£15.99 each (including VAT:
The Com Pi from AB Electronics is a communication add-on board for the Raspberry Pi supporting RS232 and 1-Wire® protocols. A 5V buffered I2C port is also provided on the board.
The RS232 port is connected to the UART port on the Raspberry Pi using a MAX3232 interface. The MAX3232 IC converts the 3.3V UART port to RS232 voltages allowing communication with RS232 compatible devices over a DB9 serial cable or with the use of a null-modem cable the board allows terminal access with linux on the Raspberry Pi using a terminal application. The RS232 port can be accessed through the DB9 port or the solder points on the PCB.
The 1-Wire® port is based around a DS2482-100 I2C to 1-Wire® bridge device. The DS2482-100 provides bi-directional protocol conversion between the I2C port on the Raspberry Pi and any attached 1-Wire® slave devices. An ESD Protection Diode is used to protect the Com Pi and Raspberry Pi from electrostatic spikes on the 1-Wire® port. Connections to the 1-Wire® port can be made through the RJ-12 socket or the solder points on the PCB. Wiring diagrams for the RS232 and 1-Wire® ports can be found on the Com Pi datasheet.
A 5V input port is also provided allowing you to use an external power supply on the 1-Wire® interface, reducing the load on the Raspberry Pi. If you choose to use the external 5V input please remove the jumper on the board to isolate the Raspberry Pi 5V bus.
Com Pi Datasheet
DS2482S (1-Wire Interface)
MAX3232E (RS232 Interface)
Vdd (5V input pin): 5.0V
Maximum current on 1-Wire pins: ±20 mA
I2C SDA/SCL voltage: 5.0 V
I2C port current: 100 mA
Click to download schematic PDF.
Click image to enlarge
The Quick2wire lib from https://github.com/quick2wire/quick2wire-python-api allows easy access to the I2C port via Python.
Configuring the RS232 communication on the Raspberry Pi
Configuring and using the 1-Wire® port on your Raspberry Pi
Using the Serial Port
OWFS (One Wire File System) with I2C support on Raspberry Pi
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