Using Strato Pi CM
Real Time Clock
Strato Pi CM 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.
RS-485 serial port
Strato Pi CM uses the Raspberry Pi standard UART TX/RX pins on the GPIO connector to
implement a standard RS-485 port.
The RS-485 port is 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
line.
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. It can also be manually configured to
work with fixed communication parameters (speed, bits, parity, stop bits) or in passive
mode (refer to the "Strato Pi Logic Controller Advanced Configuration Guide" document for
additional information).
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 JP2 respectively.
A 100 Ohm termination resistor between A and B is connected when the J1 micro-switch is
moved toward the terminal block.
RS-485 JUMPERS AND SWITCH SCHEMATIC
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Strato Pi CM User Guide
