Pulse-Width Modulation (Pwm); Ir Remote Control - Espressif ESP8266 Technical Reference

!
! 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).

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.
MTDI
MTDO
MTMS
GPIO4
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.
MTMS
GPIO5
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.
Espressif
Pin Name Pin Num
10
13
9
16
Table 1-8. Pin Definitions of IR Remote Control
Pin Name Pin Num
9
24
Table 1-7. Pin Definitions of PWM
IO
IO12
IO15
IO14
IO4
IO
IO14
IO5
4 ! /86
1. Overview
Function Name
PWM0
PWM1
PWM2
PWM3
Function Name
IR Tx
IR Rx
2016.05