GY-63_MS5611/libraries/PCF8575

PCF8575

Arduino library for PCF8575 - 16 channel I2C IO expander

Description

Related to the PCF8574 8 channel IO expander library https://github.com/RobTillaart/PCF8574

The library gives easy control over the 16 pins of the PCF8575 chips.

Base address = 0x20 + 0..7 depending on address pins A0..A2

TYPE	ADDRESS-RANGE	notes
PCF8575	0x20 to 0x27	same range as PCF8574 !!

So you can connect up to 8 PCF8575 on one I2C bus, giving access to 8 x 16 = 128 IO lines. To maximize IO lines combine 8 x PCF8575 + 8 x PCF8574A giving 128 + 64 = 192 IO lines. Be sure to have a well dimensioned power supply.

The library allows to read and write both single pins or 16 pins at once. Furthermore some additional functions are implemented that are playful but useful.

I2C Clock

Testing showed that the PCF8575 still works at 600 KHz and failed at 800 KHz. These values are outside the specs of the datasheet so they are not recommended. However when performance is needed you can try to overclock the chip.

Interface

PCF8575_INITIAL_VALUE is a define that can be set compile time or before the include of "pcf8575.h" to overrule the default value used with the begin() call.

Constructor

• PCF8575(deviceAddress, TwoWire *wire = &Wire) Constructor with I2C device address, and optional the Wire interface as parameter.
• begin(val = PCF8575_INITIAL_VALUE) set the initial value for the pins and masks.
• begin(sda, scl, val = PCF8575_INITIAL_VALUE) 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.
• isConnected() checks if the address is visible on the I2C bus
• bool setAddress(const uint8_t deviceAddress) sets the device address after construction. Can be used to switch between PCF8575 modules runtime. Note this corrupts internal buffered values, so one might need to call read16() and/or write16(). Returns true if address can be found on I2C bus.
• uint8_t getAddress() returns the device address.

Read and Write

• read16() reads all 16 pins at once. This one does the actual reading.
• read(pin) reads a single pin; pin = 0..15
• value() returns the last read inputs again, as this information is buffered in the class this is faster than reread the pins.
• write16(value) writes all 16 pins at once. This one does the actual reading.
• write(pin, value) writes a single pin; pin = 0..15; value is HIGH(1) or LOW (0)
• valueOut() returns the last written data.

Button

• setButtonMask(mask)
• readButton16()
• readButton16(mask)
• readButton(pin)

Special

• toggle(pin) toggles a single pin
• toggleMask(mask) toggles a selection of pins, if you want to invert all pins use 0xFFFF (default value)
• 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.

Misc

• lastError() returns the last error from the lib. (see .h file)

Error codes

name	value	description
PCF8574_OK	0x00	no error
PCF8574_PIN_ERROR	0x81	pin number out of range
PCF8574_I2C_ERROR	0x82	I2C communication error

Testing

Testing the initial library is done by Colin Mackay (thanks!). Platforms used for testing include: Nano, ESP32 and Seeed Xiao

Operation

See examples