A 2.2A resettable fuse is also used to protect the battery input. When Strato Pi UPS works
under battery power, the maximum 5V current delivered to the Raspberry Pi should not
exceed 3.5A when the battery is fully charged.
Auxiliary power supply output
Strato Pi UPS has an auxiliary power supply output pin, labeled VSOUT, to power external
devices.
The aux power supply output is connected to the main power supply input, and switched to
the battery input when there is no power on the main power supply input.
It is not a regulated voltage output and should only be used to power devices that accept a
wide range power supply, compatible to both the battery voltage and the power supply
voltage you are using.
When Strato Pi UPS is turned off by the UPS controller while on battery power, the VSOUT
power supply output is also switched off until the main power supply is restored.
The maximum current drawn by the loads connected to VSOUT is limited by the current
drawn by the Raspberry Pi, the power supply or battery input voltage, and the 2.2A
resettable fuses that limit the total amount of input current.
Dedicated GPIO pins
Strato Pi uses some of the Raspberry Pi’s GPIO pins. These pins should not be used for
other functions.
GPIO pin
Direction
Description
GPIO2/SDA
I
2
C SDA line for the real time clock
GPIO3/SCL
I
2
C SCL line for the real time clock
GPIO14/TXD
out
serial TX line
GPIO15/RXD
in
serial RX line
GPIO5
out
cycle high/low for watchdog heartbeat
GPIO6
out
set to high to enable the watchdog
GPIO12
in
high on watchdog timeout
GPIO16
out
set to high to enable the shutdown cycle
GPIO20
out
set to high to sound the buzzer
GPIO26
in
high when on battery power
GPIO13
out
soft serial TX for Strato MCU configuration
GPIO19
in
soft serial RX for Strato MCU configuration
15
Strato Pi UPS User Guide
