ESP8266 datasheet(97/117 Pages) ESPRESSIF

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12. PWM Interface

12.

PWM Interface

12.1. Functional Overview

12.1.1. Features

PWM (Pulse Width Modulation) can be implemented on Frame Rate Control 1 (FRC1) via

software programming, achieving multi-channelled PWM with the same frequency but

different duty ratio. It can be used to control devices such as color lights, buzzer, and

electric machines, etc.

Features of PWM are listed below:

• Apply NMI (Non Maskable Interrupt) to interrupt, more precise.

• Can be extended to 8 channels of PWM signal.

• Resolution ratio higher than 14 bit, the minimum resolution can reach 45 ns.

• Conﬁguration can be completed by call interface functions, without set the register.

12.1.2. Implementation

An optimized software algorithm provided by ESP8266 system enable the transmission of

multi-channel PWM signals via GPIO (General Purpose Input Output) interface by way of

mounting NMI on FRC1 timer.

The clock of PWM is provided by high-speed system clock, the frequency speed of which

can reach as high as 80MHz. Through pre-frequency divider, the clock source can be

divided into 16 separated frequencies, the input clock frequency of which is 5MHz. PWM

can issue coarse tuning timing via FRC1, which combined with ﬁne tuning issued by the

high-speed system clock, can improve the resolution to as much as 45 ns.

! Note:

FRC1 is a 23-bit hardware timer.

⚠ Notice:

•

PWM can not be used when APIs in hw_timer.c are in use, because they all use the same hardware

timer.

•

Do not set the system to be Light Sleep mode (Do not call

wifi_set_sleep_type(LIGT_SLEEP);, because that Light Sleep will stop the CPU, it can not

be interrupted by NMI during light sleep.

•

To enter Deep Sleep mode, PWM needs to be stopped ﬁrst.

! Note:

The highest priority level of interrupt owned by NMI ensures the precision of PWM output waveform.

Espressif

! /!

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2017.05

ESP8266 Datasheet(PDF) 97 Page - ESPRESSIF SYSTEMS (SHANGHAI) CO., LTD.