P-NUCLEO-WB55 USB dongle SB4 external power confusion

[NicRoberts]

From the manual for the P-NUCLEO-WB55 USB dongle

By default, the embedded STM32WB55RG microcontroller is supplied by 3V3, but the board offers another possibility to supply the device through the extension connector. The 3.3 V can first come from the USB and the LDO (5 to 3.3 V). Moreover, STM32WB55RG can be supplied by an external source, between 1.8 and 3.3 V. If the USB connector cannot supply the MCU, it is necessary to turn SB4 OFF and connect a power supply to the extension connector (pin 6 of the CN1 connector).

 

So when I look at SB4 on the board it looks like it is unbridged, see pic below. Does this mean its off? If so how come I can still power it through the USB-LDO 3V3 route? I would like to power through the connector so I can gauge how much current its drawing without USB connection.

 

 

[Andrew Neil]

when I look at SB4 on the board it looks like it is unbridged

 

That looks like a zero-ohm surface-mount “resistor” to me - so it is bridged.

 

PS:

example: https://au.element14.com/multicomp-pro/mc0805s8f0000t5e/res-0r0-1-0-125w-0805-thick-film/dp/2309112

 

Perhaps check the BoM ?

[NicRoberts]

Ahh right there is actually something there that I need to remove or can I hook up an external 3V3 as long as the USB isn’t connected & leave it be?

[Andrew Neil]

Ahh right there is actually something there that I need to remove 

I think so - a bit hard to tell from the photo.

 

PS:

Looks like SB2 is similarly closed ?

SB3 & 6 are open