Wio Terminal 采集模拟数据

Demo 概述

这个 Demo 的功能是在 Wio Terminal 上以折线图的方式实时显示光线传感器(Light Sensor)的数据。Wio Terminal 内置了一个光线传感器,因此你不需要额外准备外设模块。除了在 LCD 上实时显示,我们还将传感器数据输出到串口,打开 Arduino IDE 的串口绘图器(Serial Plotter)同样可以看到折线图。另外,为了更进一步,我们还将光线传感器的数据存储到 SD 卡中,在一个名为 Readings.txt 的文件。

重点难点

  • 如何将光线传感器数据显示在 LCD 折线图中;
  • 如何将光线传感器数据存储到 SD 卡中。

安装依赖库

本示例 Demo 依赖 LCD 库、 Linechart 库和 FS 库:

功能实现

初始化 LCD 和 I/O 引脚

Wio Terminal 内置光线传感器的引脚定义是 WIO_LIGHT,初始化代码如下。(可参考 Wio Terminal 光线传感器Wio Terminal 文件系统

#include <SPI.h>
#include <Seeed_FS.h>
#include "SD/Seeed_SD.h"
#include"seeed_line_chart.h" //include the library

File myFile;
TFT_eSPI tft;
TFT_eSprite spr = TFT_eSprite(&tft);  // Sprite 

#define max_size 30 //maximum size of data
doubles data; //Initilising a doubles type to store data
int brightness;

void setup() {
    Serial.begin(115200);
    if (!SD.begin(SDCARD_SS_PIN, SDCARD_SPI)) {
        Serial.println("initialization failed!");
        while(1);
    }
    pinMode(WIO_LIGHT, INPUT);
    tft.begin();
    tft.setRotation(3);
    spr.createSprite(TFT_HEIGHT,TFT_WIDTH);
}

读取光线传感器数据并存储到 SD 卡

void loop() {
    spr.fillSprite(TFT_WHITE);
    brightness = analogRead(WIO_LIGHT); //Reading light sensor values

    if (data.size() == max_size) {
        data.pop();//this is used to remove the first read variable
    }
    data.push(brightness); //Storing light sensor values
    saveData(); //Saving data to SD card
    ...
}

设置折线图标题(至于为什么这样设置,请参考 Wio Terminal LCD 折线图

//Settings for the line graph title
auto header =  text(0, 0)
            .value("Light Sensor Readings")
            .align(center)
            .valign(vcenter)
            .width(tft.width())
            .thickness(2);

header.height(header.font_height() * 2);
header.draw(); //Header height is the twice the height of the font

配置折线图数据

//Settings for the line graph
auto content = line_chart(20, header.height()); //(x,y) where the line graph begins
        content
            .height(tft.height() - header.height() * 1.5) //actual height of the line chart
            .width(tft.width() - content.x() * 2) //actual width of the line chart
            .based_on(0.0) //Starting point of y-axis, must be a float
            .show_circle(false) //drawing a cirle at each point, default is on.
            .value(data) //passing through the data to line graph
            .color(TFT_RED) //Setting the color for the line
            .draw();

spr.pushSprite(0, 0);

将数据写到 SD 卡(具体说明可参考 Wio Terminal 文件系统

void saveData(){
     myFile = SD.open("Readings.txt",FILE_APPEND);
     brightness = analogRead(WIO_LIGHT);
     Serial.println(brightness);
     myFile.println(brightness);
     myFile.close();
}

完整代码

#include <SPI.h>
#include <Seeed_FS.h>
#include "SD/Seeed_SD.h"
#include"seeed_line_chart.h" //include the library

File myFile;
TFT_eSPI tft;
TFT_eSprite spr = TFT_eSprite(&tft);  // Sprite 

#define max_size 30 //maximum size of data
doubles data; //Initilising a doubles type to store data
int brightness;

void setup() {
    Serial.begin(115200);
    if (!SD.begin(SDCARD_SS_PIN, SDCARD_SPI)) {
        Serial.println("initialization failed!");
        while(1);
    }
    pinMode(WIO_LIGHT, INPUT);
    tft.begin();
    tft.setRotation(3);
    spr.createSprite(TFT_HEIGHT,TFT_WIDTH);
}

void loop() {
    spr.fillSprite(TFT_WHITE);
    brightness = analogRead(WIO_LIGHT);

    if (data.size() == max_size) {
        data.pop();//this is used to remove the first read variable
    }
    data.push(brightness); //read variables and store in data
    saveData();

    //Settings for the line graph title
    auto header =  text(0, 0)
                .value("Light Sensor Readings")
                .align(center)
                .valign(vcenter)
                .width(tft.width())
                .thickness(2);

    header.height(header.font_height() * 2);
    header.draw(); //Header height is the twice the height of the font

  //Settings for the line graph
    auto content = line_chart(20, header.height()); //(x,y) where the line graph begins
         content
                .height(tft.height() - header.height() * 1.5) //actual height of the line chart
                .width(tft.width() - content.x() * 2) //actual width of the line chart
                .based_on(0.0) //Starting point of y-axis, must be a float
                .show_circle(false) //drawing a cirle at each point, default is on.
                .value(data) //passing through the data to line graph
                .color(TFT_RED) //Setting the color for the line
                .draw();

    spr.pushSprite(0, 0);
}

void saveData(){
     myFile = SD.open("Readings.txt",FILE_APPEND);
     brightness = analogRead(WIO_LIGHT);
     Serial.println(brightness);
     myFile.println(brightness);
     myFile.close();
}

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