esp-idf/examples/peripherals/ledc/ledc_basic/README.md
2022-07-14 08:26:32 +08:00

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| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-S2 | ESP32-S3 |
| ----------------- | ----- | -------- | -------- | -------- | -------- |
# _LEDC Basic Example_
(See the README.md file in the upper level 'examples' directory for more information about examples.)
This example shows how to use the LEDC to generate a PWM signal using the `LOW SPEED` mode.
To use `HIGH SPEED` mode check if the selected SoC supports this mode.
## How to use example
### Hardware Required
* A development board with any Espressif SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.)
* A USB cable for power supply and programming
Connect the GPIO to an oscilloscope to see the generated signal:
|ledc channel| GPIO |
|:----------:|:-----:|
| Channel 0 | GPIO5 |
### Configure the project
The example uses fixed PWM frequency of 5 kHz, duty cycle in 50%, and output GPIO pin. To change them, adjust `LEDC_FREQUENCY`, `LEDC_DUTY`, `LEDC_OUTPUT_IO` macros at the top of ledc_basic_example_main.c.
Depending on the selected `LEDC_FREQUENCY`, you will need to change the `LEDC_DUTY_RES`.
To dinamicaly set the duty and frequency, you can use the following functions:
To set the frequency to 2.5 kHZ i.e:
```c
ledc_set_freq(LEDC_MODE, LEDC_TIMER, 2500);
```
Now the duty to 100% i.e:
```c
ledc_set_duty(LEDC_MODE, LEDC_CHANNEL, 8191);
ledc_update_duty(LEDC_MODE, LEDC_CHANNEL);
```
To change the duty cycle you need to calculate the duty range according to the duty resolution.
If duty resolution is 13 bits:
Duty range: `0 to (2 ** 13) - 1 = 8191` where 0 is 0% and 8191 is 100%.
### Build and Flash
* [ESP-IDF Getting Started Guide](https://idf.espressif.com/)
Build the project and flash it to the board, then run monitor tool to view serial output:
```bash
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
Running this example, you will see the PWM signal with a duty cycle of 50%.
![PWM](image/ledc_pwm_signal.png)
## Troubleshooting
* Duty Resolution
* If you get the following error log `ledc: requested frequency and duty resolution can not be achieved, try reducing freq_hz or duty_resolution.` you need to change the `LEDC_DUTY_RES` to a lower resolution and change the range of the duty.
* Programming fail
* Hardware connection is not correct: run `idf.py -p PORT monitor`, and reboot your board to see if there are any output logs.
* The baud rate for downloading is too high: lower your baud rate in the `menuconfig` menu, and try again.
For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you soon.