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SUPER-WATCHDOG WITH BATTERY BACKUP FOR RASPBERRY PI

www.sequentmicrosystems.com

USER'S GUIDE VERSION 2.0

GENERAL DESCRIPTION ................................................................................................................................. 2

BOARD LAYOUT ............................................................................................................................................. 4

BLOCK DIAGRAM ........................................................................................................................................... 4

POWER REQUIREMENTS ............................................................................................................................... 5

SPECIFICATIONS ............................................................................................................................................ 5

SOFTWARE SETUP ......................................................................................................................................... 6

PROGRAMING THE WATCHDOG ................................................................................................................... 8

Summary of content (9 pages)

PAGE 1
SUPER-WATCHDOG WITH BATTERY BACKUP FOR RASPBERRY PI www.sequentmicrosystems.com USER'S GUIDE VERSION 2.0 GENERAL DESCRIPTION................................................................................................................................. 2 BOARD LAYOUT ............................................................................................................................................. 4 BLOCK DIAGRAM ....................................................................................
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GENERAL DESCRIPTION The Super-Watchdog for Raspberry Pi B+, 2, 3, 4 and Zero provides the safety required by mission critical projects, implementing two major functions. It power-cycle the Raspberry Pi in case of software lock-up, resetting not only the Pi but also any peripheral attached to it, and it prevents SD-Card failure in case of power loss, by allowing the Raspberry Pi to shut down itself safely.
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Raspberry Pi needs to issue a reset command before the timer on the watchdog expires. The command can be sent either on the I2C port , or by toggling GPIO11 ( Pin 23 on the GPIO connector). The timer period after power up and the active timer period can be set from the command line. The number of resets is stored in flash and can be accessed or cleared from the command line. When running on battery power, the watchdog processor monitors the battery voltage.
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BOARD LAYOUT BLOCK DIAGRAM 4
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POWER REQUIREMENTS In order for the watchdog to cycle the power to Raspberry Pi, +5V power needs to be supplied only to the watchdog. The watchdog has two power connectors: USB connector on bottom and 2.1mm barrel connector on top. The USB connector can supply up to 1.5A, while the barrel connector up to 2A. If your Raspberry Pi system requires more than 2A, you need to supply power to both connectors. If the 5V power supply fails, the watchdog switches the power supply to battery.
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SOFTWARE SETUP The Pi-DOG board occupies the I2C address 0x30. 1. Have your Raspberry Pi ready with the latest OS. 2. Enable I2C communication: ~$ sudo raspi-config 3. Install the wdt software from github.com: ~$ git clone https://github.com/SequentMicrosystems/wdt-rpi.git ~$ cd /home/pi/wdt-rpi ~/wdt-rpi$ sudo make install ~/wdt-rpi$ wdt The program will respond with a list of available commands. Type "wdt -h" for online help.
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After installing the software, you can address the watchdog with the command "wdt". The watchdog will respond with a list of available commands. Any command send to the watchdog will reload the watchdog timer. wdt -r[eload]: reload watchdog timer, prevent Raspberry power cycle. wdt - d[efault]: set the default watchdog timeout (seconds). The watchdog loads this value after a power cycle. This value needs to be long enough for the boot process to complete.
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PROGRAMING THE WATCHDOG After the first power up, the watchdog cuts off the power to Raspberry Pi, performs a self-check and tries to turn on the power. The watchdog monitors the input power, the battery power and the power supplied to Raspberry Pi. If a hardware error is detected, the watchdog flashes rapidly (5 times per second) the on-board LED. If no error is detected, the LED flashes 1 time per second and the watchdog enters the stand-by state, waiting to be activated.
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gpio -g mode 11 out while : do gpio -g toggle 11 sleep 60 done 3. RESET THE WATCHDOG FROM CRON Create the wdt_reload with the following content: #!/bin/sh /home/pi/wdt-rpi/wdt -r Make it executable, then edit the crontab file: ~/wdt-rpi$ crontab -e Add the following line at the end: * * * * * /home/pi/wdt-rpi/wdt_reload Save the crontab file.