# 🎸 PCM1808+PCM5102 I2S HAT

65×56mm 2-layer PCB — 1590B Compatible — Rev 1.0

## Top View (Component Side)

## Board Specifications

Dimensions | 65 × 56mm (1590B)
Layers | 2-layer FR4, 1.6mm
Surface Finish | ENIG (gold) preferred
Min Trace | 0.254mm (10mil)
Min Hole | 0.3mm
Mounting | 4× M2.5, 3.2mm holes
Signal Chain
Input | Guitar → J2 (6.35mm TS)
Preamp | U2 TL072 — 20dB gain
ADC | U3 PCM1808 — 24-bit/48kHz I2S
DAC | U4 PCM5102A — 32-bit I2S
Output | → J3 (6.35mm TS) via RC filter
Power
Regulator | U1 AMS1117-3.3 (5V→3.3V)
Decoupling | 100nF + 10µF per IC
Ground | Star ground, GND flood fill
I2S Bus (GPIO)
BCLK | GPIO18 (Pin 12)
LRCLK | GPIO19 (Pin 35)
DIN (to RPi) | GPIO20 (Pin 38) ← PCM1808
DOUT (from RPi) | GPIO21 (Pin 40) → PCM5102
Cost
Board + Components | ~$29.25
+ Enclosure (1590B) | ~$41.75
Qty 5 @ JLCPCB | ~$146.25

⚠️ PCB layout shown is a schematic-derived approximation — the KiCad PCB file (commit 0ae2ca6) has the board outline and mounting holes. Component footprints need human placement review before Gerber export. Open in KiCad to see the actual routed layout.

## Schematic Preview (from KiCad .sch file)

Page 1 — Power
5V rail → U1 AMS1117 → 3.3V
C1 (10µF) + C2 (100nF) input decoupling
C3 (10µF) + C4 (100nF) output decoupling
Page 2 — RPi Header
J1 2×20 stacking header
All 40 GPIO pins pass through
I2S: BCLK(18) LRCLK(19) DIN(20) DOUT(21)
Page 3 — Preamp
J2 Guitar in → R1(1MΩ) pulldown
→ R2(10k) → U2 TL072 non-inv (+) input
Gain = 1 + R3(100k)/R4(10k) = ~20dB
→ C5(10µF) DC-block → PCM1808
Page 4 — ADC + DAC
U3 PCM1808: I2S, 48kHz, always active
C6(100nF) + C7(10µF) decoupling
U4 PCM5102: low-latency filter, unmuted
C8(100nF) + C9(10µF) decoupling
Output → R5(330Ω) + C10(10µF) → J3
Page 5 — Output Buffer
U2 TL072 (half 2): output buffer stage
R6(10k) feedback resistor
I2S Bus Labels
Global net labels: I2S_BCLK, I2S_LRCLK
I2S_DIN (RPi←ADC), I2S_DOUT (RPi→DAC)