User's Manual

Several SPI modes can be supported, including Standard SPI, Dual SPI, and Quad SPI.
Therefore, please choose the correct SPI mode when you are downloading into the fl ash, otherwise
firmwares/programs that you downloaded may not work in the right way.
3.3. Crystal
Currently, the frequency of crystal oscillators supported include 40MHz, 26MHz and 24MHz. The accuracy
of crystal oscillators applied should be ±10PPM, and the operating temperature range should be between
-20°C and 85°C.
When using the downloading tools, please remember to select the right crystal oscillator type. In circuit design,
capacitors C1 and C2, which are connected to the earth, are added to the input and output terminals of the
crystal oscillator respectively. The values of the two capacitors can be flexible, ranging from 6pF to 22pF,
however, the specific capacitive values of C1 and C2 depend on further testing and adjustment on the overall
performance of the whole circuit. Normally, the capacitive values of C1 and C2 are within 10pF if the crystal
oscillator frequency is 26MHz, while the values of C1 and C2 are 10pF<C1, C2<22pF if the crystal oscillator
frequency is 40MHz.
3.4. Interfaces
Table 7 Descriptions of Interfaces
Interface Pin Name Description
HSPI
IO12(MISO)
IO13(MOSI)
IO14(CLK)
IO15(CS)
SPI Flash 2, display screen, and MCU can be connected using HSPI interface.
PWM
IO12(R)
IO15(G)
IO13(B)
Currently the PWM interface has four channels, but users can extend the
channels according to their own needs. PWM interface can be used to control
LED lights, buzzers, relays, electronic machines, and so on.
IR Remote
Control
IO14(IR_T)
IO5(IR_R)
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 38KHz.
ADC TOUT
ESP8266EX integrates a 10-bit analog ADC. It can be used to test the
power-supply voltage of VDD3P3 (Pin3 and Pin4) and the input power voltage
of TOUT (Pin 6). However, these two functions cannot be used
simultaneously. This interface is typically used in sensor products.
I2C
IO14(SCL)
IO2(SDA)
I2C interface can be used to connect external sensor products and display
screens, etc.