanding about this?

Do other customers have no such troubles?

[Øyvind]

This is a common issue if users are programming via a DK. This is too low to be used with the onboard programmer on e.g. nRF52840 DK. If you have an external programmer i.e. Segger JLink, it will support programming down to 1.8V