Internal Fan And Temperature Sensors; Analog Inputs - Sferalabs Iono Pi Max v2 3+ Lite User Manual

Watchdog default behavior is described below, but all timing parameters and control logic
can be modified through the I2C control registers and sysfs files.
The watchdog is normally disabled. To enable it, set GPIO39 pin to high. While GPIO39 is
high, the Iono Pi Max controller will watch for state changes of the GPIO32 heartbeat pin.
You should ensure that GPIO32 flips its state between high and low faster than every 60
seconds.
If the Iono Pi Max controller doesn't see GPIO32 changing state for more than 60 seconds,
it will initiate a shutdown procedure, rising the GPIO17 timeout pin to high, to signal that a
watchdog timeout has occurred.
If possible, you should immediately initiate a software shutdown on Raspberry Pi Compute
Module, and set the GPIO18 shutdown pin to high. When GPIO18 is set to high or 60
seconds after the timeout, Iono Pi Max will wait 60 seconds more, then power cycle the
Raspberry Pi Compute Module (removing all power supply sources to the Compute
Module, and at the same time pulling the RUN line low).
Note that Iono Pi Max will reset the Raspberry Pi Compute Module even if GPIO18 is not
set high. In this case the power cycles occurs 120 seconds after the heartbeat timeout.
All of the above watchdog features can also be controlled using the sysfs files under the
watchdog/ directory.

Internal fan and temperature sensors

Iono Pi Max has an internal fan to improve heat dissipation inside its DIN-rail enclosure,
particularly in the area of the power regulators, where most of the heat is generated.
Two temperature sensors, located on the top and bottom side of the main circuit board,
can be used to monitor the current temperature. The values, in °C/100, are available in the
read-only files sys_temp/top and sys_temp/bottom (I2C control files 155-156).
In the factory default configuration, the Iono Pi Max controller automatically starts the fan
when the internal temperature reaches 55 °C or power supply input power reaches 15 W,
and stops when temperature falls below 50 C and power supply input power becomes less
than 10W.
It is also possible to force the fan to run continuously writing 1 to fan/always_on (I2C
control register 137).
The fan status is available from read-only file fan/status (I2C control register 140).

Analog inputs

Iono Pi Max has voltage, current and Pt100/Pt1000 sensors analog inputs. All analog
inputs are galvanically isolated from the main power supply rail and all digital logic in Iono
Pi Max.
The AGND terminals are the ground reference for the analog inputs.
All these inputs are connected to a low-noise, high-resolution 24-bit analog-to-digital
converter, the Analog Devices AD4112, which is factory calibrated to achieve a high
degree of accuracy.
The Iono Pi Max controller's firmware takes care of the ADC configuration and reading,
returning the measured values in I2C control registers, and the corresponding sysfs files.
37 Iono Pi Max User Guide