Using Strato Pi UPS
Real Time Clock
Strato Pi UPS has a hardware real time clock with a dedicated long-life non-rechargeable
back-up battery.
Once the RTC modules and configuration files are properly installed, you will simply use
the date and time commands to control the hardware clock.
Serial port
Strato Pi UPS uses the Raspberry Pi standard UART TX/RX pins on the GPIO connector
to implement a standard serial port with support for both RS-232 and RS-485.
Simply connect the RS-232 RX, TX and GND lines to the RS-232 posts of the Strato Pi
terminal block or the RS-485 A, B and GND to the RS-485 posts of the terminal block.
Never connect both RS-232 and RS-485 lines to Strato Pi. Strato implements a single
serial port, not two.
Both interfaces are isolated from the Raspberry Pi’s serial lines using dedicated opto-
couplers and from the main power supply with a high-efficiency DC-DC converter. This
configuration should prevent ground loops between devices connected through the serial
lines.
The RS-485 TX/RX switching is implemented automatically in the Strato Pi’s micro-
controller, based on speed and number of bits detection, and is completely transparent to
the software controlling the UART on Raspberry Pi.
The RS-485 line has 620 Ohm pull-up and pull-down resistors on lines A and B. The
biasing resistors ensure that, during idle periods the data lines are kept at a stable voltage
level and prevent false triggering of receiver input.These resistors can be disabled by
removing jumpers JP1 and JP3 respectively.
A 100 Ohm termination resistor between A and B can be enabled installing jumper JP2.
RS-485 JUMPERS SCHEMATIC
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Strato Pi UPS User Guide
