micheleandCursor
d49b2011dd
Implement Bt1035Driver AT init (AT+AUXCFG=1), core AT parser with host tests, wire boot into HardwareBootstrap, and document DAB/FM tuning workflows in ch-si4684. Co-authored-by: Cursor <cursoragent@cursor.com>
240 lines
8.6 KiB
TeX
240 lines
8.6 KiB
TeX
% ============================================================
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% DigiRadio — Manual chapter: FSC-BT1035 Bluetooth
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% ============================================================
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\chapter{FSC-BT1035 Bluetooth Transmitter}
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\label{ch:bt1035}
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The Feasycom FSC-BT1035 (Qualcomm QCC3056) is the wireless output stage of
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DigiRadio: it receives PCM from the ADAU1701 over I\textsuperscript{2}S and
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streams Bluetooth audio with aptX, aptX~HD, and aptX~Adaptive. This chapter
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documents how the ESP32-S3 controls the module over UART (AT commands with
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RTS/CTS), why Line-In mode is mandatory, and how \texttt{bt1035::Bt1035Driver}
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implements the bring-up sequence.
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\begin{drref}[Hardware context]
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Board wiring (UART pins, I\textsuperscript{2}S to the module, flow control)
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is in Chapter~\ref{ch:hardware}, Section~\ref{sec:hw-bt1035}. The ADAU1701
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master clock and limiter settings that feed the module are in
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Chapter~\ref{ch:adau1701} and Chapter~\ref{ch:sigmastudio}.
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\end{drref}
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\section{Role in the audio chain}
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\label{sec:bt1035-role}
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The BT1035 is an I\textsuperscript{2}S \textbf{slave} at 48\,kHz: LRCLK and
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BCLK come from the ADAU1701; PCM arrives on \texttt{SDATA\_OUT0}
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(ADAU MP6 $\rightarrow$ module pin~5). The ESP32 does not process audio
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samples for Bluetooth; it only configures the module so the wired path is
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accepted and encoded for transmission.
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Without firmware init the module may stay in a default mode that ignores the
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Line-In from the DSP. The mandatory \texttt{AT+AUXCFG=1} command selects
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auxiliary/Line-In input --- omitting it silently breaks the entire wireless
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output (Section~\ref{sec:bt1035-linein}).
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\section{Control interface}
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\label{sec:bt1035-uart}
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\subsection{UART parameters}
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}ll@{}}
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\drhead Setting & Value \\
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\midrule
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Port & UART2 (not the console UART) \\
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Baud rate & 115200 \\
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Data format & 8N1 \\
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Flow control & Hardware RTS/CTS (required) \\
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Reset & GPIO active-low pulse at boot \\
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SYS\_CTL & Held active to enable the module \\
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\bottomrule
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\end{tabular}
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\caption{FSC-BT1035 UART and control lines (\texttt{board\_pins.hpp}).}
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\label{tab:bt1035-uart}
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\end{table}
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\subsection{Response handling}
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Every command expects a module reply containing \texttt{OK} or
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\texttt{ERROR}. The driver:
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\begin{itemize}
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\item builds lines in the pure core via \texttt{core::buildBt1035AtLine()};
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\item classifies replies with \texttt{core::parseBt1035AtResponse()};
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\item treats timeouts and unexpected payloads as errors (never ignored).
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\end{itemize}
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Host tests in \texttt{components/core/test/bt1035\_at\_test.cpp} lock the
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init sequence (including \texttt{AT+AUXCFG=1}) and the parser.
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\section{Mandatory Line-In mode}
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\label{sec:bt1035-linein}
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\begin{drcaution}[AT+AUXCFG=1 is not optional]
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The documented init sequence must include \texttt{AT+AUXCFG=1} after a
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successful \texttt{AT} ping. This tells the QCC3056 firmware to take audio
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from the wired I\textsuperscript{2}S/Line-In port (the ADAU1701 output)
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rather than an internal source. AGENTS.md and the hardware manual both treat
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skipping this step as a production bug.
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\end{drcaution}
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\section{Boot sequence}
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\label{sec:bt1035-boot}
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At power-up \texttt{HardwareBootstrap::boot()} runs the Si4684 and ADAU1701
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first, applies the saved audio profile, then initialises the BT1035 so the
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Line-In path is ready before Wi-Fi starts.
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\begin{figure}[htbp]
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\centering
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\begin{tikzpicture}[
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step/.style={draw, rounded corners, minimum width=9.5cm,
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minimum height=0.9cm, align=center, font=\small},
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>={Latex}, node distance=3mm]
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\node[step, fill=black!6] (sys) {SYS\_CTL high, RESET\# pulse};
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\node[step, fill=black!6, below=of sys] (uart)
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{Install UART2 @ 115200, RTS/CTS};
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\node[step, fill=black!8, below=of uart] (at)
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{Send \texttt{AT} --- expect OK};
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\node[step, fill=black!10, below=of at] (aux)
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{Send \texttt{AT+AUXCFG=1} --- expect OK (Line-In)};
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\node[step, fill=black!6, below=of aux] (done)
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{\texttt{Bt1035Driver::isBooted()} = true};
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\foreach \a/\b in {sys/uart, uart/at, at/aux, aux/done} {
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\draw[->] (\a) -- (\b);
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}
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\end{tikzpicture}
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\caption{FSC-BT1035 AT init on DigiRadio.}
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\label{fig:bt1035-boot}
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\end{figure}
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Pairing, codec selection, and volume over Bluetooth are handled by the
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module's own firmware and NVS; DigiRadio firmware currently implements
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only the Line-In bring-up required for the wired audio path.
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\section{Software architecture}
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\label{sec:bt1035-stack}
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}llp{5.8cm}@{}}
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\drhead Layer & Type & Responsibility \\
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\midrule
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Bootstrap & \texttt{HardwareBootstrap} &
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Constructs driver, calls \texttt{boot()} after ADAU1701 \\
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Driver & \texttt{bt1035::Bt1035Driver} &
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UART, reset, AT init sequence \\
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Pure core & \texttt{core::Bt1035AtCommand}, parser &
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Host-testable command strings and OK/ERROR classification \\
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\bottomrule
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\end{tabular}
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\caption{BT1035 control stack (Slice~6). Future HTTP/UI for pairing will
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sit above the driver without changing the init contract.}
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\label{tab:bt1035-stack}
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\end{table}
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\section{Supported AT command subset}
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\label{sec:bt1035-at}
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The firmware enumerates every command it sends. Extending the subset requires
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updating \texttt{core::Bt1035AtCommand}, the manual, and a host test.
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}lll@{}}
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\drhead Enum & Line sent & Purpose \\
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\midrule
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\texttt{Ping} & \texttt{AT} & Verify UART link \\
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\texttt{AuxLineIn} & \texttt{AT+AUXCFG=1} & Enable Line-In from ADAU \\
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\bottomrule
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\end{tabular}
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\caption{AT commands used at boot (\texttt{core::bootInitSequence()}).}
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\label{tab:bt1035-at}
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\end{table}
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\section{Bt1035Driver API}
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\label{sec:bt1035-driver}
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\texttt{Bt1035Driver} owns UART and GPIO reset. All methods return
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\texttt{std::expected<T, Bt1035Error>}.
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\begin{table}[htbp]
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\centering
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\begin{tabular}{@{}ll@{}}
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\toprule
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\textbf{Method} & \textbf{Purpose} \\
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\midrule
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\texttt{boot()} & Reset, UART init, run \texttt{bootInitSequence()} \\
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\texttt{isBooted()} & \texttt{true} after Line-In init succeeded \\
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\texttt{sendCommand(cmd)} & Send one typed command, expect OK \\
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\bottomrule
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\end{tabular}
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\caption{Public driver API.}
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\label{tab:bt1035-api}
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\end{table}
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\subsection{Error codes}
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\begin{table}[htbp]
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\centering
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\small
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\begin{tabular}{@{}ll@{}}
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\drhead \texttt{Bt1035Error} & Typical cause \\
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\midrule
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\texttt{ResetFailed} & GPIO configuration failure \\
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\texttt{UartInitFailed} & \texttt{uart\_driver\_install} / pins \\
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\texttt{NotBooted} & \texttt{sendCommand} before \texttt{boot()} \\
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\texttt{AtTimeout} & No OK/ERROR within 2\,s \\
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\texttt{AtError} & Module returned ERROR \\
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\texttt{UnexpectedResponse} & Unrecognised payload (future use) \\
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\bottomrule
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\end{tabular}
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\caption{Driver error enumeration.}
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\label{tab:bt1035-errors}
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\end{table}
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\section{Integration at power-up}
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\label{sec:bt1035-integration}
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\texttt{main/hardware\_bootstrap.cpp} constructs a static
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\texttt{Bt1035Driver} and calls \texttt{boot()} after
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\texttt{AudioService::loadAndApply()}. Failure returns
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\texttt{HardwareBootError::Bt1035BootFailed} and \texttt{app\_main} halts
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before network bring-up (fail-closed, same as Si4684/ADAU1701).
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Boot order:
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\begin{enumerate}
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\item Si4684 \texttt{boot(Dab)} --- tuner image in RAM.
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\item ADAU1701 \texttt{boot()} --- SigmaStudio program in RAM.
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\item \texttt{AudioService::loadAndApply()} --- user mixer/EQ profile.
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\item BT1035 \texttt{boot()} --- Line-In enabled for wireless output.
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\end{enumerate}
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\section{Typical usage (firmware developer)}
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\label{sec:bt1035-usage}
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After a successful \texttt{HardwareBootstrap::boot()}, the module is ready;
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no further calls are required for basic listening. To re-send Line-In config
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after a module reset:
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\begin{verbatim}
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bt1035::Bt1035Driver& bt = ...;
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if (auto r = bt.sendCommand(core::Bt1035AtCommand::AuxLineIn); !r) {
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// handle Bt1035Error
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}
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\end{verbatim}
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\section{Further reading}
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\label{sec:bt1035-reading}
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\begin{itemize}
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\item Feasycom FSC-BT1035 AT command manual (vendor) --- full command set
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for pairing, name, and codec options not yet wrapped by firmware.
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\item Chapter~\ref{ch:hardware} --- pin map and I\textsuperscript{2}S routing.
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\item Chapter~\ref{ch:adau1701} --- DSP output that feeds the module.
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\item \texttt{components/core/test/bt1035\_at\_test.cpp} --- init sequence test.
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\end{itemize}
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