USB to UART Bridge

USB to serial bridge tool using the USB and UART capabilities of the ESP32-S2/S3 microcontroller. This tool serves as a debugging and downloading utility with the following features:

1. Bidirectional transparent data communication between USB and UART.
2. Configurable serial port settings (supports baud rates up to 3000000 bps).
3. Compatibility with automatic firmware download functionality for esptool, enabling firmware updates for other ESP SoCs.

/*
 *                                │
 *                                │USB
 *                                │
 *                                ▼
 *                            ┌──────┐
 *                            │      │
 *                            │ O  O │
 *                            │      │
 *                        ┌───┴──────┴───┐
 *                        │              │
 * ┌───────────┐          │ ESP32-S3-OTG │
 * │           │          │              │
 * │           │ RX       │ ┌──┐         │
 * │           │◄─────────┼─┤  │expend IO│
 * │           │ TX       │ │  │         │
 * │Target_MCU │◄─────────┼─┤  │         │
 * │           │ IO0      │ │  │         │
 * │           │◄─────────┼─┤  │         │
 * │           │ EN       │ │  │         │
 * │           │◄─────────┼─┤  │         │
 * │           │          │ └──┘         │
 * └───────────┘          │              │
 *                        │              │
 *                        │              │
 *                        └───┬──────┬───┘
 *                            │ [  ] │
 *                            └──────┘
 */

Default IO Configuration

The example using ESP32-S3-OTG board by default, the IO configuration is as follows:

ESP32-Sx IO	Function	Remark
20	USB D+	Fixed
19	USB D-	Fixed
46	UART-RX	Link to target board TX
45	UART-TX	Link to target board RX
26	Boot(IO0)	Link to target board Boot(IO0)
3	EN (RST)	Link to target board EN(RST)

Build and Flash

1. Make sure ESP-IDF is setup successfully

2. Set up the ESP-IDF environment variables, please refer Set-up the environment variables, Linux can use:

   . $HOME/esp/esp-idf/export.sh

3. Set ESP-IDF build target to esp32s2 or esp32s3

   idf.py set-target esp32s3

4. Build, Flash, output log

   idf.py build flash monitor -D ADAPTER_USB_MANUFACTURER_OVERRIDE="Nabu Casa" -D ADAPTER_USB_PRODUCT_OVERRIDE="ZWA-2"

Automatic Firmware Download with esptool

• The automatic download feature is enabled by default. You can disable this option in menuconfig → USB UART Bridge Demo → Enable auto download.
• When using the automatic download feature, connect the development board's AUTODLD_EN_PIN and AUTODLD_BOOT_PIN pins to the target MCU's IO0 (Boot) and EN (RST) pins respectively.
• The automatic download feature may not function correctly on certain development boards (due to delays caused by RC circuits). In such cases, please fine-tune the code with gpio_set_level software delays.

Wireless USB UART Bridge

Please refer to Wireless USB UART Bridge.