micheleandCursor
fcda4ef151
Add wrapping table columns, breakable paths, and ragged callout boxes in digiradio-manual.sty, then reflow long endpoint headings, JSON examples, and hardware/driver tables to stay within page margins. Co-authored-by: Cursor <cursoragent@cursor.com>
502 lines
20 KiB
TeX
502 lines
20 KiB
TeX
\chapter{Hardware Overview}
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\label{ch:hardware}
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This chapter describes the board in detail: the design choices behind it,
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each integrated circuit and how it is controlled, the bus architecture,
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and the inter-chip connections. The complete hardware design ---
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schematics, PCB, Gerbers, and bill of materials --- is published in the
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repository under the CERN-OHL-S v2 licence.
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\section{Design philosophy}
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\label{sec:hw-philosophy}
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Every major choice on the board serves audio quality and
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reproducibility.
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\begin{drkey}[The four-chip split]
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Rather than a single all-in-one radio IC, DigiRadio separates concerns:
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a dedicated tuner for reception, a dedicated DSP for audio conditioning,
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a dedicated Bluetooth module for the wireless codec, and a general-purpose
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host to coordinate them. Each stage can be understood, measured, and
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improved on its own.
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\end{drkey}
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The consequences of that split run through the rest of the board: a
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control host that speaks several buses, a clean power tree that keeps the
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tuner's analogue supplies away from digital noise, and careful RF layout
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so the two 2.4\,GHz radios do not interfere.
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\section{System block diagram}
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\label{sec:hw-block}
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Four devices are coordinated by the ESP32-S3. The tuner produces the
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audio stream, the DSP conditions and mixes it, and the Bluetooth module
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transmits it; the host manages all three and provides the network
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interface.
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}L{2.6cm}L{4.2cm}L{2.6cm}L{3.8cm}@{}}
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\drhead Device & Role & Control bus & Firmware \\
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\midrule
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Si4684 & DAB+/FM tuner & SPI & host-loaded image \\
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ADAU1701 & Audio DSP (EQ + mixer) & I\textsuperscript{2}C & host-loaded RAM \\
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ESP32-S3-WROOM-1 & Host, Wi-Fi/BLE & --- & application FW \\
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FSC-BT1035 & Bluetooth 5.2 (aptX Ad.) & UART (AT) & vendor FW + config \\
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\bottomrule
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\end{tabular}
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\caption{Principal integrated circuits, their control bus, and how each
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receives its firmware or configuration.}
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\label{tab:hw-ics}
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\end{table}
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\section{The tuner: Si4684}
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\label{sec:hw-si4684}
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The Si4684 is a single-chip DAB+/FM receiver front-end. It delivers the
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decoded audio stream to the DSP and reports signal-quality metrics to the
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host.
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\subsection{Control interface}
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The device is controlled through a command/response protocol over its
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host bus. The host issues a command, then polls a clear-to-send (CTS)
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status bit before reading the response; the driver validates that status
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byte before trusting any returned payload.
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\begin{drkey}[SPI for the tuner]
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The tuner needs a large firmware image loaded at every power-up
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(Section~\ref{sec:hw-si4684-fw}). SPI offers substantially higher
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throughput than I\textsuperscript{2}C, so on DigiRadio the tuner uses
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\textbf{SPI}, keeping boot time short, while the low-rate DSP control uses
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a separate I\textsuperscript{2}C bus.
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\end{drkey}
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\subsection{Firmware image upload}
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\label{sec:hw-si4684-fw}
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The Si4684 holds no application firmware of its own at reset. At power-up
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the host loads a bootloader/patch and then the firmware image for the
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desired mode (FM or DAB). These images are large, so the driver streams
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them to the chip in bounded chunks read from the ESP32's flash, rather
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than buffering a whole image in RAM.
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\begin{drref}[Datasheet]
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The exact power-up, patch, image-load, and boot command sequence follows
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the Si468x programming guide (AN649). No command byte is issued without a
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documented source, and each step in the driver cites its section.
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\end{drref}
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\section{The audio DSP: ADAU1701}
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\label{sec:hw-adau}
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The ADAU1701 is a SigmaDSP audio processor. In DigiRadio it performs
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equalisation and mixes the tuner audio with the ESP32 audio source before
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the signal reaches the Bluetooth stage.
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\subsection{Control and program loading}
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The DSP is controlled over I\textsuperscript{2}C. Its signal-processing
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program is designed in SigmaStudio and exported as a sequence of register
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writes (control settings, program RAM, and parameter RAM). The full
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SigmaStudio schematic, signal chain, and runtime parameter map are
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documented in Chapter~\ref{ch:sigmastudio}. Driver boot, safeload API,
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\texttt{AudioService}, and HTTP integration are in
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Chapter~\ref{ch:adau1701}.
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\begin{drkey}[RAM boot, no EEPROM]
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The board deliberately omits the ADAU1701 self-boot EEPROM. Instead, the
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ESP32 writes the exported program into the DSP's RAM at \emph{every} boot.
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This keeps the audio processing under host control and field-updatable ---
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a new EQ or mixer configuration is a firmware update, not a chip
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re-programming.
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\end{drkey}
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\subsection{Click-free parameter updates}
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Runtime changes --- adjusting an EQ band, changing a mix level --- are
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applied through the ADAU1701 safeload mechanism, which updates parameter
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cells atomically between audio samples. Writing parameter cells directly
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while audio plays would produce audible clicks and is not done.
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\section{The Bluetooth module: FSC-BT1035}
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\label{sec:hw-bt1035}
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The FSC-BT1035 (Qualcomm QCC3056) is a Bluetooth~5.2 audio transmitter
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with aptX, aptX~HD, and aptX~Adaptive support --- the high-resolution
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codecs that make the wireless output hi-fi rather than merely convenient.
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\subsection{Control interface}
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The module is controlled with AT commands over UART, with hardware flow
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control (RTS/CTS). The host sends commands and parses the module's
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responses explicitly, treating timeouts as errors. Some settings are held
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in the module's own non-volatile memory.
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\begin{drcaution}[I\textsuperscript{2}S slave mode]
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The PCB routes ADAU1701 \texttt{SDATA\_OUT0} to the module over
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I\textsuperscript{2}S (BCLK, LRCLK, PCM data). Firmware must initialise
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\texttt{AT+AUXCFG=3} and \texttt{AT+I2SCFG=67}, not Line-In
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(\texttt{AT+AUXCFG=1}). See Chapter~\ref{ch:bt1035}, Section~\ref{sec:bt1035-i2s}.
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\end{drcaution}
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\section{The host: ESP32-S3}
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\label{sec:hw-esp32}
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The ESP32-S3-WROOM-1 coordinates the whole system. It loads the tuner and
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DSP firmware at boot, controls all three companion chips over their
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respective buses, serves the configuration web interface, and provides
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Wi-Fi connectivity. Its dual-core processor and generous RAM comfortably
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handle the firmware images and the network stack alongside the control
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tasks.
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\section{Bus architecture}
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\label{sec:hw-buses}
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The host speaks several interfaces, each chosen for its traffic:
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
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\drhead Bus & Devices & Purpose \\
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\midrule
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SPI & Si4684 & fast firmware-image upload, tuner control \\
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I\textsuperscript{2}C & ADAU1701, 24AA025E48 EEPROM & DSP control, device identity \\
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UART & FSC-BT1035 & AT command / response (with RTS/CTS) \\
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I\textsuperscript{2}S & Si4684, ESP32, ADAU1701, BT1035 & audio (ADAU is master) \\
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\bottomrule
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\end{tabular}
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\caption{Interface assignment and rationale.}
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\label{tab:hw-buses}
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\end{table}
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\section{Power}
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\label{sec:hw-power}
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The board is powered from USB-C. An AP63203 buck converter generates the
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main rail from the USB input, feeding the digital and analogue sections.
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The tuner's sensitive supplies are derived and filtered separately to keep
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RF performance clean.
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\section{RF and antennas}
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\label{sec:hw-rf}
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Two 2.4\,GHz radios are present --- the ESP32-S3 and the Bluetooth module.
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Their antennas are placed on opposite diagonal corners of the board to
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maximise separation and minimise mutual desense. Each module keeps its
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antenna keep-out clear of copper on all layers. The PCB is a six-layer
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stack-up with controlled impedance on the USB and RF sections.
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\section{Inter-chip connections (GPIO map)}
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\label{sec:hw-gpio}
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This section is the authoritative wiring reference between the ESP32-S3
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and the companion chips. The firmware pin definitions
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(\texttt{board\_pins.hpp}) must match these tables exactly.
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\subsection{System and control lines}
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
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\drhead Signal & ESP32-S3 GPIO & Notes \\
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\midrule
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USB D$-$ & GPIO19 & native USB \\
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USB D$+$ & GPIO20 & native USB \\
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Reset / boot button & GPIO0 & strapping pin \\
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\bottomrule
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\end{tabular}
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\caption{System and control lines.}
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\label{tab:hw-sys}
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\end{table}
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\subsection{Si4684 tuner (SPI)}
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}L{2.4cm}L{2.2cm}L{2.8cm}L{5.8cm}@{}}
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\drhead Signal & Si4684 pin & ESP32-S3 GPIO & Notes \\
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\midrule
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SCLK & pin 30 & GPIO13 & \\
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MOSI & pin 31 & GPIO12 & \\
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MISO & pin 32 & GPIO9 & \\
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SSB (CS) & pin 29 & GPIO8 & chip select, active-low \\
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RSTB\# & pin 4 & GPIO38 & active-low, ext.\ pull-down \\
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INTB\# & pin 3 & GPIO39 & active-low, ext.\ pull-up \\
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\bottomrule
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\end{tabular}
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\caption{Si4684 control and SPI lines.}
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\label{tab:hw-si4684}
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\end{table}
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\subsection{ADAU1701 DSP (I\textsuperscript{2}C)}
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
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\drhead Signal & ADAU1701 pin & ESP32-S3 GPIO \\
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\midrule
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SDA & --- & GPIO4 \\
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SCL & --- & GPIO5 \\
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RESET\# & pin 5 & GPIO47 (active-low, ext.\ pull-up) \\
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\bottomrule
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\end{tabular}
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\caption{ADAU1701 control (I\textsuperscript{2}C) and reset. The 7-bit
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I\textsuperscript{2}C address is 0x34 (ADDR0 and ADDR1 tied to GND).}
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\label{tab:hw-adau}
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\end{table}
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\subsection{Device-identity EEPROM (24AA025E48)}
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A 24AA025E48 EEPROM shares the DSP's I\textsuperscript{2}C bus. Besides a
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small general-purpose memory, it carries a factory-programmed, globally
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unique EUI-48 identifier, which the firmware can read to give each unit a
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stable identity --- for example a unique Bluetooth name or a device
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serial number. Its 7-bit address is 0x52 (A0 to GND, A1 to 3V3).
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
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\drhead Device & 7-bit address & Set by \\
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\midrule
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ADAU1701 & 0x34 & ADDR0, ADDR1 = GND \\
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24AA025E48 EEPROM & 0x52 & A0 = GND, A1 = 3V3 (no A2 pin) \\
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\bottomrule
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\end{tabular}
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\caption{I\textsuperscript{2}C address map (shared bus).}
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\label{tab:hw-i2c-addr}
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\end{table}
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\subsection{FSC-BT1035 Bluetooth}
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}L{2.2cm}L{2.2cm}L{2.8cm}L{5.8cm}@{}}
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\drhead Signal & BT1035 pin & ESP32-S3 GPIO & Direction \\
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\midrule
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SYS\_CTL & pin 34 & GPIO15 & ESP32 $\rightarrow$ BT \\
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BT\_CTS & pin 15 & GPIO21 & flow control \\
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BT\_RTS & pin 16 & GPIO14 & flow control \\
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BT\_RX & pin 14 & GPIO40 & ESP32 TX $\rightarrow$ BT RX \\
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BT\_TX & pin 13 & GPIO41 & BT TX $\rightarrow$ ESP32 RX \\
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RESET & pin 8 & GPIO17 & ESP32 $\rightarrow$ BT \\
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\bottomrule
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\end{tabular}
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\caption{FSC-BT1035 UART, control, and reset lines.}
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\label{tab:hw-bt1035}
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\end{table}
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\subsection{Audio bus (I\textsuperscript{2}S)}
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The audio path is a chip-to-chip I\textsuperscript{2}S bus with the
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ADAU1701 acting as master. Table~\ref{tab:hw-i2s} lists the chip-to-chip
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routing; Table~\ref{tab:hw-i2s-esp} lists the ESP32's own
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I\textsuperscript{2}S source lines that feed the mixer.
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
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\drhead Signal & Path & ADAU1701 / BT1035 pins \\
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\midrule
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SDATA\_IN0 & Si4684 $\rightarrow$ ADAU & MP0 (pin 11) \\
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SDATA\_IN1 & ESP32 $\rightarrow$ ADAU & MP1 (pin 10) \\
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SDATA\_OUT0 & ADAU $\rightarrow$ BT1035 & MP6 (pin 15) $\rightarrow$ pin 5 \\
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LRCLK & ADAU $\rightarrow$ BT1035 & MP4 (pin 8) + MP10 (pin 16) $\rightarrow$ pin 7 \\
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BCLK & ADAU $\rightarrow$ BT1035 & MP5 (pin 9) + MP11 (pin 19) $\rightarrow$ pin 4 \\
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\bottomrule
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\end{tabular}
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\caption{I\textsuperscript{2}S audio routing (chip-to-chip). The
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MP4/MP10 and MP5/MP11 pairs are electrically connected on the board.}
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\label{tab:hw-i2s}
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\end{table}
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
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\drhead Signal & ESP32-S3 GPIO & Direction \\
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\midrule
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BCLK & GPIO6 & in from ADAU (master) \\
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LRCLK & GPIO7 & in from ADAU (master) \\
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SDATA\_IN1 & GPIO16 & out $\rightarrow$ ADAU MP1 \\
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\bottomrule
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\end{tabular}
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\caption{ESP32 I\textsuperscript{2}S source lines feeding the mixer. The
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ESP32 is an I\textsuperscript{2}S slave (clocks in), transmitting
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audio data. SDATA\_IN1 lands on ADAU MP1 (pin 10); GPIO16 is the
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ESP32 module's physical pin 9.}
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\label{tab:hw-i2s-esp}
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\end{table}
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\subsection{Completeness}
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\label{sec:hw-gpio-open}
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\begin{drnote}[Map complete]
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The GPIO and I\textsuperscript{2}C maps are complete and match
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\texttt{board\_pins.hpp}. No values remain open.
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\end{drnote}
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This section is the authoritative wiring reference for firmware bring-up:
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the pin definitions in the source code must match it exactly.
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\section{Design validation and critical checks}
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\label{sec:hw-validation}
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This section records the design-review checks performed against the
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component datasheets before fabrication, chip by chip. Items marked
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\emph{critical} can cause permanent damage or a non-functional board if
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violated, and were verified explicitly.
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\subsection{Si4684 tuner}
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\label{sec:hw-val-si4684}
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\begin{drcaution}[Critical --- RSTB and power sequencing]
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The Si4684 datasheet requires that RSTB be held low during any power-supply
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transition and remain asserted for 10\,\textmu s after all supplies are
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stable; failing to do so \emph{may permanently damage the device}. On
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DigiRadio, RSTB (GPIO38) has an external pull-down, so the chip powers up
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held in reset until the ESP32 releases it. \textbf{Verified.} The firmware
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must not drive RSTB high before the Si4684 supplies are stable.
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\end{drcaution}
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\begin{drnote}[Firmware bring-up]
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RSTB is driven only in \texttt{Si4684Driver::boot()}
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(Chapter~\ref{ch:si4684}): GPIO38 is configured as output with
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\texttt{GPIO\_PULLDOWN\_ENABLE} so the net cannot glitch high while the pin
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mode changes, then held low for 5\,ms and released. The internal pull-down
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is \emph{not} redundant with the external resistor: the external pull-down
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holds RSTB during board power-on before \texttt{app\_main}; the internal one
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closes the brief window between \texttt{gpio\_config} and
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\texttt{gpio\_set\_level(0)} where an output register default could otherwise
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violate the datasheet sequencing rule. No other code touches GPIO38. Release
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occurs only after all Si4684 supplies (VA, VIO, VCORE, VMEM) are stable,
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satisfying the +10\,\textmu s requirement in practice.
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\end{drnote}
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}L{3.2cm}L{8.2cm}L{2.2cm}@{}}
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\drhead Check & Requirement (datasheet) & Status \\
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\midrule
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RSTB low at power-up & held low until supplies stable +10\,\textmu s & verified (pull-down) \\
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RSTB release (firmware) & not before supplies stable; boot pulse only & verified (driver) \\
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RSTB glitch guard (firmware) &
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\texttt{GPIO\_PULLDOWN\_ENABLE} in \texttt{gpio\_config} & verified \\
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Core supplies at 1.8\,V & VA = VCORE = VMEM = 1.8\,V & verified \\
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VIO level & 1.62--3.6\,V (3.3\,V to talk to ESP32) & verified \\
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Bypass caps & 2.2\,nF + 1\,\textmu F per VIO/VMEM/VCORE rail & verified \\
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SPI mode & Mode 0 or 3, up to 10\,MHz, SMODE = GND & verified \\
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SSB framing (firmware) & SSB held low for the whole transaction & driver rule \\
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INTB & interrupt line, external pull-up (GPIO39) & verified \\
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\bottomrule
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\end{tabular}
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\caption{Si4684 design checks (datasheet references below).}
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\label{tab:hw-val-si4684}
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\end{table}
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\begin{drref}[Datasheet]
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Power sequencing and SPI framing: \drpath{Hardware/DATASHEET/SI4684-A10.pdf}.
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The user must not pulse SSB high between bytes; SSB frames the whole
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command/reply. Bypass-capacitor values and placement:
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\drpath{Hardware/DATASHEET/AN851.pdf}, \emph{Si468x Schematic and Layout
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Guide}. Boot and command protocol: AN649. Local copies:
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\drpath{Hardware/DATASHEET/} (see \drpath{README.md}).
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\end{drref}
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The core, memory, and analogue rails run at 1.8\,V; only VIO is at 3.3\,V
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to interface the ESP32. The 2.2\,nF and 1\,\textmu F bypass pairs are
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placed close to VIO (pin~34), VMEM (pin~35), and VCORE (pin~37) as AN851
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requires. The VHF antenna input follows the AN851 layout guidance (short,
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narrow microstrip; ground-fill relief; ferrite beads near the connector).
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\subsection{ADAU1701 DSP}
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\label{sec:hw-val-adau}
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\begin{drkey}[Master-clock loopback is mandatory, not optional]
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For an ADAU1701 operating as I\textsuperscript{2}S master while receiving
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data on its serial inputs, the datasheet requires OUTPUT\_LRCLK (MP10) and
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OUTPUT\_BCLK (MP11) to be set to master mode and \emph{connected externally}
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to INPUT\_LRCLK (MP4) and INPUT\_BCLK (MP5). DigiRadio wires exactly this
|
|
loopback (MP10$\rightarrow$MP4, MP11$\rightarrow$MP5). Without it the DSP
|
|
locks up when input data arrives.
|
|
\end{drkey}
|
|
|
|
\begin{table}[htbp]
|
|
\centering
|
|
\small
|
|
\begin{tabular}{@{}L{2.2cm}L{3.6cm}L{7.2cm}@{}}
|
|
\drhead Check & Requirement (datasheet) & Status \\
|
|
\midrule
|
|
Clock loopback & MP10$\rightarrow$MP4, MP11$\rightarrow$MP5 wired & verified \\
|
|
Output master & serial output port in Master Mode & verified \\
|
|
MCLK ratio & exactly 256\,$\times$\,f\textsubscript{S} & verified \\
|
|
MCLK value & 12.288\,MHz oscillator (256\,$\times$\,48\,kHz) & verified \\
|
|
I\textsuperscript{2}C pull-ups & 2\,k\(\Omega\) on SDA/SCL (R16/R1) & verified \\
|
|
I\textsuperscript{2}C address & 0x34 (ADDR0 = ADDR1 = GND) & verified \\
|
|
Self-boot & disabled (host RAM load) & verified \\
|
|
\bottomrule
|
|
\end{tabular}
|
|
\caption{ADAU1701 design checks. Reference: ADAU1701 data sheet (Rev.~C),
|
|
serial-port master/slave section and I\textsuperscript{2}C port.}
|
|
\label{tab:hw-val-adau}
|
|
\end{table}
|
|
|
|
\begin{drref}[Datasheet]
|
|
Master-clock loopback and serial-port modes:
|
|
\texttt{Hardware/DATASHEET/adau1701.pdf}, Rev.~C, Table~63 and the serial-port
|
|
section. The master clock must be exactly 256\,$\times$\,f\textsubscript{S}.
|
|
I\textsuperscript{2}C lines require pull-up resistors on SDA and SCL.
|
|
DigiRadio uses \textbf{2\,k\(\Omega\)} (schematic R1/R16; ADAU1701 datasheet
|
|
recommends 2.2\,k\(\Omega\) --- acceptable at 3.3\,V).
|
|
\end{drref}
|
|
|
|
\begin{drnote}[I\textsuperscript{2}C pull-ups confirmed]
|
|
Schematic \texttt{DigitalRadio.pdf} and BOM list R1 (SCL) and R16 (SDA) as
|
|
2\,k\(\Omega\) to 3V3 on the shared ADAU1701/EEPROM bus.
|
|
\end{drnote}
|
|
|
|
\subsection{FSC-BT1035 (QCC3056)}
|
|
\label{sec:hw-val-bt1035}
|
|
|
|
\begin{table}[htbp]
|
|
\centering
|
|
\small
|
|
\begin{tabular}{@{}L{3.5cm}L{7.5cm}L{2.5cm}@{}}
|
|
\drhead Check & Requirement & Status \\
|
|
\midrule
|
|
UART with flow control & TX/RX + RTS/CTS wired & verified \\
|
|
I\textsuperscript{2}S init (firmware) &
|
|
\texttt{AT+AUXCFG=3}, \texttt{AT+I2SCFG=67} & driver rule \\
|
|
I\textsuperscript{2}S input & receives clocks from ADAU master (slave) & verified \\
|
|
Reset line & RESET (GPIO17) driven by ESP32 & verified \\
|
|
\bottomrule
|
|
\end{tabular}
|
|
\caption{FSC-BT1035 design checks (datasheets in \drpath{Hardware/DATASHEET/}).}
|
|
\label{tab:hw-val-bt1035}
|
|
\end{table}
|
|
|
|
\begin{drref}[Programming guide defaults]
|
|
Module defaults (Feasycom release 1.1.1): BR/EDR name \texttt{FSC-BT1035},
|
|
UART 115200/8/N/1, SSP on, auto-reconnect configurable via
|
|
\texttt{AT+AUTOCONN=0..15}. DigiRadio overrides the name from EEPROM identity
|
|
(\texttt{AT+NAME=<name>,0} disables the module MAC suffix).
|
|
\end{drref}
|
|
|
|
\subsection{System-level summary}
|
|
\label{sec:hw-val-summary}
|
|
|
|
\begin{table}[htbp]
|
|
\centering
|
|
\small
|
|
\begin{tabular}{@{}L{2.2cm}L{4.8cm}L{6.6cm}@{}}
|
|
\drhead Area & Item & Status \\
|
|
\midrule
|
|
Si4684 & RSTB pull-down, 1.8\,V rails, bypass caps, SPI & verified \\
|
|
Si4684 & RSTB release only in \texttt{Si4684Driver::boot()} & verified \\
|
|
ADAU1701 & clock loopback, master mode, 256$\times$f\textsubscript{S} & verified \\
|
|
ADAU1701 & I\textsuperscript{2}C 2\,k\(\Omega\) pull-ups (R1/R16) & verified \\
|
|
FSC-BT1035 & UART + flow control, I\textsuperscript{2}S slave & verified \\
|
|
Clocking & single 48\,kHz domain, ADAU master & verified \\
|
|
\bottomrule
|
|
\end{tabular}
|
|
\caption{Consolidated pre-fabrication validation status.}
|
|
\label{tab:hw-val-summary}
|
|
\end{table}
|
|
|
|
The consolidated pre-fabrication validation is complete for all
|
|
damage-class items (Si4684 power sequencing and supply levels) and the
|
|
shared I\textsuperscript{2}C bus.
|