XL9535

A Python library for controlling the XL9535 I2C GPIO expander. This library provides an easy-to-use interface for managing relays or GPIOs via the XL9535 chip over I2C, suitable for Raspberry Pi and other Linux-based systems.

Features

• Simple API to control relays or GPIOs via XL9535
• Set and get relay states
• Input validation and error handling
• Designed for extensibility and integration
• Includes unit tests with mocking for I2C

Requirements

• Python 3.7+
• smbus2
• Linux-based system with I2C support (e.g., Raspberry Pi)

Installation

Install the library and its dependencies:

pip install smbus2
# If using as a package:
pip install .

Usage

Basic Example

from src.main import XL9535
import time

# Initialize the XL9535 (default I2C bus 1, address 0x20)
xl9535 = XL9535()

# Turn ON relay 0 on port 0
xl9535.set_relay(port=0, relay_num=0, state=1)

# Check relay state
state = xl9535.get_relay_state(port=0, relay_num=0)
print(f"Relay 0 state: {state}")

# Turn OFF relay 0 on port 0
xl9535.set_relay(port=0, relay_num=0, state=0)

Error Handling

The library raises ValueError for invalid arguments and propagates IOError for I2C communication errors. Use try/except blocks as needed:

try:
    xl9535.set_relay(port=2, relay_num=0, state=1)  # Invalid port
except ValueError as e:
    print(f"Argument error: {e}")

API Reference

XL9535(bus_number: int = 1, address: int = 0x20)

• Initialize the XL9535 device.
• bus_number: I2C bus number (default: 1)
• address: I2C address (default: 0x20)

set_relay(port: int, relay_num: int, state: int) -> None

• Set the state of a relay (0 = OFF, 1 = ON).
• Raises ValueError for invalid arguments, IOError for I2C errors.

get_relay_state(port: int, relay_num: int) -> Optional[int]

• Get the state of a relay (0 = OFF, 1 = ON).
• Returns None if an I2C error occurs.

Running Tests

Unit tests are provided in the tests/ directory. To run tests:

python -m unittest discover tests

Example: Cycling All Relays

from src.main import XL9535
import time

xl9535 = XL9535()

def set_relays(state, start, end, step):
    for relay_num in range(start, end, step):
        for port in [0, 1]:
            xl9535.set_relay(port=port, relay_num=relay_num, state=state)
            time.sleep(0.1)

for _ in range(10):
    set_relays(state=1, start=0, end=8, step=1)   # Turn relays ON
    set_relays(state=0, start=7, end=-1, step=-1) # Turn relays OFF

License

MIT License. See LICENSE.md for details.

Contributing

Contributions are welcome! Please see CONTRIBUTING.md for guidelines.

Code of Conduct

This project adheres to a Code of Conduct. By participating, you are expected to uphold this code.

Contact

For questions or support, contact Aina261 on Github.