Arduino library for PCF8574 - 8 channel I2C IO expander
This library gives easy control over the 8 pins of a PCF8574 and PCF8574A chip. These chips are identical in behavior although there are two distinct address ranges.
| TYPE | ADDRESS-RANGE |
|---|---|
| PCF8574 | 0x20 to 0x27 |
| PCF8574A | 0x38 to 0x3F |
The library allows to read and write both single pins or 8 pins at once. Furthermore some additional functions are implemented that are a little more playfull but still are useful.
- PCF8574(deviceAddress) Constructor with device address as parameter.
- begin(val = 0xFF) set the initial value for the pins and masks.
- begin(sda, scl, val = 0xFF) idem, for the ESP32 where one can choose the I2C pins What needs to be added in the future is a parameter to choose another Wire interface as some processors have multiple hardware Wire interfaces.
- read8() reads all 8 pins at once. This one does the actual reading.
- read(pin) reads a single pin; pin = 0..7
- value() returns the last read inputs again, as this information is buffered in the class this is faster than reread the pins.
- write8(value) writes all 8 pins at once. This one does the actual reading.
- write(pin, value) writes a single pin; pin = 0..7; value is HIGH(1) or LOW (0)
- valueOut() returns the last written data.
- setButtonMask(mask)
- readButton8()
- readButton8(mask = 0xFF)
- readButton(pin)
- toggle(pin) toggles a single pin
- toggleMask(mask) toggles a selection of pins, if you want to invert all pins use 0xFF.
- shiftRight(n = 1) shifts output channels n pins (default 1) pins right (e.g. leds ). Fills the higher lines with zero's.
- shiftLeft(n = 1) shifts output channels n pins (default 1) pins left (e.g. leds ). Fills the lower lines with zero's.
- rotateRight(n = 1) rotates output channels to right, moving lowest line to highest line.
- rotateLeft(n = 1) rotates output channels to left, moving highest line to lowest line.
- reverse() revers the "bit pattern" of the lines, high to low and vice versa.
See examples