feat: PCM1808+PCM5102 I2S HAT design files

Custom I2S HAT for Pi Multi-FX Pedal — full hardware package: - KiCad project: schematic (kicad_sch), PCB layout (kicad_pcb), project file - Custom DT overlay: pcm1808-pcm5102-overlay.dts (no upstream overlay exists for PCM1808) - docs/hardware-bom.md: BOM (9.25 HAT + 1.75 with enclosure), wiring diagram, PCB design notes - docs/config-audio.md: DT overlay build, ALSA config, JACK integration, troubleshooting - scripts/install_hat.sh: One-command install + test suite (6 tests) - hardware/gerber/: JLCPCB fab instructions and assembly notes Circuit: Guitar input → TL072 preamp (gain ~20dB) → PCM1808 ADC → RPi I2S → PCM5102 DAC → RC filter → output jack I2S: BCLK/GPIO18, LRCLK/GPIO19, DIN/GPIO20, DOUT/GPIO21 Stacking header passes all 40 GPIO pins for footswitches/LEDs/display
2026-06-07 23:52:13 -04:00
parent 0e77adb4c3
commit 0ae2ca6e8e
8 changed files with 1269 additions and 0 deletions
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+// SPDX-License-Identifier: GPL-2.0
+// Device Tree Overlay for PCM1808 ADC + PCM5102 DAC I2S combo
+// Pi Multi-FX Pedal — Ourpad Networks
+//
+// PCM1808: 24-bit stereo ADC (we use single-channel mono guitar input)
+//   - I2S slave mode (BCLK + LRCK from RPi)
+//   - FMT = GND (I2S, 24-bit left-justified)
+//   - MD1 = 3.3V (48kHz sampling rate)
+//   - MD0 = GND (standby disabled, always active)
+//
+// PCM5102: 32-bit stereo DAC
+//   - I2S slave mode (BCLK + LRCK from RPi)
+//   - FLT = GND (normal operation, low-latency filter)
+//   - DEMP = GND (no de-emphasis)
+//   - XSMT = 3.3V (unmuted, always active)
+//
+// Wiring:
+//   GPIO18 (BCLK)  → PCM1808 pin 8 (BCK)  → PCM5102 pin 14 (BCK)
+//   GPIO19 (LRCLK) → PCM1808 pin 7 (LRCK) → PCM5102 pin 13 (LRCK)
+//   GPIO20 (DIN)   ──────────────────────────→ PCM5102 pin 12 (DIN)
+//   GPIO21 (DOUT)  → PCM1808 pin 9 (DOUT)
+//   3.3V           → PCM1808 VCC           → PCM5102 Vin
+//   GND            → PCM1808 GND           → PCM5102 GND
+
+/dts-v1/;
+/plugin/;
+
+/ {
+    compatible = "brcm,bcm2711";  // RPi 4B
+
+    fragment@0 {
+        target = <&i2s>;
+        __overlay__ {
+            status = "okay";
+            #sound-dai-cells = <0>;
+        };
+    };
+
+    // PCM1808 ADC — captured via I2S DOUT (GPIO21)
+    fragment@1 {
+        target = <&i2s>;
+        __overlay__ {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            pcm1808: pcm1808@0 {
+                compatible = "ti,pcm1808";
+                reg = <0>;              // I2S device 0 (first codec on bus)
+                status = "okay";
+                #sound-dai-cells = <0>;
+            };
+        };
+    };
+
+    // PCM5102 DAC — driven via I2S DIN (GPIO20)
+    fragment@2 {
+        target = <&i2s>;
+        __overlay__ {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            pcm5102: pcm5102@1 {
+                compatible = "ti,pcm5102a";
+                reg = <1>;              // I2S device 1 (second codec on bus)
+                status = "okay";
+                #sound-dai-cells = <0>;
+            };
+        };
+    };
+
+    // Simple audio card binding ADC + DAC
+    fragment@3 {
+        target = <&sound>;
+        __overlay__ {
+            compatible = "simple-audio-card";
+            status = "okay";
+
+            simple-audio-card,name = "pcm1808-pcm5102-hat";
+
+            // RPi is I2S master
+            simple-audio-card,format = "i2s";
+            simple-audio-card,bitclock-master = <&cpu_dai>;
+            simple-audio-card,frame-master = <&cpu_dai>;
+
+            // 48kHz / 24-bit
+            simple-audio-card,mclk-fs = <256>;  // 48kHz * 256 = 12.288MHz
+
+            cpu_dai: simple-audio-card,cpu {
+                sound-dai = <&i2s>;
+            };
+
+            // PCM1808 ADC — capture path
+            pcm1808_dai: simple-audio-card,codec@0 {
+                sound-dai = <&pcm1808>;
+                format = "i2s";
+                bitclock-master;
+                frame-master;
+            };
+
+            // PCM5102 DAC — playback path
+            pcm5102_dai: simple-audio-card,codec@1 {
+                sound-dai = <&pcm5102>;
+                format = "i2s";
+                bitclock-master;
+                frame-master;
+            };
+        };
+    };
+
+    __overrides__ {
+        bclk-pin = <&i2s>,"bcm,pin-functions:18";
+        lrclk-pin = <&i2s>,"bcm,pin-functions:19";
+        din-pin   = <&i2s>,"bcm,pin-functions:20";
+        dout-pin  = <&i2s>,"bcm,pin-functions:21";
+    };
+};