ESP8266 datasheet(12/117 Pages) ESPRESSIF

12 / 117 page

1. Overview

1.7. Pulse-Width Modulation (PWM)

ESP8266EX has four PWM output interfaces. They can be extended by users themselves.

The pin deﬁnitions of the PWM interfaces are deﬁned as below.

The functionality of PWM interfaces can be implemented via software programming. For

example, in the LED smart light demo, the function of PWM is realized by interruption of the

timer, the minimum resolution reaches as much as 44 ns. PWM frequency range is

adjustable from 1000 μs to 10000 μs, i.e., between 100Hz and 1 kHz. When the PWM

frequency is 1 kHz, the duty ratio will be 1/22727, and over 14 bit resolution will be

achieved at 1 kHz refresh rate.

1.8. IR Remote Control

One Infrared remote control interface is deﬁned as below.

The functionality of Infrared remote control interface can be implemented via software

programming. NEC coding, modulation, and demodulation are used by this interface. The

frequency of modulated carrier signal is 38 kHz, while the duty ratio of the square wave is

1/3. The transmission range is around 1m which is determined by two factors: one is the

maximum value of rated current, the other is internal current-limiting resistance value in the

infrared receiver. The larger the resistance value, the lower the current, so is the power, and

vice versa. The transmission angle is between 15° and 30° which is determined by the

radiation direction of the infrared receiver.

! Note:

By default, UART0 outputs some printed information when the device is powered on and booting up. The

baud rate of the printed information is relevant to the frequency of the external crystal oscillator. If the

frequency of the crystal oscillator is 40 MHz, then the baud rate for printing is 115200; if the frequency of the

crystal oscillator is 26 MHz, then the baud rate for printing is 74880. If the printed information exerts any

inﬂuence on the functionality of the device, it is suggested to block the printing during the power-on period by

changing (U0TXD,U0RXD) to (MTDO,MTCK).

Table 1-7. Pin Deﬁnitions of PWM

Pin Name

Pin Num

Function Name

MTDI

IO12

PWM0

MTDO

IO15

PWM1

MTMS

IO14

PWM2

GPIO4

IO4

PWM3

Table 1-8. Pin Deﬁnitions of IR Remote Control

Pin Name

Pin Num

Function Name

MTMS

IO14

IR Tx

GPIO5

IO5

IR Rx

Espressif

! /104

2017.05

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