unbrick switch on custom add-on board

[Gerhold Ten Voorde]

Hi,
We made our own add-on board for Voxl2. Now we want to add a switch, similar to SW2 on the Voxl2, to unbrick the board if needed.
I have seen that we can do it through pin 56 of connector J3. My questions:

• list itemis this pin high active or low active?

• list itemAre there resistors needed (like pull-up, pull-down, or in serie)?

• list itemIf it is high-active, should I use pin 47 of J3?

Thanks

[Vinny]

Hi @gerhold-ten-voorde
Yes, you are correct. Pin 56 is the signal "FORCE_USB_BOOT". It is default weakly pulled down by the SoC.
To enter eDL/QDL mode, this switch connects a 2-2.2K pullup to VREG_S4A_1P8 (J3 pin 47).
So, on M0154, the default OPEN/OFF position does noting, when ON it enables the pullup.
Hope that helps.
Thanks!
Vinny