【IoT】ESP32 Arduino GPIO 使用簡析

一、GPIO 中斷使用簡析

1、中斷觸發方式

ESP32 Arduino 有以下四種觸發方式：

 LOW              低電平觸發
 CHANGE       電平變化
 RISING         上升沿觸發
 FALLING       下降沿觸發
 HIGH             高電平觸發

2、配置中斷

在定義中斷函數後，需要在 setup 函數配置中斷函數

// interrupt=中斷通道編號，function=中斷函數，mode=中斷觸發模式
attachInterrupt(interrupt, function, mode); 

// pin=中斷引腳，function=中斷函數，mode=中斷觸發模式
attachInterrupt(pin, function, mode);

如果在程序運行過程不需要使用外部中斷了，可以用中斷分離函數來取消這一中斷設置：

detachInterrupt(interrupt); 
detachInterrupt(Pin);。

3、示例

void setup()
{
  // 初始化日誌打印串口
  Serial.begin(115200);
  
  // 配置中斷引腳
  pinMode(26, INPUT|PULLUP );

  // 檢測到引腳 26 下降沿，觸發中斷函數 blink
  attachInterrupt(26, blink, FALLING);

  Serial.println("\nstart irq test");
}

void loop()
{

}

// 中斷函數
void blink()
{
  Serial.println("IRQ");
}

二、IIC 使用簡析

示例：

#include <Wire.h>

void setup() {
  // 啓動 i2c 總線
  Wire.begin();

  // 初始化串口
  Serial.begin(9600);
}

int reading = 0;

void loop() {
  // step 1: 啓動與從設備 #112 0x70 的數據交互
  Wire.beginTransmission(112);

  // 發送數據
  Wire.write(byte(0x00));
  Wire.write(byte(0x50));

  // 結束通信
  Wire.endTransmission();

  // step 2: 等待讀數據
  delay(70);

  // step 3: 讀取指定寄存器
  Wire.beginTransmission(112);
  Wire.write(byte(0x02));
  Wire.endTransmission();

  // step 4: 請求讀 2 字節數據
  Wire.requestFrom(112, 2);

  // step 5: 接收數據
  if (2 <= Wire.available()) {
    reading = Wire.read();
    reading = reading << 8;
    reading |= Wire.read();
    Serial.println(reading);
  }

  delay(250);
}

三、SPI 使用簡析

示例：

/* The ESP32 has four SPi buses, however as of right now only two of
 * them are available to use, HSPI and VSPI. Simply using the SPI API 
 * as illustrated in Arduino examples will use HSPI, leaving VSPI unused.
 * 
 * However if we simply intialise two instance of the SPI class for both
 * of these buses both can be used. However when just using these the Arduino
 * way only will actually be outputting at a time.
 * 
 * Logic analyser capture is in the same folder as this example as
 * "multiple_bus_output.png"
 * 
 * created 30/04/2018 by Alistair Symonds
 */
#include <SPI.h>

static const int spiClk = 1000000; // 1 MHz

//uninitalised pointers to SPI objects
SPIClass * vspi = NULL;
SPIClass * hspi = NULL;

void setup() {
  // 初始化 SPI 實例 VSPI、HSPI
  vspi = new SPIClass(VSPI);
  hspi = new SPIClass(HSPI);
  
  //clock miso mosi ss

  //使用默認 VSPI 引腳：SCLK = 18, MISO = 19, MOSI = 23, SS = 5
  vspi->begin();
  
  // alternatively route through GPIO pins of your choice
  //vspi->begin(0, 2, 4, 33); // SCLK, MISO, MOSI, SS
  
  //使用默認引腳初始化 HSPI
  //SCLK = 14, MISO = 12, MOSI = 13, SS = 15
  hspi->begin(); 

  //alternatively route through GPIO pins
  //hspi->begin(25, 26, 27, 32); //SCLK, MISO, MOSI, SS
  
  // 初始化 ss 片選引腳，默認爲低電平
  pinMode(5, OUTPUT); //VSPI SS
  pinMode(15, OUTPUT); //HSPI SS

}

// the loop function runs over and over again until power down or reset
void loop() {
  //use the SPI buses
  vspiCommand();
  hspiCommand();
  delay(100);
}

void vspiCommand() {
  // 模擬數據
  byte data = 0b01010101;

  // 啓動 VSPI 傳輸
  vspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
  digitalWrite(5, LOW);
  vspi->transfer(data);  
  digitalWrite(5, HIGH);
  vspi->endTransaction();
}

void hspiCommand() {
  byte stuff = 0b11001100;
  
  hspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
  digitalWrite(15, LOW);
  hspi->transfer(stuff);
  digitalWrite(15, HIGH);
  hspi->endTransaction();
}