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esp-idf/examples/peripherals/ledc/ledc_basic/README.md
pedro.minatel a6798eac98 Added LEDC basic PWM example 
Changes on the ledc_init function
Review on the README, docs and example functions
Added how to set freq and duty on README
Fix on the ledc.rst docs in the App Example
Added new example reference in the Chinese docs
2021-04-28 11:11:07 +01:00

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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 ESP32, ESP32-S2, ESP32-C3 or ESP32-S3 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:

ledc_set_freq(LEDC_MODE, LEDC_TIMER, 2500);

Now the duty to 100% i.e:

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

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.