DFU and chip resets

[inyourface]

Hi 

We are working on the secure DFU. The issue is that the NRF52832 chip resets when switch to the DFU mode. All the GPIOs are turned off during reset. However, one of the GPIOs is to turn on the main regulator in order to power on the board. 

How to keep the GPIO always on during the DFU process? I set the GPIO on in the bootloader and application but it still turns off when switching to DFU mode. 

Thanks,

Face

[Jørgen Holmefjord]

Hi,

How do you initially power the board if the main regulator is turned on by the chip itself?

The state of the GPIOs are undefined during reset. If you need the pin in a specific state during reset, you need to add an external pull resistor.

Best regards,
Jørgen

[inyourface]

Jorgen,

There is a button to turn on the main regulator initially and then the GPIO takes it over. 

Is there a way to set the GPIO high during the DFU process in the firmware?  Does the DFU have to reset the chip ?

[Jørgen Holmefjord]

I see.

inyourface said:

Is there a way to set the GPIO high during the DFU process in the firmware?

If you mean during reset, there is no way to do that without external components. The GPIO state is always reset by a system reset. You could try to configure the GPIO at the very beginning of the bootloader main (or even SystemInit), but I'm not sure if this is fast enough or reliable.

inyourface said:

Does the DFU have to reset the chip ?

Technically it should be possible to branch to the bootloader, instead of using a system reset to enter it, similar to how the application is entered from the bootloader. See this answer.