mirror of
https://github.com/espressif/esp-idf.git
synced 2024-10-05 20:47:46 -04:00
72 lines
2.6 KiB
Markdown
72 lines
2.6 KiB
Markdown
| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-C6 | ESP32-H2 | ESP32-P4 | ESP32-S2 | ESP32-S3 |
|
|
| ----------------- | ----- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
|
|
|
|
# UART Select Example
|
|
|
|
(See the README.md file in the upper level 'examples' directory for more information about examples.)
|
|
|
|
The UART select example is for demonstrating the use of `select()` for
|
|
synchronous I/O multiplexing on the UART interface. The example waits for a
|
|
character from UART using `select()` until a blocking read without delay or a
|
|
successful non-blocking read is possible.
|
|
|
|
Please note that the same result can be achieved by using `uart_read_bytes()`
|
|
but the use of `select()` allows to use it together with other virtual
|
|
file system (VFS) drivers, e.g. LWIP sockets.
|
|
|
|
This example can be used to develop applications for non-blocking read and write from/to various sources (UART,
|
|
sockets, ...) where a ready resource can be served without being blocked by a busy resource.
|
|
|
|
For a more comprehensive example please refer to `system/select`.
|
|
|
|
## 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 communication through UART.
|
|
|
|
### Configure the project
|
|
|
|
```
|
|
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
|
|
```
|
|
|
|
(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
|
|
|
|
You can see a similar output after flashing and monitoring the application:
|
|
|
|
```
|
|
...
|
|
I (276) cpu_start: Pro cpu start user code
|
|
I (294) cpu_start: Starting scheduler on PRO CPU.
|
|
I (0) cpu_start: Starting scheduler on APP CPU.
|
|
I (10295) uart_select_example: Timeout has been reached and nothing has been received
|
|
I (15295) uart_select_example: Timeout has been reached and nothing has been received
|
|
I (20295) uart_select_example: Timeout has been reached and nothing has been received
|
|
```
|
|
|
|
You can push any key on your keyboard to see the result of a successful detection by `select()` and subsequent
|
|
blocking read (without delay). The following output shows the result of pushing `a` on the keyboard:
|
|
|
|
```
|
|
...
|
|
I (15295) uart_select_example: Timeout has been reached and nothing has been received
|
|
I (20295) uart_select_example: Timeout has been reached and nothing has been received
|
|
I (20945) uart_select_example: Received: a
|
|
I (25955) uart_select_example: Timeout has been reached and nothing has been received
|
|
...
|
|
```
|