Normal state (Modchip GPIO = Low or floating):

R2 (10kΩ) pulls the gate of both M1 and M2 low.
Both MOSFETs stay OFF.
R3 pulls the RCM Point up to 3.3V.
Multimeter should read ~3.3V at RCM Point.

RCM Injection state (Modchip GPIO = High 3.3V):

GPIO drives the gates of M1 and M2 high.
M2 turns ON first → connects the source of M1 to ground through R1 (1kΩ).
M1 turns ON → strongly pulls RCM Point down to near 0V.
Multimeter should read ~0V (or <0.1V) at RCM Point.


The extra R2 10kΩ on the gate line is actually helpful — it acts as a proper pull-down, making the circuit even safer when the GPIO is floating.
The 1kΩ (R1) gives some current limiting and protection


How to Test It Safely with Multimeter
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Power the circuit with a stable 3.3V (use a good regulator or the modchip’s 3.3V output).
Connect your multimeter in DC voltage mode:
Black probe to GND.
Red probe to RCM Point.

Measure with GPIO low (connect GPIO to GND or leave floating) → should read ~3.3V.
Measure with GPIO high (connect GPIO to 3.3V) → should drop to ~0V immediately.
You can also measure at the gate of the MOSFETs to confirm they get ~3.3V when active.