DSP-ADAU1467

ModulosDSP — ESP32-S3 WiFi Bridge for ADAU14xx DSP

An Arduino sketch for the Waveshare ESP32-S3 Zero that provides a WiFi interface to Analog Devices ADAU1401/1701 DSP chips:

• SigmaTCP bridge (port 8086) — lets SigmaStudio connect wirelessly to a physical DSP over I²C
• HTTP EEPROM uploader (port 80, path /) — flash DSP firmware binaries to a 24C256 EEPROM from a browser
• HTTP OTA updater (port 80, path /ota) — update the ESP32 firmware itself over WiFi

This sketch runs on the companion MSD ADAU14-1701 Adapter PCB.

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Hardware

Component	Part	Notes
Microcontroller	Waveshare ESP32-S3 Zero	Onboard WS2812 NeoPixel on GPIO 21
DSP	ADAU1401 / ADAU1701	I²C address 0x68 (7-bit: 0x34)
EEPROM	24C256 (32 KB)	I²C address 0xA0 (7-bit: 0x50)
Display	20×4 hd44780 I²C LCD	Boot status and IP address (optional)

Pin Assignments

Signal	GPIO
I²C SDA	13
I²C SCL	12
Status LED (NeoPixel)	21 (built-in)

The DSP, EEPROM, and LCD all share the same I²C bus at 400 kHz. The LCD is optional — if not detected at boot the sketch continues without it.

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Arduino Libraries Required

Install via Sketch → Include Library → Manage Libraries:

Library	Purpose
WiFi	ESP32 WiFi (built-in with ESP32 core)
WebServer	HTTP server (built-in)
Wire	I²C master (built-in)
Update	OTA flash write (built-in with ESP32 core)
LittleFS	Embedded filesystem for web assets (built-in)
Adafruit NeoPixel	WS2812 status LED
hd44780	I²C LCD driver

Board: select ESP32S3 Dev Module (or Waveshare ESP32-S3 Zero if your board package includes it) via the ESP32 Arduino core.

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Configuration

WiFi Credentials

Credentials are stored in NVS (non-volatile flash) using the Preferences library — there are no hardcoded SSID or password in the source code.

First boot / no credentials stored:

1. The device starts a SoftAP named ModulosDSP-Setup (open, no password).
2. Connect your phone or laptop to ModulosDSP-Setup.
3. Open http://192.168.4.1 in a browser — a setup page appears.
4. Enter your WiFi SSID and password and click Save & Connect.
5. The device saves the credentials to NVS and reboots, joining your network.

If the connection fails (wrong password, network out of range) the device falls back to AP mode automatically.

Resetting credentials: on the Device Management page (/ota) click Reset WiFi Credentials. The device clears NVS and reboots into AP mode.

Hostname

const char* hostname = "modulos-dsp";   // resolves as modulos-dsp.local

The hostname is the only compile-time network constant. It is registered via mDNS (Bonjour/Zeroconf), so once on the network the device is reachable at modulos-dsp.local. Change it if you run more than one unit on the same network.

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Status LED

The onboard NeoPixel (GPIO 21) shows current activity at a glance:

Color	Meaning
Off	Idle — no TCP client connected
Green	DSP write in progress (SigmaTCP)
Blue	DSP read in progress (SigmaTCP)
Yellow	EEPROM write via SigmaTCP
Magenta	EEPROM upload via HTTP
Cyan	OTA firmware flash in progress
Red flash	Error (I²C failure, buffer overflow, bad packet)

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Using with SigmaStudio

1. Power on the board. The LCD displays the assigned IP address; Serial (115200 baud) also prints it alongside the mDNS hostname.
2. In SigmaStudio, open Settings → Hardware Configuration.
3. Add a USBi interface and switch the connection type to SigmaTCP.
4. Enter modulos-dsp.local (or the IP address) and port 8086.
5. Click Link → Compile Download — SigmaStudio pushes firmware to the DSP wirelessly.

Sessions that go idle for 30 seconds are closed automatically, freeing the bridge for a new connection.

The bridge handles both direct writes and safeload writes (glitch-free atomic parameter updates on a live DSP). If the connection drops mid-safeload, any partial pending slots are flushed to parameter RAM on disconnect so the DSP's internal safeload counter is clean for the next session.

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EEPROM Uploader (Web UI)

Navigate to http://<ESP32-IP>/ in any browser:

1. Click Choose File and select a SigmaStudio-exported binary.
2. Optionally tick Verify (CRC32) to read back and confirm the write.
3. Click Upload — the Magenta LED pulses during the write.

The 24C256 holds 32 KB. The DSP reads this EEPROM at power-up via its SELFBOOT pin, allowing standalone operation without the ESP32 actively driving it.

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Device Management (/)

The main page at http://modulos-dsp.local/ is the device management hub:

DSP Status — live card polling GET /dsp_status every 2 seconds:

Field	Register	Description
Core Register	0x081C	Full 16-bit register value (hex)
Running	Core Register bit 0	Green badge when DSP is executing
GPIO	0x0808	GPIO All Register value (hex)
ADC 0–3	0x0809–0x080C	Raw ADC input values (hex)

EEPROM Upload — flash DSP firmware to the 24C256:

1. Click Choose File and select a SigmaStudio-exported binary.
2. Optionally tick Verify (CRC32) to read back and confirm the write.
3. Click Upload and Program — the Magenta LED pulses during the write.

DSP Control — click Soft Reset DSP to restart DSP execution without reloading from EEPROM.

GPIO Control — GP0–GP3 toggle buttons write to GPIO All Register (0x0808). Buttons go green when the pin is high. Output-only pins respond (configured via MpCfg registers).

WiFi Settings — click Reset WiFi Credentials to clear NVS and reboot into AP setup mode.

Firmware Update — link to the OTA page (/ota) for flashing new ESP32 firmware.

Firmware Update Page (/ota)

Navigate to http://modulos-dsp.local/ota to flash new ESP32 firmware:

1. In Arduino IDE, export the compiled binary: Sketch → Export Compiled Binary (produces a .bin file).
2. Click Choose File and select the .bin.
3. Click Flash Firmware — the Cyan LED indicates the write is in progress.
4. On success the device reboots automatically. The page redirects to / after 5 seconds.

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How It Works

SigmaTCP Bridge

SigmaTCP is the protocol used by Analog Devices' SigmaStudio to talk to hardware like the USBi programmer. This sketch implements the server side over TCP/WiFi and forwards all register traffic to the DSP or EEPROM via I²C.

WRITE (opcode 0x09):

• 10-byte header: command, safeload flag, placement, totalLen, chipAddr, dataLen, startAddress
• totalLen is validated against WRITE_HDR_LEN + dataLen before buffering — mismatched packets drop the connection
• Payload forwarded to DSP or EEPROM via I²C
• I²C errors are reported in the 4-byte ACK {0x09, 0x00, 0x04, status} so SigmaStudio sees real write failures

READ (opcode 0x0A):

• 8-byte header: command, totalLen, chipAddr, dataLen, startAddress
• I²C data read in 32-byte chunks
• 6-byte response header (0x0B, totalLen_hi, totalLen_lo, status, dataLen_hi, dataLen_lo) + payload sent back
• On I²C failure, zeros are sent rather than dropping the connection (allows SigmaStudio to probe an unresponsive DSP)

Safeload: When the safeload flag is set, parameters are queued into the DSP's 5 hardware safeload slots and committed atomically by writing 0x003C to the Core Register. This avoids audio clicks when updating parameters on a running DSP. Any pending safeload slots are flushed at both the start and end of every TCP session to keep the DSP's internal counter in sync.

The TCP receive loop drains all available bytes into a 50 KB buffer every iteration (keeping the TCP receive window open), then processes complete packets from the buffer. This correctly handles large program downloads that span multiple TCP segments.

WiFi Watchdog

The sketch monitors WiFi status every 5 seconds. If the connection drops it attempts WiFi.reconnect() on each check. On recovery it restarts the TCP server socket and updates the LCD with the current IP address.

EEPROM Writes

Writes are chunked to ≤28 bytes, aligned to 64-byte page boundaries. After each chunk, the firmware polls the EEPROM for ACK (up to 120 ms) to wait for its internal write cycle before continuing.

Fixed-Point Format

The ADAU1401 uses 5.23 fixed-point for parameter RAM (4 bytes per word). Safeload registers add a leading 0x00 padding byte, making them 5 bytes. The DataConversion class handles conversion from float, int32_t, and other C types.

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File Structure

ModulosDSP_101/
├── ModulosDSP_101.ino   Main sketch: WiFi, TCP/HTTP servers, I²C bridge
├── DSPWriter.h          DSP register write interface and address map
├── DSPWriter.cpp        I²C write and safeload implementations
├── DataConversion.h     5.23 fixed-point conversion declarations
├── DataConversion.cpp   Fixed-point conversion implementations
├── index_html.h         Main device management UI (DSP status, EEPROM upload, controls)
├── ota_html.h           OTA firmware flash form
└── ap_html.h            SoftAP WiFi config portal (first-boot / failed-connect)

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ADAU1401 Address Map

Region	Address Range	I²C bytes per register
Parameter RAM	0x0000–0x03FF	4
Program RAM	0x0400–0x07FF	5
Interface Registers 0–7	0x0800–0x0807	1
GPIO Register	0x0808	1
ADC 0–3 (read-only)	0x0809–0x080C	1
Safeload Data 0–4	0x0810–0x0814	5
Safeload Address 0–4	0x0815–0x0819	2
Core Register	0x081C	2 (R0 reset)
MpCfg 0–1	0x0820–0x0821	1
Analog Power Down	0x0822	1
Analog Interface 0	0x0824	1

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Build / Version

The build identifier uses YYMMDD_rev format (e.g. 260304_13 = 4 March 2026, revision 13). It is displayed on the LCD and printed to Serial at boot. When cutting a new build, update both the file header comment and the version constant in ModulosDSP_101.ino.

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References

• SigmaStudio TCP interface for ESP32 — Analog Devices forum
• roTDSP — ADAU1401 carrier board
• SigmaDSP Arduino library (MCUdude)
• Elektor AudioDSP — ESP32 + ADAU1701
• How to program an Analog Devices DSP