Power Supply; Shutdown Enable Mode - Sferalabs Iono Pi Max v2 3+ Lite User Manual

Each LED has controllable general brightness, and independent brightness control of the
primary red, green and blue colors. The sysfs control files are l<n>_br, l<n>_r, l<n>_g and
l<n>_b in the led/ directory (I2C control registers 105-108, 110-113, 115-118, 120-123,
125-128 for CAN, RS-485, RS-232, USR and PWR).
When the user changes any of the control registers, that specific color or brightness level
is released for exclusive user's control, and will not be driven again, until the
microcontroller is reset, to provide the default indications.

Power supply

The power supply input voltage and current can be monitored reading files power_in/
mon_v, in mV (I2C control register 145), and power_in/mon_i, in mA (I2C control register
146).
Note that, when Iono Pi Max is being powered by the UPS battery, power_in/mon_v reads
a voltage value close to zero, while power_in/mon_i returns the current drawn from the
battery.
You can start a delayed power cycle by rising the Compute Module GPIO18 pin, writing 1
to the power/down_enabled file.
The timing and behaviour of the power cycle procedure are controlled by several
configuration parameters, described below.
After being powered off, Iono Pi Max will supply power to the Compute Module only when
the main power source is restored (the power-up mode parameter can change this
behavior, so that Iono Pi Max will always power up the Compute Module after a power
cycle, even when powered by the battery).

Shutdown enable mode

Set the shutdown enable mode.
In the default mode, the power-cycle is activated rising the Compute Module GPIO18 pin.
In the alternative "arm mode", setting GPIO18 high will arm the shutdown procedure, but
will not start the power-cycle until GPIO18 goes low. After the line goes low, the Iono Pi
Max controller will wait 60 seconds (configurable with the shutdown wait time parameter)
and then power off the Pi board for at least 5 seconds (configurable with the power-off time
parameter).
Note that, if the watchdog is enabled in "arm mode", it will remain active while GPIO18 is
high (armed).
Using the alternate "arm mode" a shorter shutdown wait time could be configured, then
GPIO18 set high immediately before starting the OS shutdown procedure. The GPIO18
pin should go low automatically when the CPU is halted, so that the power cycle will occur
shortly after. If the shutdown procedure fails to complete, the watchdog will still intervene
to prevent an indefinite lock.
The shutdown enable mode is configured with the power/down_enable_mode file (I2C
control register 36).
34 Iono Pi Max User Guide