之前文章中写到Arduino的TF卡扩展,要做这个是因为一个项目要用TF卡存储信息,把收集到的数据存在一个txt文件里,之前提到CardInfo程序工作正常,输出了TF卡的相关信息,那么接下来,就继续完成创建并读写TXT文件的操作。
在IDE的例程中,有一个名为ReadWrite的例程,这个例程即可完成上述功能。
下面是程序源码:
#include <SPI.h>
#include <SD.h>
File myFile;
void setup() {
// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.print("Initializing SD card...");
if (!SD.begin(4)) {
Serial.println("initialization failed!");
return;
}
Serial.println("initialization done.");
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
myFile = SD.open("test.txt", FILE_WRITE);
// if the file opened okay, write to it:
if (myFile) {
Serial.print("Writing to test.txt...");
myFile.println("testing 1, 2, 3.");
// close the file:
myFile.close();
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
// re-open the file for reading:
myFile = SD.open("test.txt");
if (myFile) {
Serial.println("test.txt:");
// read from the file until there's nothing else in it:
while (myFile.available()) {
Serial.write(myFile.read());
}
// close the file:
myFile.close();
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
}
void loop() {
// nothing happens after setup
}
源码解析:
首先,程序在Setup中就已经完成,loop中为空。
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
随后,进行SD卡的初始化。
if (!SD.begin(4)) {//片选管脚初始化为4,若初始化失败,则返回值为0,输出initialization failed!
Serial.println("initialization failed!");
return;
}
之后,我们打开名为TEXT.txt的文件,注意,如果SD卡中没有改文件则程序会自动创建。
myFile = SD.open("test.txt", FILE_WRITE);
如果文件打开成功,向文件中写入testing 1, 2, 3.
if (myFile) {
Serial.print("Writing to test.txt...");
myFile.println("testing 1, 2, 3.");
// close the file:
myFile.close();
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
写入完成后,文件关闭。再打开我们刚刚打开的txt文件,验证是否写入。
while (myFile.available()) {
Serial.write(myFile.read());//不停读取文件,并直接写到串口
}
结果如下:
Initializing SD card...initialization done.
Writing to test.txt...done.
test.txt:
testing 1, 2, 3.
如果之前运行CardInfo程序没有问题,ReadWrite程序应当也能运行成功。