RotaryCell / build guide

Upload the firmware

The first installation is made through the LilyGO's ESP-USB connector using Arduino IDE. The modem's USB connector is not used for this step. Once a full image has been installed, later application updates can also be loaded through the maintenance web page.

This walkthrough uses Arduino IDE 2.3.10, Espressif's ESP32 Arduino core 3.3.11, and the ESP32S3 Dev Module target. The RotaryCell sketch uses only libraries supplied with that ESP32 core, so no additional Arduino libraries are required.

1. Install the ESP32 board package

Install Arduino IDE 2.x, open Tools → Board → Boards Manager, and install version 3.3.11 of esp32 by Espressif Systems.

Download the firmware source and open the .ino file from its complete versioned folder. Arduino IDE should show the other .cpp and .h files as tabs alongside the sketch; keep the whole folder together.

The currently tested PCB build uses ESP-RotaryCell_v0.11.1-dev. The repository also keeps the current stable release under firmware/current.

2. Connect the controller

Connect a data-capable USB cable to the LilyGO port marked ESP-USB. Select the new serial port in Arduino IDE, then choose ESP32S3 Dev Module as the board.

Use these settings under Tools:

Setting	Selection
USB CDC On Boot	Enabled
CPU Frequency	240 MHz (WiFi)
Core Debug Level	None
USB DFU On Boot	Disabled
Erase All Flash Before Sketch Upload	Disabled
Events Run On	Core 1
Flash Mode	QIO 80 MHz
Flash Size	16 MB (128 Mb)
JTAG Adapter	Disabled
Arduino Runs On	Core 1
USB Firmware MSC On Boot	Disabled
Partition Scheme	Minimal SPIFFS (1.9 MB APP with OTA / 128 KB SPIFFS)
PSRAM	Disabled
Upload Mode	UART0 / Hardware CDC
Upload Speed	921600
USB Mode	Hardware CDC and JTAG
Zigbee Mode	Disabled

Arduino IDE Tools menu with the ESP32-S3 board and upload settings selected

3. Compile and upload

Click Verify first. A successful build ends with the program-storage and dynamic-memory summaries rather than an error message.

Arduino IDE after successfully compiling the RotaryCell firmware

Click Upload. Arduino IDE compiles again, connects to the ESP32-S3, writes the image and verifies it. Wait for both Hash of data verified and Hard resetting via RTS pin before disconnecting anything.

Completed USB firmware upload with the written image verified

4. Watch the first boot

Open Tools → Serial Monitor, select 115200 baud, and set the line ending to Both NL & CR. The controller should report the handset state, start the A7670G interface and print the console command list.

First serial output after the uploaded firmware starts

The modem may take roughly a minute to initialize and register. Network events will continue to appear in the Serial Monitor. Once network time is available, the log changes from elapsed-time stamps such as [+0:01:02] to dated stamps.

Modem registration events followed by cellular network time synchronization

Enter S and press Send for a complete status report. A ready installation should show:

the correct on-hook or off-hook handset state;
UART response: ONLINE;
SIM: READY;
a registered cellular state and an operator name; and
a plausible battery voltage.

Complete status report from a running RotaryCell controller

The firmware can be uploaded with USB power alone, but the finished telephone cannot be tested that way. The AG1171 carrier is supplied from the LilyGO's battery path, so connect the battery before testing hook detection, rotary dialing, ringing or audio.

At the console, ? prints the available commands, P enables verbose rotary pulse display, and WIFI opens the maintenance Wi-Fi without using the dial.