esp-idf/examples/peripherals/ledc/ledc_basic/README.md

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:

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

• ESP-IDF Getting Started Guide

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%.

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.