Upcycle your ATX desktop power supply, reduce cable clutter, and power your Compute Module 4 based projects all while aiding in preventing the corruption of valuable disk files through soft power shutdown. Additionally, the ATX Watchdog for Compute Module 4 comes with a configurable watchdog timer and power management..

Specifications:

• Features soft shutdown and reboot of the Compute Module to minimize disk file corruption
• Includes configurable watchdog timer to power cycle the I/O board in case of Compute Module freeze
• Includes configurable power management to automatically restart the Compute Module after a power failure
• Works with most inexpensive off the shelf ATX desktop supplies using 20 or 24 pin ATX connectors
• Mounts directly onto the GPIO header of the I/O board
• Screw terminals break out +12 VDC and +5 VDC for user projects. The screw terminals are rated for 3.0 amps
• Provides 12VDC supply at up to 3 amps to the I/O board
• PCB is 1oz copper with lead free HASL finish
• Conforms to the Raspberry Pi Foundation's HAT footprint.
• Choice of 40 pin GPIO 8.5 mm non-stacking or 11.65 mm stacking header. Stacking header allows use of other add-on boards or HATs.
• Comes as a DIY kit to keep costs low or fully assembled.

Operating Modes

• Turning on the ATX Power Supply: Turning on/plugging in the ATX power supply will supply a trickle voltage to the microcontroller on the ATX Watchdog. The ATX Watchdog will flash the power and Boot Ok LEDs in rapid succession to indicate the board is powered up and functioning.

• Power up the Compute Module: Depressing the power switch when the Compute Module is turned off will initiate the power up sequence. The power indicator LED pulsates slowly until the Boot Ok command is received from the Compute Module. When the Boot Ok command is received, the Boot Ok LED lights and the power LED goes steady on.

• Reboot: Depressing the power switch for greater than a half a second and less than three seconds while the Compute Module is on will initiate a reboot of the Compute Module. The power LED dims and the shutdown LED pulses once to signal the Compute Module to reboot. When the Compute Module starts to reboot, it sends a command to the ATX Watchdog to turn off the Boot Ok LED. The power LED will then pulsate until the Compute Module has rebooted and the ATX Watchdog receives the Boot OK command. The power and Boot Ok LEDs will then go steady on.

• Shutdown: Depressing the power switch for over three seconds while the Compute Module is on will initiate a shutdown of the Compute Module. The power LED dims and the shutdown LED goes steady on to signal the Compute Module to shut down. When the Compute Module shuts down, it sends a command to the ATX Watchdog to turn off the Boot Ok LED. The ATX Watchdog will then wait a long enough period of time for the Compute Module to perform a clean shutdown before turning off power to the Compute Module.

• Hard Shutdown: In the event that the Compute Module has frozen and is not responsive to commands from the ATX Watchdog or user interaction, you may force the ATX Watchdog to power off the Compute Module. Depressing the power switch for greater than ten seconds will power off the Compute Module.

• Command line or Application Forced Shutdown: The ATX Watchdog has the ability to detect when a shutdown or reboot is initiated from the Compute Module. When the user selects “Shutdown” or “Reboot” from the “Logout” menu, for example, the Compute Module sends a command to the ATX Watchdog to turn off the Boot Ok LED and to wait a configurable amount of time. While it’s waiting, the power LED will pulsate. If the Compute Module successfully reboots, it will command the ATX Watchdog to turn on the Boot Ok LED. If the Compute Module does not reboot, for example the user initiated a shutdown, then the ATX Watchdog powers off the Compute Module.

• Power Management: The power management option directs how the ATX Watchdog responds to power failure. In the event the power fails, the default mode of the ATX Watchdog is keep the Compute Module powered off. Optionally, you can configure the ATX Watchdog to power on the Compute Module after a power failure.

• Watchdog Timer: The ATX Watchdog has the option of power cycling the Compute Module in the event the Compute Module freezes for some reason and can no longer communicate with the ATX Watchdog.

• Reset Default Values You may, at any time, reset all edited parameters to their original values.

Why did you make it?

ATX desktop power supplies provide voltages and currents not available with your typical Raspberry Pi wall wart. People building retro arcades, model railroading layouts, etc... often find a need for 12 VDC and 5 VDC at higher currents in addition to being able to soft shutdown their Raspberry Pis. This board fulfills this need all while being easy to use and affordable.