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esp-idf/examples/peripherals/ledc/ledc_basic/README.md
Song Ruo Jing c0a1d27858 fix(ledc): fix ledc driver 100% duty cycle configuration 
Update ledc duty cycle value range in doxygen.
Fix duty configuration error at 100% duty cycle for ESP32.
Improve LEDC API doxygen.

Closes https://github.com/espressif/esp-idf/pull/11516
Closes https://github.com/espressif/esp-idf/issues/12593
Closes https://github.com/espressif/esp-idf/issues/12083
2023-11-22 03:12:38 +00:00

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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 dynamically set the duty and frequency, you can use the following functions:

To set the frequency to 2.5 kHZ i.e:

ledc_set_freq(LEDC_MODE, LEDC_TIMER, 2500);

Now set the duty to 100% i.e:

ledc_set_duty(LEDC_MODE, LEDC_CHANNEL, 8192);
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) = 8192 where 0 is 0% and 8192 is 100%.

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

Running this example, you will see the PWM signal with a duty cycle of 50%.

PWM

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 on GitHub. We will get back to you soon.