Adafruit 4120 CharliePlex

The Adafruit 4120 is a 16×8 CharliePlex LED matrix bonnet driven by the IS31FL3731 controller. It communicates over I2C and produces a monochrome green display suitable for compact status readouts and scrolling text.

CyberHUD provides a single panel definition for this board.

Quick Start

CLIJSON config

sudo ./cyberhudd -panel adafruit-4120-charlieplex

In your /etc/cyberhudd.json:

{
  "display": {
    "panel": "adafruit-4120-charlieplex"
  }
}

Display Characteristics

Property	Value
Resolution	16 × 8 pixels
Color format	Monochrome (green LED)
Controller	IS31FL3731
Interface	I2C
Input	None

Troubleshooting

CyberHUD emits detailed diagnostic logs during panel initialization. Check them with:

sudo journalctl -u cyberhudd.service -n 50

Common Issues

Symptom	Likely Cause	Fix
i2c device ... open=error	I2C not enabled on the Raspberry Pi	Run sudo raspi-config → Interface Options → I2C → Enable, then reboot
Display shows no LEDs lit	Wrong I2C address or bus	Verify the bonnet is seated correctly; run i2cdetect -y 1 to confirm address 0x74 appears
Only partial rows illuminate	Incorrect panel name or orientation mismatch	Check panel name spelling; ensure no other I2C device conflicts on the bus

Related Pages

• Hardware Identification — find your panel name
• Pin Assignments — custom pin overrides