Disable 3V3_S toggle via IO2

When using a RAK19007+RAK4631, is it possible to disable the toggle of 3V3_S power rail via IO2? I would like to use IO2 as a general purpose IO, for example as a user button, LED, vibration motor, etc.

Is is possible to set IO2 to not do this, so it can be used in the same manner as IO1 or IO3-IO8?

I imagine I could use a transistor such as 2N2222 and avoid shorting IO2 to GND, using it as a trigger to power the component connected to the emitter leg of the transistor. I have done this to power components like vibration motors and passive piezeo buzzers that require more current than the GPIO pins can provide. That’s another issue though :slight_smile:

Thank you,

How to disable IO2 to control 3V3_S depends on your version of the RAK19007.

On the RAK19007 Ver.B IO2 controls a transistor/mosfet combination:
Location of Q7, Q8, R20:

On the RAK19007 Ver.C IO 2 controls the SGM2578 power switch:
Location of R23:

Thank you! I have Ver.C; how would I disable IO2 to control 3V3_S?

Also same question for Ver.B in case I have any of those older revision boards…

On Ver.C boards remove R23, the STM2578 has an internal pull-down. 3V3_S will be always off.

On Ver.B its more complicated, I guess you need to remove Q7 and Q8 and either connect Q7 pin 3 to GND or 3V3.

I see. However I would prefer to have 3V3_S always on. Given you suggestion, I would then need to remove R23 on Ver.C boards and bridge 3V3 from somewhere else like VDD pin to provide power to 3V3_S. Would that be accurate?

Also is this impossible to do via software, to keep disable 3V3_S toggle but keep 3V3_S always on?

Thank you for answering my questions!

Not a good idea. The 3V3_S on the Ver.C boards is an output of the SGM2578.
I would rather remove R23 and shorten B2 to 3V3.

And on the Ver.B I would remove Q7, Q8 and R20 and then shorten pins 2 and 3 of Q7.

Regarding keeping 3V3_S via software without using IO2, that is not possible.

Thank you, this was suggested by someone else and since that it microsurgery that I cannot hope to do myself I will just have to put away my idea to use IO2 without toggling 3V3_S power. I sincerely appreciate your suggestions and expert technical assessments!


If you need larger volumes, like 200 RAK19007, you could send an inquiry to our sales [email protected] and we could look into a custom version for you.

Thank you, I will seriously consider this. I regularly buy many RAK19007s and this would be very convenient for my needs.