Raspberry and I2C Interface

Raspberry and I2C Interface

For coupling the embedded Linux board to various types of devices, relays and sensors an expansion board is needed. Here you can find more information on how to do this.

I2C interface

With two wires it possible to address up to 1136 members. I2C is a synchronous bidirectional communication system that allows devices to transfer data using only two wires: a bidirectional data line (SDA) and a clock line (SCL).
Max clock rate: 400kHz.
The I/O board contains a PCA9555.

Three hardware pins (A0, A1, A2) vary the fixed I2C-bus address and allow up to eight devices to share the same I2C-bus/SMBus. The fixed I2C-bus address of the PCA9555, allowing up to eight of these devices in any combination to share the same I2C-bus/SMBus.

The PCA9555 is a Port-Expander with 16 GPIO-Pins, which can be controlled easily over I2C. Three device inputs (A0 - A2) determine the I2C address and allow up to eight I/O expander devices to share the same I2C bus. With a maximum of eight PCA9555 Port-Expanders the states of 64 inputs can be monitored and 64 outputs can be driven.

The first station with address number 0, corresponding to inputs and outputs 0.0 - 0.7 in a ladder diagram. The next station with address number 1, corresponding to inputs and outputs 1.0 - 1.7 in a ladder diagram, etc.

Hardware configuration with GNUBLIN Boards.

Raspberry Pi to Gnublin bridge

Usefull GNUBLIN board and modules

  • GNUBLIN-LAN With LAN, RTC and relay on board for network based applications.
  • The GNUBLIN modules-bridge enables the GNUBLIN to connect several modules simultaneously.
  • Simply get more input and output pins per port expander. Up to 16 GPIO pins per additional port expander.
  • GNUBLIN module-ADC provides 8 analog inputs (8-bit resolution).
  • Datasheet PCA9555



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