Firmware testing
----------------

Situations/features to test:

- factory firmware
  - USB debugging
    - is disabled by default after start
    - can be enabled/disabled at runtime
      - via I2C
      - if Pine + F + U is pressed  (status is reflected over I2C
        in a control register)
  - scanning block works
    - switching it on/off works at runtime
    - no interrupts are fired when blocked
    - no keys appear pressed during a block
  - USB bootloader jump works
    - if Pine + F + B is pressed
    - via USB debugger mode
    - via I2C command
  - reset over I2C works
  - I2C debug log readout works
  - selftest works
    - shows result via I2C debug log
  - exposed GPIOs are accessible over I2C
    - direction configuration works
    - readout/setting works

- interrupt
  - 10us pulse visible on logical probe capture
  - POGO interrupt is received on the SoC

- charger
  - I2C A communication works
  - I2C A timeout mechanism works when the bus is blocked

- user firmware
  - flashing works
  - reading works
  - deletion works
  - is not jumped to unless it's commited after flashing
  - can be executed
    - starts automatically unless Pine+F+H is held on powerup