NRF52840 USB Dongle - Failed to power DAP

[thanosPr]

Hello Guys,

I am facing an issue with nrf52840 usb dongle.

I am using an external debugger J-Link for debugging the target ic.

During development, i have succesfully made gatt peripheral for reading temperature/humidity with my own driver using zephyrOs.

I was ready to test a new development usb dongle for low power mode but debugger prints an error : "Failed to power up DAP". So, i came back to first one and debugger prints again the same error!

What is causing that issue??

Thanks in advance

[Jørgen Holmefjord]

Hi,

Which external debugger are you using to debug/program the Dongle?

If you did a "eraseall" operation on the Dongle with a debugger, the GPIOs of the chip will run at the default REGOUT0 voltage, which is 1.8V. Some debuggers (including the debug chip on the nRF5x DKs) does not support level translation, so the target needs to run at the same voltage as the debugger (3.0V on our DKs).

You can read more about this in the nR52840 Dongle programming tutorial.

Best regards,
Jørgen

[thanosPr]

Hi Jorgen,

Thank you for your quick response.

Here is my J-Link debugger.

I have not made an eraseall command to the target.

I measure 3.0V on Vout pin on usb dongle, does that mean that REGOUT=3V right?

Reset pin is held high no problem about this.

Could you please guide me to other possible solution?

[thanosPr]

According to the guidelines in your forwarded post, i modified the dongle in order to be supplied from external source and everything work!

To sum up, this behaviour is caused from on the on chip regulator / erase command?

[Jørgen Holmefjord]

Yes, that is likely the explanation if it worked with external supply.

However, I would have expected VDD OUT to read 1.8V, as this is connected to the VDD pin, which is the output of the REG0 regulator. This should be running at the voltage configured in REGOUT0 register.