Gamepad Joystick — Magnetic Signal Acquisition

How Hall-effect sensors & magnets translate physical position into digital signals

1. Magnet Activation Map

A magnetic joystick carries a single permanent magnet on the stick tip. As you move the stick, the magnet sweeps past fixed Hall-effect sensors on the PCB. Move your mouse over the joystick to see sensor activation.

Magnet

Active sensor

Weak sensor

Joystick tip

2. Signal Resolution — 5 Second Rolling Window

Move your mouse over the joystick above — the graphs below update in real time, recording the last 5 seconds of movement at three different ADC resolutions.

5-bit (32 steps)

8-bit (256 steps)

12-bit (4096 steps)

Quantisation error is the gap between the real analog value and the nearest digital step.

5-bit: 32 steps, step size ~3.1 %. Notice the "staircase" — large bands. Good for cheap toys.
8-bit: 256 steps, step size ~0.4 %. Smooth enough for most games.
12-bit: 4096 steps, step size ~0.024 %. Near-perfect — only visible on precise measurements.

The dashed line is the raw ADC reading; the solid line is the quantised output. Drag the joystick and watch how the same motion maps to very different digital signals.

3. Signal Quality — Noise & Jitter

Real Hall sensors pick up electromagnetic noise. Higher resolution makes noise more visible in raw ADC readings. The jitter is live — each frame regenerates the noise to show the raw ADC reading.

Why higher bits can be worse without filtering: A 12-bit ADC resolves changes of 5 V / 4096 ≈ 1.2 mV. Tiny EMI, temperature drift, or magnet imperfections become visible as jitter. Cheap 5-bit controllers skip this problem because their coarse quantization (156 mV steps) naturally hides jitter — but at the cost of precision.

4. Quick Reference — Bit Depth Comparison

Property	5-bit	8-bit	12-bit
Steps per axis	32	256	4 096
Quantisation step	~3.125 %	~0.39 %	~0.024 %
Max quantisation error	±1.56 %	±0.20 %	±0.012 %
Typical ADC	8-bit ADC (top 5 bits)	8-bit ADC	12-bit ADC / oversampled
Cost	$	$$	$$$
Best for	Budget / retro toys	Mainstream controllers	Precision / sims
Noise sensitivity	Low (jitter hidden)	Moderate	High (needs filtering)

🕹️ Gamepad Joystick Signal Acquisition

1. Magnet Activation Map

2. Signal Resolution — 5 Second Rolling Window

3. Signal Quality — Noise & Jitter

4. Quick Reference — Bit Depth Comparison