Pi4J :: Java I/O Library for Raspberry Pi :: Devices

Collection of devices implemented for use with Pi4J V2.

Project by Tom Aarts.

Note: This repository has a tag identifying the code level that works with
2.4.0-SNAPSHOT.   Commits newer than this tag are migrations to the 
2.6.0-SNAPSHOT. These commits may contain  code using providers and/or Pi4J-V2
interfaces not available in prior SNAPSHOTs.. 

The following lists the currently supported devices within this project:

• 1602A LCD HD44780U: App uses SN74HC595 to control the LCD
• 1602A LCD MCP23017 I2C Controller: App uses MCP23017 to control the LCD
• 1602A_LCD_PCF8574A I2C Controller: App uses PCF8574A to control the LCD
• ADS1256 24bit A-to-D (1)
• AT24C512 SEEPROM (1) (2)
• BMP280 Temperature and Pressure Sensor (1)
• BME280 Temperature, Pressure and Humidity Sensor (I2C & SPI) (1)(3)
• DAC8552 16bit DAC SPI connected (3)
• DHT22 Temp/Humidity sensor (1)
• HC-SR04 Ultrasonic Sensor
• Is31fl3731 matrix controller (1)
• MCP23008 drive and read chip GPIOs
• MCP23008 and MCP23017 Pin monitoring (interrupt support)
• MCP23017 drive and read chip GPIOs
• MCP3008 A/D 10bit converter (1)(3)
• MCP4725 12 bit DAC (1)
• MPL3115A2 Temp/Pressure/Altitude device (1)
• NeoPixel94V Intelligent Control LED device (1)(3)
• QT Rotary Encoder (1)
• SN74HC595 8 Bit shift register (1)
• SSD1306 OLED I2C (1)
• TCA9548 (1x8 I2C switch)
• VL53L0X TimeOfFlight device (1)

Notes:

(1): This package uses code within this repo and Pi4J \ (2): Requires 2.2.2-SNAPSHOT of Pi4j that supports i2c multibyte write/restart \ (3): SPI versions of the device uses Pigpio, cannot be used on Raspberry Pi5 \

GPIO monitor

This repository includes two Python scripts to monitor GPIO pin states in real-time on a Raspberry Pi. \ Note: These scripts use the pigpio library, which is currently incompatible with the Raspberry Pi 5.

Setting Up pigpio

To install pigpio, run:

pip install pigpio

Also, make sure the pigpiod daemon is running before executing either script:

sudo pigpiod

1. monitor.py

This script provides a detailed, line-by-line log of GPIO state changes, including the time difference in microseconds between state changes for each pin.

• Usage:

python3 monitor.py              # Monitor all GPIO pins
python3 monitor.py 23 24 25     # Monitor only GPIO pins 23, 24, and 25

• Features:
  • Logs state changes (HIGH/LOW) for each monitored GPIO pin.
  • Displays the time difference between successive state changes in microseconds.
  • Structured with modular functions for initializing GPIO monitoring, handling state changes, and cleanup on exit.
• Example Output:

Monitoring GPIO pins... Press Ctrl+C to stop.
GPIO=23 Level=1 Time Diff=120 μs
GPIO=24 Level=0 Time Diff=95 μs
GPIO=25 Level=1 Time Diff=110 μs

2. monitor_table_format.py

This script offers a compact, tabular format for monitoring GPIO states, displaying the current state of each pin in a single, updating line. This view is ideal for visualizing slow state changes without excessive log clutter.

• Usage:

  python3 monitor_table_format.py          # Monitor all GPIO pins
  python3 monitor_table_format.py 23 24 25 # Monitor only GPIO pins 23, 24, and 25

• Features:

  • Displays pin states in a single, continuously updating line.
  • Ideal for slow changes, as it reduces visual clutter by showing only the current state of each pin.
  • Automatically updates the state every second (customizable by adjusting the sleep interval).

• Example Output:

Monitoring GPIO pins... Press Ctrl+C to stop.
GPIO   23 | 24 | 25
STATE   1 |  0 |  1