Ryan Malloy a425b4c324 Add OLED display support, standardize Serial0 for UART output

- Add SSD1306 128x64 OLED display with attenuation bar, dB readout,
  step counter, sweep indicator, and WiFi RSSI
- Switch all debug output to Serial0 (UART0 via CH343) for consistent
  serial comms when USB CDC is not used
- Remove unused USB.h includes from all source files
- Add development notes to CLAUDE.md (no stty, serial config docs)

2026-02-08 14:10:44 -07:00

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HMC472 Based RF Attenuator

Overview

6-bit digital RF attenuator module based on the Analog Devices HMC472A GaAs MMIC. 0.5 dB steps, 0–31.5 dB range, DC–3.8 GHz. Single +5V supply, SMA connectors, 50Ω impedance. Manual control via 6-position pin header (active-low TTL/CMOS).

External Links

Local Resources

Datasheet (`datasheet/`)

hmc472a.pdf — Full Analog Devices datasheet (8 pages)
hmc472a.md — Extracted markdown version with all specs, tables, pin descriptions, and application notes
page_001.png through page_008.png — Individual page images
vectors/ — SVG extractions from each datasheet page
- hmc472a_page_N.svg — Full page vector renders (pages 1–8)
- hmc472a_page_N_drawings.svg — Isolated drawings/diagrams only (pages 1–8)

Module Documentation (`docs/`)

module-specs.md — Consolidated module specs: electrical specs, truth table, pin assignments, application circuit, performance graphs
electrical-specifications.jpg — Electrical specs table from datasheet
bias-voltage-current-control-voltage-truth-table.jpg — Bias/control voltage and truth table
functional-diagram-application-circuit.jpg — Block diagram and recommended application circuit
insertion-and-return-loss-graphs.jpg — Performance graphs across frequency/temperature

Product Photos (`marketing/`)

Front and back board photos showing HMC472A IC, SMA connectors, 6-pin header, and passive components

Key Specs (Quick Reference)

Parameter	Value
Frequency Range	DC – 3.8 GHz
Attenuation	0 – 31.5 dB (0.5 dB steps)
Insertion Loss	1.4 – 1.9 dB typ
Step Error	± 0.25 dB typ
IIP3	+49 to +54 dBm
Supply	+5V, 2.5 mA typ
Max Input Power	+20 dBm (module) / +28 dBm (IC abs max)
Switching	40–60 ns
Control	6 pins, active-low (Low = attenuate)

Truth Table (Control Pins)

Pin	Attenuation (when Low)
V1	16 dB
V2	8 dB
V3	4 dB
V4	2 dB
V5	1 dB
V6	0.5 dB

All High = reference (insertion loss only). All Low = 31.5 dB. Any combination sums.

Development Notes

Serial Port Access

NEVER use stty commands — they corrupt terminal settings and break Claude Code's UI/history. Use these instead:

mcserial MCP (preferred) — mcp__mcserial__* tools for all serial operations
Python — pyserial for scripted serial work

ESP32-S3 Serial Configuration

The ESP32-S3-DevKitC-1 has two serial interfaces:

Serial0 (UART0) — Hardware UART via CH343 bridge (GPIO43/44) → /dev/ttyACM*
Serial (USB CDC) — Native USB OTG port → requires USB.begin()

This project uses Serial0 for all debug output since we connect via the CH343 UART bridge.

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