Coreink power hold - #106
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CoreInk latches its own power rail on with GPIO12. Out of reset that pad is an input, and nothing in this firmware drives it until M5GFX's board autodetect does so as a side effect of M5.begin() - measured ~2000ms after reset. On battery the rail is held up by nothing at all during that window, so the board switches itself off after any reset, and powering it on means holding the power button down for two seconds or more instead of pressing it. Drive the pin from a MICROPY_BOARD_STARTUP hook, which app_main runs before creating the MicroPython task. Measured on hardware, reset to latch asserted: stock ~2000ms M5Stack factory Arduino build ~400ms this hook ~980ms M5Unified already asserts a hold pin this way for the Timer Cam in Power_Class::begin(); the CoreInk branch of that switch sets ADC and wake pins but never touches power_hold. 980ms is not yet short enough on battery - see the following commit.
With the startup hook in place the power-hold latch is still not asserted until ~980ms after reset, because the bootloader SHA-256s the whole ~3.4MB app image before app_main is reached. That is spent entirely before any application code runs, and on battery it is long enough for the rail to collapse. Deep-sleep wakes already skip validation (BOOTLOADER_SKIP_VALIDATE_IN_DEEP_ SLEEP=y), so the normal wake path never paid this cost - only resets did. Skipping it on power-on as well brings the latch to 50ms after reset. Verified on hardware, running on battery: a machine.reset() loop counting in RTC memory reboots indefinitely, where on stock firmware the board switches off at the first reset and stays off until USB is connected. This board has a single factory partition and no OTA slot, so a failed validation was never recoverable anyway.
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