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122 lines
4.4 KiB
Markdown
122 lines
4.4 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/PCF8575/blob/master/LICENSE)
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[](https://github.com/RobTillaart/PCF8575/releases)
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# PCF8575
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Arduino library for PCF8575 - 16 channel I2C IO expander
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## Description
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Related to the PCF8574 8 channel IO expander library https://github.com/RobTillaart/PCF8574
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The library gives easy control over the 16 pins of the PCF8575 chips.
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Base address = 0x20 + 0..7 depending on address pins A0..A2
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| TYPE | ADDRESS-RANGE | notes |
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|:---------|:-------------:|:------------------------:|
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|PCF8575 | 0x20 to 0x27 | same range as PCF8574 !! |
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| | | |
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So you can connect up to 8 PCF8575 on one I2C bus, giving access
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to 8 x 16 = 128 IO lines.
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To maximize IO lines combine 8 x PCF8575 + 8 x PCF8574A giving
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128 + 64 = 192 IO lines.
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Be sure to have a well dimensioned power supply.
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The library allows to read and write both single pins or 16 pins at once.
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Furthermore some additional functions are implemented that are
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playful but useful.
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## I2C Clock
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Testing showed that the PCF8575 still works at 600 KHz and failed at 800 KHz.
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These values are outside the specs of the datasheet so they are not recommended.
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However when performance is needed you can try to overclock the chip.
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## Interface
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**PCF8575_INITIAL_VALUE** is a define that can be set compile time or before
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the include of "pcf8575.h" to overrule the default value used with the
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**begin()** call.
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### Constructor
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- **PCF8575(deviceAddress, TwoWire \*wire = &Wire)** Constructor with I2C device address,
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and optional the Wire interface as parameter.
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- **begin(val = PCF8575_INITIAL_VALUE)** set the initial value for the pins and masks.
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- **begin(sda, scl, val = PCF8575_INITIAL_VALUE)** idem, for the ESP32 where one can choose the I2C pins
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What needs to be added in the future is a parameter to choose another Wire interface
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as some processors have multiple hardware Wire interfaces.
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- **isConnected()** checks if the address is visible on the I2C bus
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- **bool setAddress(const uint8_t deviceAddress)** sets the device address after construction.
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Can be used to switch between PCF8575 modules runtime. Note this corrupts internal buffered values,
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so one might need to call **read16()** and/or **write16()**. Returns true if address can be found on I2C bus.
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- **uint8_t getAddress()** returns the device address.
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### Read and Write
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- **read16()** reads all 16 pins at once. This one does the actual reading.
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- **read(pin)** reads a single pin; pin = 0..15
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- **value()** returns the last read inputs again, as this information is buffered
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in the class this is faster than reread the pins.
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- **write16(value)** writes all 16 pins at once. This one does the actual reading.
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- **write(pin, value)** writes a single pin; pin = 0..15; value is HIGH(1) or LOW (0)
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- **valueOut()** returns the last written data.
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### Button
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- **setButtonMask(mask)**
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- **readButton16()**
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- **readButton16(mask)**
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- **readButton(pin)**
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### Special
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- **toggle(pin)** toggles a single pin
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- **toggleMask(mask)** toggles a selection of pins,
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if you want to invert all pins use 0xFFFF (default value)
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- **shiftRight(n = 1)** shifts output channels n pins (default 1) pins right (e.g. leds ).
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Fills the higher lines with zero's.
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- **shiftLeft(n = 1)** shifts output channels n pins (default 1) pins left (e.g. leds ).
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Fills the lower lines with zero's.
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- **rotateRight(n = 1)** rotates output channels to right, moving lowest line to highest line.
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- **rotateLeft(n = 1)** rotates output channels to left, moving highest line to lowest line.
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- **reverse()** revers the "bit pattern" of the lines, high to low and vice versa.
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### Misc
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- **lastError()** returns the last error from the lib. (see .h file)
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## Error codes
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| name | value | description |
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|:-------------------|:-----:|:------------------------|
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| PCF8574_OK | 0x00 | no error |
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| PCF8574_PIN_ERROR | 0x81 | pin number out of range |
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| PCF8574_I2C_ERROR | 0x82 | I2C communication error |
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## Testing
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Testing the initial library is done by Colin Mackay (thanks!).
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Platforms used for testing include: Nano, ESP32 and Seeed Xiao
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## Operation
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See examples
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