| Supported Targets | ESP32-C3 | ESP32-C5 | ESP32-C6 | ESP32-H2 | ESP32-H21 | ESP32-H4 | ESP32-P4 | ESP32-S3 | ESP32-S31 |
| ----------------- | -------- | -------- | -------- | -------- | --------- | -------- | -------- | -------- | --------- |

# UART OTA Example

This example demonstrates how to use UART to perform an Over-the-Air (OTA) firmware update on an ESP32-based device. It transfers firmware data via UART using DMA and applies the update seamlessly.

## How to use example

### Hardware Required

The example can be run on any development board, that is based on the Espressif SoC. The board shall be connected to a computer with a single USB cable for flashing and monitoring. The external interface should have 3.3V outputs. You may use e.g. 3.3V compatible USB-to-Serial dongle.

### Software Required

1. Partition Table:

The example requires a valid partition table with an OTA partition. Update your partitions.csv or equivalent partition table to include an OTA data partition. Below is an example of a partition table with OTA support:

```
# Name,   Type, SubType, Offset,   Size, Flags
nvs,      data, nvs,     0x9000,   0x6000,
factory,  app,  factory, 0x10000,  1M,
ota_0,    app,  ota_0,   0x110000, 1M,
ota_1,    app,  ota_1,   0x210000, 1M,
```

You can also use `CONFIG_PARTITION_TABLE_TWO_OTA_LARGE` if you don't want to define a partition table by yourself.

2. Firmware Binary:

Prepare the firmware binary (.bin file) you want to flash via OTA. This binary should be compatible with the ESP32 platform and must match the partition table configuration.
Example:

*1.* Build the firmware binary via:

```
idf.py build
```

*2.* Locate the binary file in the build/ directory (e.g., build/your_project.bin)

### Setup the Hardware

Connect the external serial interface to the board as follows.

```

                    +-------------------+                          +-------------------+
                    |   ESP Chip        |                          | External UART Pin |
                    |   Interface       |                          |                   |
                    +-------------------+                          +-------------------+
                            |                                            |
                            |                                            |
Receive Data (RxD):         + GPIO9 <------------------------------> TxD + 
                            |                                            |
Ground:                     + GND <--------------------------------> GND +
                            |                                            |

```

### Configure the project

Use the command below to configure project using Kconfig menu as showed in the table above.
The default Kconfig values can be changed such as: UART_BAUD_RATE, UART_PORT_NUM, UART_RX_IO (Refer to Kconfig file).

```
idf.py menuconfig
```

### Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

```
idf.py -p PORT flash monitor
```

Then transmit the prepared bin to ESP-chips. This example uses `uhci_start_receive_continuous()`, so the DMA keeps running across UART idle gaps and no data is dropped between frames. The transfer is considered finished once the RX line stays idle for about one second (`UART_DMA_OTA_IDLE_TIMEOUT_MS`), so make sure the whole bin is sent without such a long pause in the middle.

(To exit the serial monitor, type ``Ctrl-]``.)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

## Example Output

```
I (277) main_task: Started on CPU0
I (287) main_task: Calling app_main()
I (287) uhci-example: UHCI initialized
I (447) uhci-example: OTA process started
I (18047) uhci-example: Received size: 150032
I (18047) uhci-example: Total received size: 150032
I (18047) esp_image: segment 0: paddr=001d0020 vaddr=3c020020 size=06748h ( 26440) map
I (18057) esp_image: segment 1: paddr=001d6770 vaddr=3fc8b400 size=0111ch (  4380)
I (18067) esp_image: segment 2: paddr=001d7894 vaddr=40380000 size=08784h ( 34692)
I (18077) esp_image: segment 3: paddr=001e0020 vaddr=42000020 size=11d98h ( 73112) map
....
I (18147) uhci-example: OTA update successful. Rebooting...
.... (the following part depends on your bin, this output depends on example/get-started/hello_world)
I (268) sleep_gpio: Enable automatic switching of GPIO sleep configuration
I (275) main_task: Started on CPU0
I (275) main_task: Calling app_main()
Hello world!
This is esp32c3 chip with 1 CPU core(s), WiFi/BLE, silicon revision v0.4, 4MB external flash
Minimum free heap size: 333524 bytes
Restarting in 10 seconds...
Restarting in 9 seconds...
Restarting in 8 seconds...
```