This is a board for remote 8-input expander for I2C bus based on PCF8574. Making it ideal as an isolation input expander for I2C bus. It is designed to compatible with almost 2.5V to 5.5V microcontrollers.
The PCF8574 is the I2C bus controller which talk to microcontroller and then read status of input voltages from photocouplers. The PCF8574 supports 100kHz bus frequency. And they can be connected to 2.5V to 5.5V external logic voltage of I2C port of microcontroller.
The board has interrupt signal. On this line, the remote I/O can inform the microcontroller if there is incoming data on its inputs.
The board has 8 photocouplers for input voltages. Each inputs support 6V to 15V continuous input voltage and up to 30V for pulse input voltage. More than 15V of continuous voltage can be applied but need external resistor.
The board is addressed by 3 jumpers to make 8 different addresses. So that 8 boards can be connected together on one bus. Moreover 16 boards can be connected together on one bus when they have 16 different addresses. By this way, 8 boards of the PCF8574 and 8 boards of the PCF8574A can be connected together on one bus. Because the PCF8574 doesn't have same address as the PCF8574A.
The boards have inverse polarity protection circuit for power supply input voltage to prevent damage from a mistake of connection. The board has LED to show status of the power supply input voltage. The board has a small PCB size 28x81.5mm.
- PCF8574 I2C bus controller
- 8 Photocouplers
- Power supply input voltage 2.5V-5.5V
- 100kHz I2C bus frequency
- Address by 3 jumpers for use of up to 8 addresses
- Up to 16 boards on one bus
- Interrupt output pin
- Compatible with almost microcontrollers
- 6V to 15V continuous input voltage
- More than 15V can be, need external resistor
- Inverse polarity protection circuits
- Small board, PCB size 28x81.5mm