ESP8266 datasheet(98/117 Pages) ESPRESSIF

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12. PWM Interface

12.1.3. Conﬁguration

•

In timing interrupt, to exist the program as soon as possible, timing parameters of the

next period of PWM waveform can be loaded when PWM period started.

•

After the duty ratios of every channel have been conﬁgured, the system will call

function pwm_start() to calculate timing cycle. Before that, parameters of all current

channels will be stored and protected by the system, calculation completion bits will

be cleared, too. When PWM period comes, parameters stored by the system will be

invoked.

•

When PWM period is discontinued new parameters will be applied, and ﬂags should

be set when the calculation of timing cycle is completed, so that cycles between

different colour shade with each new frame and simulate an intermediate shade,

achieving higher quality colour. The control of RGB colour lights is an good example

of PWM control.

•

The speciﬁc GPIO used can be conﬁgured in user_light.h. In our demo SDK, 5

channels of PWM is applied, however, it can be extended to 16 channels. Details on

how to extend the channels of PWM is explained in Chapter 3. The minimum

resolution can reach 45 ns at 1KHz refresh rate, while the minimum duty ratio can

reach 1/22222.

12.1.4. Parameter Speciﬁcation

•

Minimum resolution: 45 ns (approximately speaking, the PWM input clock frequency

is 22.72 MHz): >14 bit PWM @ 1 kHz

•

PWM period: 1000 μs (1 KHz) ~ 10000 μs (100 Hz)

12.2. Details on pwm.h

12.2.1. Sample Codes

#ifndef __PWM_H__

#define __PWM_H__

#define PWM_CHANNEL_NUM_MAX 8

//8 channels PWM at most

struct pwm_single_param {

//define the structure of a

single PWM parameter

uint16 gpio_set;

//GPIO needs to be set

uint16 gpio_clear;

//GPIO needs to be cleared

uint32 h_time;

//time needs to be written

into FRC1_LOAD

};

struct pwm_param {

//define the structure of

PWM parameter

Espressif

! /!

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2017.05

ESP8266 Datasheet(PDF) 98 Page - ESPRESSIF SYSTEMS (SHANGHAI) CO., LTD.

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