Custom E-ink driver board (UC8252c). Charge pump not starting: PWM is active, but MOSFET Drain is stuck at 3.3V. Hi everyone, I'm designing a custom driver board for a 2.13" E-ink display (controller UC8252c) driven by an RP2040 Zero via SPI. The digital logic seems to work perfectly, but the high-voltage DC-DC booster (charge pump) refuses to start. Here is the situation: * **Software/SPI:** Working. I send the init sequence, the image data, and the refresh command (0x17 + 0xA5). The display acknowledges the command by pulling the `BUSY` pin `LOW` and holds it there (waiting for voltages to rise). * **The Issue:** The screen stays white because the high voltages are not being generated. * $V\_{GH}$ reads 3.3V (should be +22V). * $V\_{GL}$ reads \~0.1V and drops slowly (should be -20V). **Measurements on the Booster Circuit:** * `GDR` (MOSFET Gate): 0.89V DC average. This means the UC8252c is correctly generating the high-frequency PWM signal to pump the inductor. * `Drain` (MOSFET Pin 3): 3.3V solid.…