a. With the standard font, what is the longest message you can write across one line of the display? How many lines can you write?
14 characters message in 6 lines.
a. Include the code that you had to insert to do this in your lab writeup.
#include <SPI.h>
#include <SD.h>
const int chipSelect = 17;
void setup()
{
// Open serial communications and wait for port to open:
Serial.begin(9600);
delay(1000);
}
Serial.print("Initializing SD card...");
pinMode(17, OUTPUT); //set SS pin as output.
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
Serial.println("Card failed, or not present");
// don't do anything more:
return;
}
Serial.println("card initialized.");
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
File dataFile = SD.open("datalog.txt", FILE_WRITE);
// if the file is available, write to it:
if (dataFile) {
dataFile.println("You shall not pass!");
dataFile.close();
Serial.println("The file has been modified");
}
// if the file isn't open, pop up an error:
else {
Serial.println("error opening datalog.txt");
}
dataFile = SD.open("datalog.txt");
if (dataFile)
{
Serial.println("Modified File: ");
while(dataFile.available())
{
Serial.write(dataFile.read());
}
dataFile.close();
}
else
Serial.println("error opening datalog.txt");
}
void loop()
{
}
b. Explain what would you do differently (or show us your code!) to insert the same text string, but at the beginning of the file (without over-writing the current contents).
use seek and position functions
