Ryan Malloy
b5794c5f8d
- wiring.md: Pin mapping table, module pinout, logic levels - wiring-diagram.svg: Visual connection diagram (S2 Mini ↔ HMC472A) - hmc472-controller.kicad_pro/sch: KiCad project for EDA work GPIO1-6 → V1-V6 (active-low, 16/8/4/2/1/0.5 dB) 5V VBUS → +5V, GND → GND
86 lines
3.2 KiB
Markdown
86 lines
3.2 KiB
Markdown
# HMC472A Attenuator Controller Wiring
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## Connection Diagram
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## Pin Mapping Table
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| ESP32-S2 Mini | HMC472A Module | Function | Attenuation |
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|---------------|----------------|----------|-------------|
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| GPIO1 | V1 | Bit 5 (MSB) | 16 dB |
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| GPIO2 | V2 | Bit 4 | 8 dB |
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| GPIO3 | V3 | Bit 3 | 4 dB |
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| GPIO4 | V4 | Bit 2 | 2 dB |
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| GPIO5 | V5 | Bit 1 | 1 dB |
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| GPIO6 | V6 | Bit 0 (LSB) | 0.5 dB |
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| 5V (VBUS) | +5V | Power | — |
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| GND | GND | Ground | — |
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## HMC472A Module Header Pinout
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The 8-pin header on the HMC472A module (top to bottom when viewing from component side):
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| Pin | Signal | Description |
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|-----|----------|--------------------------|
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| 1 | +5V | Power supply (+5V DC) |
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| 2 | V6 | 0.5 dB control (active-low) |
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| 3 | V5 | 1 dB control (active-low) |
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| 4 | V4 | 2 dB control (active-low) |
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| 5 | V3 | 4 dB control (active-low) |
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| 6 | V2 | 8 dB control (active-low) |
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| 7 | V1 | 16 dB control (active-low) |
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| 8 | GND | Ground |
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## Logic Levels
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**Active-LOW control:**
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- **LOW (0V)** = Attenuate (apply the dB value)
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- **HIGH (3.3V or 5V)** = Pass (0 dB contribution)
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The HMC472A accepts 0–5V TTL/CMOS logic. The ESP32-S2's 3.3V GPIO output is fully compatible.
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## Attenuation Examples
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| GPIO State (1-6) | Step | Total Attenuation |
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|------------------|------|-------------------|
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| `111111` (all HIGH) | 0 | 0 dB (insertion loss only) |
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| `111110` | 1 | 0.5 dB |
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| `111100` | 3 | 1.5 dB |
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| `110000` | 15 | 7.5 dB |
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| `100000` | 31 | 15.5 dB |
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| `000000` (all LOW) | 63 | 31.5 dB |
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Formula: `attenuation = step × 0.5 dB` where step = 0–63
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## ESP32-S2 Mini Physical Pinout
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```
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┌─────────────────┐
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│ USB-C │
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└─────────────────┘
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3V3 ─┤ 1 16 ├─ 5V (VBUS) ◄── Power to HMC472A
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GPIO1 ─┤ 2 15 ├─ GPIO15 (LED)
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GPIO2 ─┤ 3 14 ├─ GPIO14
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GPIO3 ─┤ 4 13 ├─ GPIO13
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GPIO4 ─┤ 5 12 ├─ GPIO12
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GPIO5 ─┤ 6 11 ├─ GPIO11
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GPIO6 ─┤ 7 10 ├─ GPIO10
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GND ─┤ 8 9 ├─ GPIO9
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└─────────────────┘
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(Left header)
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```
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GPIOs 1–6 are on the left header, pins 2–7. Convenient sequential layout for ribbon cable.
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## KiCad Schematic
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A full KiCad schematic is available at `hmc472-controller.kicad_sch` for detailed EDA work.
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## Notes
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1. **No level shifting required** — ESP32-S2 3.3V GPIO drives HMC472A directly
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2. **Boot state** — GPIOs default HIGH at boot = 0 dB attenuation (safe)
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3. **Glitch-free switching** — Firmware uses register-level writes (`GPIO.out_w1ts`/`GPIO.out_w1tc`) to change all 6 bits atomically
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4. **Power** — The S2 Mini's 5V pin sources USB VBUS directly, sufficient for HMC472A's 2.5 mA draw
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