板载资源的使用

本章主要是通过一些示例项目,阐述 BPI-Bit-S2 的外设的基本使用方法,通过下面的项目,您可以进行修改完成您的自己的项目。

上传代码时需要将 BPI-Bit-S2 开发板置于bootloader模式。

确保有一根type-c数据线,一端连接到PC,拿起开发板,保持上面无任何连线或外围硬件,按住Boot按钮,将type-c数据线与开发板连接,松开Boot按钮,在 Tools > Ports中选择新出现的端口。

点击 Upload 即可将代码编译并上传到开发板中。

项目一 WS2812

BPI-Bit-S2 使用25颗WS2812彩灯。 本项目是点亮 BPI-Bit-S2 的RGB彩灯的实验。

所需元件

BPI-Bit-S2 主板 X 1

注意:该项目不需要连接其他传感器。

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。 (这个程序需要Adafruit_NeoPixel库,需要在GitHub下载,解压到Arduino\ Library 文件夹下)代码如下:

展开查看

// NeoPixel Ring simple sketch (c) 2013 Shae Erisson
// Released under the GPLv3 license to match the rest of the
// Adafruit NeoPixel library

#include 
#ifdef __AVR__
 #include  // Required for 16 MHz Adafruit Trinket
#endif

// Which pin on the Arduino is connected to the NeoPixels?
#define PIN        18 // On Trinket or Gemma, suggest changing this to 1

// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS 25 // Popular NeoPixel ring size

// When setting up the NeoPixel library, we tell it how many pixels,
// and which pin to use to send signals. Note that for older NeoPixel
// strips you might need to change the third parameter -- see the
// strandtest example for more information on possible values.
Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

#define DELAYVAL 500 // Time (in milliseconds) to pause between pixels

void setup() {
  // These lines are specifically to support the Adafruit Trinket 5V 16 MHz.
  // Any other board, you can remove this part (but no harm leaving it):
#if defined(__AVR_ATtiny85__) && (F_CPU == 16000000)
  clock_prescale_set(clock_div_1);
#endif
  // END of Trinket-specific code.

  pixels.begin(); // INITIALIZE NeoPixel strip object (REQUIRED)
}

void loop() {
  pixels.clear(); // Set all pixel colors to 'off'

  // The first NeoPixel in a strand is #0, second is 1, all the way up
  // to the count of pixels minus one.
  for(int i=0; i < NUMPIXELS; i++) { // For each pixel...

    // pixels.Color() takes RGB values, from 0,0,0 up to 255,255,255
    // Here we're using a moderately bright green color:
    pixels.setPixelColor(i, pixels.Color(25, 25, 25));

    pixels.show();   // Send the updated pixel colors to the hardware.

    delay(DELAYVAL); // Pause before next pass through loop
  }
}

输入完成后,点击“编译”检查代码有无错误。确保没有错误后就可以开始上传了,点击“上传”之后 IDE 会把代码发送给 BPI-Bit-S2 主板。复位后WS2812灯会开始亮绿灯,

注意:如果需要其他颜色,可以修改代码中的RGB值。

代码分析

本项目使用 BPI-Bit-S2 集成的WS2812灯,默认GPIO是18。

#define PIN        18

设置GPIO引脚号

#define NUMPIXELS 25 

设置灯的个数,如果您想连接更多WS2812 彩灯,可以换一个IO,并修改灯的数量。

项目二 触摸传感器

BPI-Bit-S2 提供了多达 11 个可用的电容式传感器 GPIO,能够探测由手指或其他物品直接接触或接近而产生的电容差异。这种低噪声特性和电路的高灵敏度设计适用于较小的触摸板,可以直接用于触摸开关。本项目阐述了如何通过Arduino 代码获取 BPI-Bit-S2 的触摸传感器状态,并打印状态。

所需元件

BPI-Bit-S2 主板 X 1

注意:该项目不需要连接其他传感器。

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。

代码如下:

展开查看

 void setup() 
{ 
  Serial.begin(115200); 
      delay(1000); // give me time to bring up serial monitor 
      Serial.println("BPI-Bit-S2 Touch Test");    
}  
void loop(){ 
  Serial.println(touchRead(T2));  // get value using T0->D9  
  delay(100); 
} 

输入完成后,点击“编译”检查代码有无错误。确保没有错误后就可以开始上传了,点击“上传”之后 IDE 会把代码发送给 BPI-Bit-S2 主板。打开 Arduino IDE 串口监视器,并用手触摸 GPIO2(T2 对应的是GPIO2),可以看到会打印出的数据突然变小,如下图所示:

代码分析

获取触摸传感器的 GPIO 状态,只需要调用 touchRead 函数,函数原型如下:

 uint16_t touchRead(uint8_t pin)

返回“0”表示没有触摸,“1”表示触摸。其中 pin 是 T0~T9,对应到 BPI-Bit-S2的引脚如下表所示:

触摸传感器序号 对应的 ESP32 硬件 BPI-Bit-S2
T1 GPIO1 P1
T2 GPIO2 P2
T3 GPIO3 P3
T4 GPIO4 P4
T5 GPIO5 P5
T6 GPIO6 P6
T7 GPIO7 P7
T8 GPIO8 P8
T9 GPIO9 P9
T10 GPIO10 P10
T11 GPIO11 P11

项目三 串口实验

在最开始的章节中,我们上传了一个 Blink 闪烁程序来测试板子上的 LED 状态灯。现在,我们使用 UART 串口,每秒打印一次计时数据。

所需元件

BPI-Bit-S2 主板 X 1

硬件连接

此项目不需要其他传感器,所以只需要把BPI-Bit-S2用USB连到电脑就能用。

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。

代码如下:

展开查看

void setup() 
{
  Serial.begin(115200);         //设置串口通信波特率
} 
void loop() 
{
  static unsigned long i = 0;   //定义变量i
  Serial.println(i++);          //i加一后输出i
  delay(1000);                  //延时1秒
} 

输入完成后,点击“编译”检查代码有无错误。确保没有错误后就可以开始上传了,点击“上传”之后 IDE 会把代码发送给 BPI-Bit-S2 主板。上传完成之后,你需要按一下复位键,这样代码就能正常运行了

实验现象

完成之前步骤的上传后,打开 Arduino IDE 自带的串口监视器,可以看到如下的打印信息:

项目四 PWM(呼吸灯)

呼吸灯,即让 BPI-Bit-S2 通过 PWM 驱动 LED 灯,实现 LED 的亮度渐变,看起来就像是在呼吸一样。关于 PWM 的解释,请阅览知识扩展部分。

所需元件

BPI-Bit-S2 主板 X 1

LED X 1 (建议串联一个电阻限流)

硬件连接

将LED连接到BPI-Bit-S2的GPIO17就可以了,长的那个脚接GPIO17,短的接到GND

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。
代码如下:

展开查看

#define LED_CHANNEL_0     0    //设置通道0 
#define LED_TIMER_13_BIT  13   //设置13位定时器
#define LED_BASE_FREQ     5000 //设置定时器频率位5000Hz 
#define LED_PIN            13  //设置LED灯 

int brightness = 0;    // LED亮度
int fadeAmount = 1;    // LED数量

//设置led灯的亮度 
void ledcAnalogWrite(uint32_t value, uint32_t valueMax = 255) { 
  //计算占空比 
  uint32_t duty = (LED_BASE_FREQ / valueMax) * min(value, valueMax); 
  //设置占空比 
  ledcWrite(LED_CHANNEL_0, duty); 
}  
void setup() { 
  ledcSetup(LED_CHANNEL_0, LED_BASE_FREQ, LED_TIMER_13_BIT);   ledcAttachPin(LED_PIN, LED_CHANNEL_0); 
}  
void loop() { 
  ledcAnalogWrite(brightness);   brightness += fadeAmount; 

  if (brightness <= 0 || brightness >= 255) { 
       fadeAmount = -fadeAmount; 
  }   
  delay(30); 
}

输入完成后,点击“编译”按钮检查代码是否有错误。确定没有错误后可以开始上传了,点击“上传”按钮 。IDE 会把代码发送给 BPI-Bit-S2 主板。上传完成后您就可以看见Type-C旁边的LED 灯开始“呼吸”了!
现在让我们来回顾一下代码和硬件,看看它是如何工作。

知识学习

什么是 PWM 控制信号?

PWM(pulse-width modulation)脉冲宽度调制,MCU(微控制器)通过对开关器件的通断进行控制,使输出端得到一系列幅值相等的脉冲,用这些脉冲来代替正弦波或所需的波形。如下图所示:

其中,tON 是高电平持续时间,tPWM 是 PWM 波的周期,tPWM-tON 是低电平持续时间,占空比是指高电平持续时间占整个周期的比例,即 D=ton/tPWM 。

代码分析

BPI-Bit-S2 的 PWM 比普通的 Arduino UNO 高级的多,设置上不能简单的使用analogWrite 函数来驱动 PWM,而是需要设置 timer 函数,以及相关的频率参数等才能工作。

#define LEDC_CHANNEL_0     0

定义了定时器使用的通道,BPI-Bit-S2 总共有 16 个通道,这里用的是通道 0。

#define LEDC_TIMER_13_BIT  13

定义了定时器为 13 位定时器,即定时器最大计数为 2 的 13 次方。

#define LEDC_BASE_FREQ     5000

这是设置定时器的频率,单位是 Hz。接下来的 brightness 和 fadeAmount 参数分别表示 PWM 的占空比和每次变化的数值。

void ledcAnalogWrite(uint32_t value, uint32_t valueMax = 255)

这个函数是计算 PWM 占空比和设置 PWM 占空比,类似 Arduino 的 analogWrite 函数,可以看到,传递参数的最大值是 255,这是为了和 analogWrite 兼容。

ledcSetup(LEDC_CHANNEL_0, LEDC_BASE_FREQ, LEDC_TIMER_13_BIT); 
           ledcAttachPin(LED_PIN, LEDC_CHANNEL_0);

这两个函数是 BPI-Bit-S2 定时器设置函数,函数原型及原理这里不讲述,如果您感兴趣可以看看底层源码(源码地址:C:\Users\“your-PC”\AppData\Local\Arduino15\packages\esp32\ hardware\ adafruit_metro_esp32s2 \0.0.3\libraries\ESP32\),这里只需要知道怎么用这些函数来设置相关的 timer 就可以了。

关于什么是 PWM 信号,在前面已经阐述过了,这里不再说明。

注意:BPI-Bit-S2 的任何引脚都可以配置成 PWM 输出,您可以尝试着修改代码,完成您的项目。

项目五 ADC

ADC(模数转换器即 A/D 转换器),是指将模拟信号转变成数字信号。BPI-Bit-S2 的ADC 是13位的,最大输出值为 8191,而 Arduino UNO 是 10 位的,最大输出值是 1023,因此,在精度上比Arduino UNO 要高,而且转换速率快,且在使用上兼容 Arduino analogRead 函数,直接读取即可。

所需元件

模拟角度传感器 X 1

面包板 X 1

BPI-Bit-S2 主板 X 1

硬件连接

把 电位计插接到 BPI-Bit-S2 主板上,然后将模拟角度传感器插接到 IO2(实验中用的是IO2)。 元件连接好后,使用 USB 线连接 BPI-Bit-S2 和电脑。

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。代码如下:

展开查看

 void setup() { 
  // put your setup code here, to run once: 
  Serial.begin(115200); 
}  
void loop() { 
  // put your main code here, to run repeatedly:   
  Serial.println(analogRead(2));  
  delay(100); 
}

输入完成后,点击“编译”检查代码有无错误。确保没有错误后就可以开始上传了,点击“上传”之后IDE 会把代码发送给 BPI-Bit-S2 主板。上传完成后,打开 Arduino IDE 的串口监视器,旋转模拟角度传感器,可以看到串口监视器中的数值变化,如下图所示:

代码分析

由于BPI-Bit-S2 的 ADC 在使用上完全兼容 Arduino,因此这里不再对analogRead 函数进行过多的讲解。

注意:如果您对 Arduino 的基本函数不是特别熟悉,您可以点击链接进行学习。

项目六 I2C

BPI-Bit-S2 的 I2C 可以配置到任意 I/O 口,您可以通过传递相关参数进行配置。为了方便使用,我们已经将 I2C 进行了默认配置,在使用上完全兼容 Arduino,默认配置引脚可以在第一章简介中查看到。本项目是基于 I2C 默认配置,驱动 OLED 显示屏。

所需元件

I2C OLED-12864 显示屏 X 1

面包板 X 1

BPI-Bit-S2 主板 X 1

硬件连接

把BPI-Bit-S2 主板插到面包板上,然后将 OLED显示屏插接到 I2C 接口。(SDA是33,SCL是34)元件连接好后,使用 USB 线连接 BPI-Bit-S2 和电脑。

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。代码如下:

展开查看

#include  
   int UG2864Address = 0x3C;//OLED UG2864器件7位地址 

prog_char F8X16[][16] PROGMEM =
{
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,// 0
  0x00,0x00,0x00,0xF8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x33,0x30,0x00,0x00,0x00,//!1
  0x00,0x10,0x0C,0x06,0x10,0x0C,0x06,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//"2
  0x40,0xC0,0x78,0x40,0xC0,0x78,0x40,0x00,0x04,0x3F,0x04,0x04,0x3F,0x04,0x04,0x00,//#3
  0x00,0x70,0x88,0xFC,0x08,0x30,0x00,0x00,0x00,0x18,0x20,0xFF,0x21,0x1E,0x00,0x00,//$4
  0xF0,0x08,0xF0,0x00,0xE0,0x18,0x00,0x00,0x00,0x21,0x1C,0x03,0x1E,0x21,0x1E,0x00,//%5
  0x00,0xF0,0x08,0x88,0x70,0x00,0x00,0x00,0x1E,0x21,0x23,0x24,0x19,0x27,0x21,0x10,//&6
  0x10,0x16,0x0E,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//'7
  0x00,0x00,0x00,0xE0,0x18,0x04,0x02,0x00,0x00,0x00,0x00,0x07,0x18,0x20,0x40,0x00,//(8
  0x00,0x02,0x04,0x18,0xE0,0x00,0x00,0x00,0x00,0x40,0x20,0x18,0x07,0x00,0x00,0x00,//)9
  0x40,0x40,0x80,0xF0,0x80,0x40,0x40,0x00,0x02,0x02,0x01,0x0F,0x01,0x02,0x02,0x00,//*10
  0x00,0x00,0x00,0xF0,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x1F,0x01,0x01,0x01,0x00,//+11
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0xB0,0x70,0x00,0x00,0x00,0x00,0x00,//,12
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x01,0x01,0x01,0x01,0x01,0x01,//-13
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00,0x00,0x00,//.14
  0x00,0x00,0x00,0x00,0x80,0x60,0x18,0x04,0x00,0x60,0x18,0x06,0x01,0x00,0x00,0x00,///15
  0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x0F,0x10,0x20,0x20,0x10,0x0F,0x00,//016
  0x00,0x10,0x10,0xF8,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//117
  0x00,0x70,0x08,0x08,0x08,0x88,0x70,0x00,0x00,0x30,0x28,0x24,0x22,0x21,0x30,0x00,//218
  0x00,0x30,0x08,0x88,0x88,0x48,0x30,0x00,0x00,0x18,0x20,0x20,0x20,0x11,0x0E,0x00,//319
  0x00,0x00,0xC0,0x20,0x10,0xF8,0x00,0x00,0x00,0x07,0x04,0x24,0x24,0x3F,0x24,0x00,//420
  0x00,0xF8,0x08,0x88,0x88,0x08,0x08,0x00,0x00,0x19,0x21,0x20,0x20,0x11,0x0E,0x00,//521
  0x00,0xE0,0x10,0x88,0x88,0x18,0x00,0x00,0x00,0x0F,0x11,0x20,0x20,0x11,0x0E,0x00,//622
  0x00,0x38,0x08,0x08,0xC8,0x38,0x08,0x00,0x00,0x00,0x00,0x3F,0x00,0x00,0x00,0x00,//723
  0x00,0x70,0x88,0x08,0x08,0x88,0x70,0x00,0x00,0x1C,0x22,0x21,0x21,0x22,0x1C,0x00,//824
  0x00,0xE0,0x10,0x08,0x08,0x10,0xE0,0x00,0x00,0x00,0x31,0x22,0x22,0x11,0x0F,0x00,//925
  0x00,0x00,0x00,0xC0,0xC0,0x00,0x00,0x00,0x00,0x00,0x00,0x30,0x30,0x00,0x00,0x00,//:26
  0x00,0x00,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x60,0x00,0x00,0x00,0x00,//;27
  0x00,0x00,0x80,0x40,0x20,0x10,0x08,0x00,0x00,0x01,0x02,0x04,0x08,0x10,0x20,0x00,//<28
  0x40,0x40,0x40,0x40,0x40,0x40,0x40,0x00,0x04,0x04,0x04,0x04,0x04,0x04,0x04,0x00,//=29
  0x00,0x08,0x10,0x20,0x40,0x80,0x00,0x00,0x00,0x20,0x10,0x08,0x04,0x02,0x01,0x00,//>30
  0x00,0x70,0x48,0x08,0x08,0x08,0xF0,0x00,0x00,0x00,0x00,0x30,0x36,0x01,0x00,0x00,//?31
  0xC0,0x30,0xC8,0x28,0xE8,0x10,0xE0,0x00,0x07,0x18,0x27,0x24,0x23,0x14,0x0B,0x00,//@32
  0x00,0x00,0xC0,0x38,0xE0,0x00,0x00,0x00,0x20,0x3C,0x23,0x02,0x02,0x27,0x38,0x20,//A33
  0x08,0xF8,0x88,0x88,0x88,0x70,0x00,0x00,0x20,0x3F,0x20,0x20,0x20,0x11,0x0E,0x00,//B34
  0xC0,0x30,0x08,0x08,0x08,0x08,0x38,0x00,0x07,0x18,0x20,0x20,0x20,0x10,0x08,0x00,//C35
  0x08,0xF8,0x08,0x08,0x08,0x10,0xE0,0x00,0x20,0x3F,0x20,0x20,0x20,0x10,0x0F,0x00,//D36
  0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,0x20,0x3F,0x20,0x20,0x23,0x20,0x18,0x00,//E37
  0x08,0xF8,0x88,0x88,0xE8,0x08,0x10,0x00,0x20,0x3F,0x20,0x00,0x03,0x00,0x00,0x00,//F38
  0xC0,0x30,0x08,0x08,0x08,0x38,0x00,0x00,0x07,0x18,0x20,0x20,0x22,0x1E,0x02,0x00,//G39
  0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,0x20,0x3F,0x21,0x01,0x01,0x21,0x3F,0x20,//H40
  0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//I41
  0x00,0x00,0x08,0x08,0xF8,0x08,0x08,0x00,0xC0,0x80,0x80,0x80,0x7F,0x00,0x00,0x00,//J42
  0x08,0xF8,0x88,0xC0,0x28,0x18,0x08,0x00,0x20,0x3F,0x20,0x01,0x26,0x38,0x20,0x00,//K43
  0x08,0xF8,0x08,0x00,0x00,0x00,0x00,0x00,0x20,0x3F,0x20,0x20,0x20,0x20,0x30,0x00,//L44
  0x08,0xF8,0xF8,0x00,0xF8,0xF8,0x08,0x00,0x20,0x3F,0x00,0x3F,0x00,0x3F,0x20,0x00,//M45
  0x08,0xF8,0x30,0xC0,0x00,0x08,0xF8,0x08,0x20,0x3F,0x20,0x00,0x07,0x18,0x3F,0x00,//N46
  0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,0x0F,0x10,0x20,0x20,0x20,0x10,0x0F,0x00,//O47
  0x08,0xF8,0x08,0x08,0x08,0x08,0xF0,0x00,0x20,0x3F,0x21,0x01,0x01,0x01,0x00,0x00,//P48
  0xE0,0x10,0x08,0x08,0x08,0x10,0xE0,0x00,0x0F,0x18,0x24,0x24,0x38,0x50,0x4F,0x00,//Q49
  0x08,0xF8,0x88,0x88,0x88,0x88,0x70,0x00,0x20,0x3F,0x20,0x00,0x03,0x0C,0x30,0x20,//R50
  0x00,0x70,0x88,0x08,0x08,0x08,0x38,0x00,0x00,0x38,0x20,0x21,0x21,0x22,0x1C,0x00,//S51
  0x18,0x08,0x08,0xF8,0x08,0x08,0x18,0x00,0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00,//T52
  0x08,0xF8,0x08,0x00,0x00,0x08,0xF8,0x08,0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00,//U53
  0x08,0x78,0x88,0x00,0x00,0xC8,0x38,0x08,0x00,0x00,0x07,0x38,0x0E,0x01,0x00,0x00,//V54
  0xF8,0x08,0x00,0xF8,0x00,0x08,0xF8,0x00,0x03,0x3C,0x07,0x00,0x07,0x3C,0x03,0x00,//W55
  0x08,0x18,0x68,0x80,0x80,0x68,0x18,0x08,0x20,0x30,0x2C,0x03,0x03,0x2C,0x30,0x20,//X56
  0x08,0x38,0xC8,0x00,0xC8,0x38,0x08,0x00,0x00,0x00,0x20,0x3F,0x20,0x00,0x00,0x00,//Y57
  0x10,0x08,0x08,0x08,0xC8,0x38,0x08,0x00,0x20,0x38,0x26,0x21,0x20,0x20,0x18,0x00,//Z58
  0x00,0x00,0x00,0xFE,0x02,0x02,0x02,0x00,0x00,0x00,0x00,0x7F,0x40,0x40,0x40,0x00,//[59
  0x00,0x0C,0x30,0xC0,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x06,0x38,0xC0,0x00,//\60
  0x00,0x02,0x02,0x02,0xFE,0x00,0x00,0x00,0x00,0x40,0x40,0x40,0x7F,0x00,0x00,0x00,//]61
  0x00,0x00,0x04,0x02,0x02,0x02,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//^62
  0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x80,//_63
  0x00,0x02,0x02,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//`64
  0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x19,0x24,0x22,0x22,0x22,0x3F,0x20,//a65
  0x08,0xF8,0x00,0x80,0x80,0x00,0x00,0x00,0x00,0x3F,0x11,0x20,0x20,0x11,0x0E,0x00,//b66
  0x00,0x00,0x00,0x80,0x80,0x80,0x00,0x00,0x00,0x0E,0x11,0x20,0x20,0x20,0x11,0x00,//c67
  0x00,0x00,0x00,0x80,0x80,0x88,0xF8,0x00,0x00,0x0E,0x11,0x20,0x20,0x10,0x3F,0x20,//d68
  0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x1F,0x22,0x22,0x22,0x22,0x13,0x00,//e69
  0x00,0x80,0x80,0xF0,0x88,0x88,0x88,0x18,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//f70
  0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x6B,0x94,0x94,0x94,0x93,0x60,0x00,//g71
  0x08,0xF8,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20,//h72
  0x00,0x80,0x98,0x98,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//i73
  0x00,0x00,0x00,0x80,0x98,0x98,0x00,0x00,0x00,0xC0,0x80,0x80,0x80,0x7F,0x00,0x00,//j74
  0x08,0xF8,0x00,0x00,0x80,0x80,0x80,0x00,0x20,0x3F,0x24,0x02,0x2D,0x30,0x20,0x00,//k75
  0x00,0x08,0x08,0xF8,0x00,0x00,0x00,0x00,0x00,0x20,0x20,0x3F,0x20,0x20,0x00,0x00,//l76
  0x80,0x80,0x80,0x80,0x80,0x80,0x80,0x00,0x20,0x3F,0x20,0x00,0x3F,0x20,0x00,0x3F,//m77
  0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x3F,0x21,0x00,0x00,0x20,0x3F,0x20,//n78
  0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x00,0x1F,0x20,0x20,0x20,0x20,0x1F,0x00,//o79
  0x80,0x80,0x00,0x80,0x80,0x00,0x00,0x00,0x80,0xFF,0xA1,0x20,0x20,0x11,0x0E,0x00,//p80
  0x00,0x00,0x00,0x80,0x80,0x80,0x80,0x00,0x00,0x0E,0x11,0x20,0x20,0xA0,0xFF,0x80,//q81
  0x80,0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x20,0x20,0x3F,0x21,0x20,0x00,0x01,0x00,//r82
  0x00,0x00,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x33,0x24,0x24,0x24,0x24,0x19,0x00,//s83
  0x00,0x80,0x80,0xE0,0x80,0x80,0x00,0x00,0x00,0x00,0x00,0x1F,0x20,0x20,0x00,0x00,//t84
  0x80,0x80,0x00,0x00,0x00,0x80,0x80,0x00,0x00,0x1F,0x20,0x20,0x20,0x10,0x3F,0x20,//u85
  0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,0x00,0x01,0x0E,0x30,0x08,0x06,0x01,0x00,//v86
  0x80,0x80,0x00,0x80,0x00,0x80,0x80,0x80,0x0F,0x30,0x0C,0x03,0x0C,0x30,0x0F,0x00,//w87
  0x00,0x80,0x80,0x00,0x80,0x80,0x80,0x00,0x00,0x20,0x31,0x2E,0x0E,0x31,0x20,0x00,//x88
  0x80,0x80,0x80,0x00,0x00,0x80,0x80,0x80,0x80,0x81,0x8E,0x70,0x18,0x06,0x01,0x00,//y89
  0x00,0x80,0x80,0x80,0x80,0x80,0x80,0x00,0x00,0x21,0x30,0x2C,0x22,0x21,0x30,0x00,//z90
  0x00,0x00,0x00,0x00,0x80,0x7C,0x02,0x02,0x00,0x00,0x00,0x00,0x00,0x3F,0x40,0x40,//{91
  0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xFF,0x00,0x00,0x00,//|92
  0x00,0x02,0x02,0x7C,0x80,0x00,0x00,0x00,0x00,0x40,0x40,0x3F,0x00,0x00,0x00,0x00,//}93
  0x00,0x06,0x01,0x01,0x02,0x02,0x04,0x04,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,//~94
};


char ch_buf[17]={0};
int RES = 6;//Gadgeteer PIN6
int DC = 7;//Gadgeteer PIN3

void Writec(unsigned char COM)
{
  Wire.beginTransmission(UG2864Address);
  Wire.write(0x00);
  Wire.write(COM);
  Wire.endTransmission();
}

void Writed(unsigned char DATA)
{
  Wire.beginTransmission(UG2864Address);
  Wire.write(0x40);
  Wire.write(DATA);
  Wire.endTransmission();
}

void SSD1306()
{
  Writec(0XAE);//display off
  Writec(0X00);//set lower column address
  Writec(0X10);//set higher column address
  Writec(0X40);//set display start line
  Writec(0XB0);//set page address
  Writec(0X81);//set contract control
  Writec(0XCF);// VCC Generated by Internal DC/DC Circuit
  Writec(0XA0);//set segment remap  column address 127 is mapped to SEG0
  Writec(0XA6);//normal / reverse   normal display
  Writec(0XA8);//multiplex ratio
  Writec(0X3F);//1/64
  Writec(0XC0);//Com scan direction remapped mode. Scan from COM[N-1] to COM0
  Writec(0XD3);//set display offset
  Writec(0X00);
  Writec(0XD5);//set osc division
  Writec(0X80);
  Writec(0XD9);//set pre-charge period
  Writec(0X11);
  Writec(0XDa);//set COM pins
  Writec(0X12);
  Writec(0X8d);/*set charge pump enable*/
  Writec(0X14);
  Writec(0Xdb);//Set VcomH
  Writec(0X20);
  Writec(0XAF);//display ON
}
void fill(unsigned char dat)
{
  unsigned char i,j;

  Writec(0x00);//set lower column address
  Writec(0x10);//set higher column address
  Writec(0xB0);//set page address

  for(j=0;j<8;j++)
  {
    Writec(0xB0+j);//set page address
    Writec(0x00);//set lower column address
    Writec(0x10);//set higher column address
    for(i=0;i<128;i++)
    {
      Writed(dat);
    }
  }
}

void show_string(unsigned char x,unsigned char y,char *s)
{
  unsigned char i,j,lower,higher;
  char *t;
  t=s;
  lower=y%16;
  higher=y/16;
  if((x>3) || (y>120))
    return;
  Writec(0xB0+x*2);//set page address
  Writec(lower);//set lower column address
  Writec(0x10+higher);//set higher column address
  for(j=0;*s!='\0';j++)
  {

    for(i=0;i<8;i++){
      ch_buf[i] = pgm_read_word(&F8X16[*s-32][i]);
    }
    for(i=0;i<8;i++)
      Writed(ch_buf[i]);
    s++;
  }
  Writec(0xB0+x*2+1);//set page address
  Writec(lower);//set lower column address
  Writec(0x10+higher);//set higher column address
  s=t;
  for(j=0;*s!='\0';j++)
  {
    for(i=0;i<8;i++){
      ch_buf[i] = pgm_read_word(&F8X16[*s-32][i+8]);
    }
    for(i=0;i<8;i++)
      Writed(ch_buf[i]);
    s++;
  }
}



void oled_init(void)
{
  pinMode(RES,OUTPUT);//RES
  pinMode(DC,OUTPUT);//D/C#

  digitalWrite(DC,LOW);
  Wire.begin();
  digitalWrite(RES,HIGH);   delay(100);
  digitalWrite(RES,LOW);    delay(100);
  digitalWrite(RES,HIGH);   delay(100);
  SSD1306();
  fill(0x00);
}

void setup() {
  oled_init();
}


void loop()
{
      fill(0x00);
      show_string(0,12,"BananaPi");

      show_string(2,12,"banana-pi.org");
      while(1);
}


输入完成后,点击“编译”检查代码有无错误。确保没有错误后就可以开始上传了,点击“上传”之后 IDE 会把代码发送给 BPI-Bit-S2 主板。上传完成后,OLED 显示屏会显示“BananaPi banana-pi.org”字样。

代码分析

本项目的代码相对于前面的项目较多,主要是基于 I2C 通信对 OLED 显示屏底层寄存器的直接驱动。

void Writec(unsigned char COM)

设置寄存器函数,通过 I2C 对 OLED 显示屏设置,I2C 使用方法完全兼容 Arduino。

void Writed(unsigned char DATA)

写数据函数,I2C 使用方法完全兼容 Arduino。

注意:BPI-Bit-S2 的 I2C 与 Arduino 完全兼容,主要是调用 Wire 库文件使用。

项目七 SPI

在很多传感器中,都使用 SPI 通信,因为 SPI 通信速率相对于 I2C 更快,没有地址冲突的弊端。SPI,是 一种高速的、全双工、同步的通信总线,而 BPI-Bit-S2 的 SPI 可以配置到所有 I/O,您可以阅览底层 代码进行使用(初学者不建议使用)。为了更好的使用体验,BPI-Bit-S2 默认情况下配置了IO35、IO36、IO37 为 SPI 口,在使用上则完全兼容 Arduino。 本项目使用 BPI-Bit-S2,通过 SPI 读取 BME280 温湿度传感器的数据,示例中使用的是BME280 库文件,关于 SPI 驱动您可以阅览 BEM280 库文件,点击链接下载 BME280 库文件。

所需元件

BME280 温湿度传感器 X 1

注意:BME280 传感器本身支持 I2C 和 SPI 通信,这里我们采用 SPI 通信。

面包板 X 1

BPI-Bit-S2 主板 X 1

输入代码

打开 Arduino IDE。尽管可以直接复制代码,我们还是建议您自己手动输入代码熟悉下。 (这个程序需要DFRobot_BME280库,需要在GitHub下载,解压到Arduino\ Library 文件夹下 )代码如下:

展开查看

/*!
 * read_data_spi.ino
 *
 * Download this demo to test read data from bme280, connect sensor through spi interface
 * Connect cs pin to io 2
 * Data will print on your serial monitor
 *
 * Copyright   [DFRobot](http://www.dfrobot.com), 2016
 * Copyright   GNU Lesser General Public License
 *
 * version  V1.0
 * date  12/03/2019
 */

#include "DFRobot_BME280.h"
#include "Wire.h"

typedef DFRobot_BME280_SPI    BME;    // ******** use abbreviations instead of full names ********

# define PIN_CS   2

BME   bme(&SPI, PIN_CS);   // select TwoWire peripheral and set cs pin id

#define SEA_LEVEL_PRESSURE    1015.0f

// show last sensor operate status
void printLastOperateStatus(BME::eStatus_t eStatus)
{
  switch(eStatus) {
  case BME::eStatusOK:    Serial.println("everything ok"); break;
  case BME::eStatusErr:   Serial.println("unknow error"); break;
  case BME::eStatusErrDeviceNotDetected:    Serial.println("device not detected"); break;
  case BME::eStatusErrParameter:    Serial.println("parameter error"); break;
  default: Serial.println("unknow status"); break;
  }
}

void setup()
{
  Serial.begin(115200);
  bme.reset();
  Serial.println("bme read data test");
  while(bme.begin() != BME::eStatusOK) {
    Serial.println("bme begin faild");
    printLastOperateStatus(bme.lastOperateStatus);
    delay(2000);
  }
  Serial.println("bme begin success");
  delay(100);
}

void loop()
{
  float   temp = bme.getTemperature();
  uint32_t    press = bme.getPressure();
  float   alti = bme.calAltitude(SEA_LEVEL_PRESSURE, press);
  float   humi = bme.getHumidity();

  Serial.println();
  Serial.println("======== start print ========");
  Serial.print("temperature (unit Celsius): "); Serial.println(temp);
  Serial.print("pressure (unit pa):         "); Serial.println(press);
  Serial.print("altitude (unit meter):      "); Serial.println(alti);
  Serial.print("humidity (unit percent):    "); Serial.println(humi);
  Serial.println("========  end print  ========");

  delay(1000);
}


输入完成后,点击“编译”检查代码有无错误。确保没有错误后就可以开始上传了,点击“上传”之后 IDE 会把代码发送给 BPI-Bit-S2 主板。打开 Arduino 串口监视器,可以看到打印信息如下:

代码分析

本项目采用的是 BME280 库文件,在 Item-5.ino 文件中并没有对 SPI 底层进行操作,不过,BPI-Bit-S2 ESP32-S3 的 SPI 使用完全兼容 Arduino。