Add updatable ADAU1701 program via flash partition and HTTP API.

Decouple the SigmaStudio RAM download from compiled-in adau1701_program.c:
DRAD v1 blobs in the dsp partition with embedded fallback, POST /api/dsp/program,
and host-tested blob parse/serialize helpers.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/docs/manual/ch-adau1701.tex

@@ -121,7 +121,7 @@ the DSP program and writes it into RAM after each reset.
     \node[step, fill=black!6, below=of rst] (i2c)
       {Create I\textsuperscript{2}C master @ 100\,kHz, address 0x34};
     \node[step, fill=black!8, below=of i2c] (dl)
-      {\texttt{default\_download\_IC\_1()} --- control, program, param RAM};
+      {Replay \texttt{DspProgram} from flash or embedded export};
     \node[step, fill=black!6, below=of dl] (ready)
       {\texttt{Adau1701Driver::isBooted()} = true};
     \node[step, fill=black!10, below=of ready] (prof)
@@ -135,7 +135,10 @@ the DSP program and writes it into RAM after each reset.
 \end{figure}
 
 \texttt{SIGMA\_WRITE\_REGISTER\_BLOCK} streams each write in 64-byte I\textsuperscript{2}C
-chunks. After download, \texttt{loadAndApply()} restores the saved
+chunks (payloads may exceed 255 bytes). The active script comes from the
+\texttt{dsp} data partition when a valid \texttt{DRAD} blob is present; otherwise
+the embedded SigmaStudio export is used (Section~\ref{sec:api-dsp-program}).
+After download, \texttt{loadAndApply()} restores the saved
 \texttt{core::AudioProfile} from NVS (or factory defaults) so user settings
 survive power cycles without re-writing the whole program.
 

Software/docs/manual/ch-api.tex

@@ -225,6 +225,26 @@ the ADAU1701 and writes NVS key \texttt{audio\_profile\_json}.
 HTTP status: \textbf{200 OK}; \textbf{400} for parse/validation failures;
 \textbf{500} when safeload or NVS persistence fails.
 
+\subsection{\texttt{POST /api/dsp/program}}
+\label{sec:api-dsp-program}
+
+Uploads a framed ADAU1701 RAM download blob (\texttt{DRAD} v1, see
+\texttt{core::parseDspProgramBlob()}). The body is raw bytes
+(\texttt{application/octet-stream} or any content type). On success the blob
+is written to the \texttt{dsp} flash partition and the device reboots; the
+next boot replays the new program before \texttt{loadAndApply()}.
+
+\begin{drnote}[Success response]
+\begin{drcode}[JSON]
+{"status":"stored","reboot_sec":3}
+\end{drcode}
+\end{drnote}
+
+HTTP status: \textbf{200 OK}; \textbf{400} with \texttt{\{"error":"..."\}}
+for invalid/truncated/CRC failures; \textbf{413} when the body exceeds
+200\,KiB; \textbf{500} on flash write failure. Pack blobs with
+\texttt{tools/pack\_dsp\_program.py} or \texttt{core::serializeDspProgramBlob()}.
+
 \subsection{\texttt{POST /api/audio/reset}}
 \label{sec:api-audio-reset}
 

Software/docs/manual/ch-classes.tex

@@ -183,6 +183,30 @@ audio control to safeload I\textsuperscript{2}C transactions without exposing
 parameter RAM addresses to services (Chapter~\ref{ch:adau1701},
 Section~\ref{sec:adau1701-stack}).
 
+\section{RegisterWrite}\label{cls:RegisterWrite}
+One SigmaStudio \texttt{SIGMA\_WRITE\_REGISTER\_BLOCK} step: 16-bit address
+plus payload bytes. Aggregated by \texttt{DspProgram}.
+
+\section{DspProgram}\label{cls:DspProgram}
+Ordered ADAU1701 RAM download script (pure domain). Parsed from a framed
+\texttt{DRAD} flash blob or built by \texttt{EmbeddedDspProgramSource}.
+
+\section{IDspProgramSource}\label{cls:IDspProgramSource}
+Port supplying \texttt{DspProgram} to \texttt{Adau1701Driver::boot()}.
+Implementations: flash partition, embedded export, and fallback composite.
+
+\section{EmbeddedDspProgramSource}\label{cls:EmbeddedDspProgramSource}
+Builds the factory \texttt{DspProgram} from \texttt{DigiRadio\_IC\_1.h}
+(five writes matching \texttt{default\_download\_IC\_1()}).
+
+\section{FlashDspProgramSource}\label{cls:FlashDspProgramSource}
+Reads and parses the \texttt{dsp} flash partition; \texttt{storeBlob()} erases
+and writes a validated blob from \texttt{POST /api/dsp/program}.
+
+\section{FallbackDspProgramSource}\label{cls:FallbackDspProgramSource}
+Tries \texttt{FlashDspProgramSource} first, then
+\texttt{EmbeddedDspProgramSource} when the partition is empty or invalid.
+
 % ------------------------------------------------------------------
 % Domain core — audio (Slice 5)
 % ------------------------------------------------------------------