hai I am new to Arduino programming I want to use read() and available() functions in my code but I am facing some problems
1:-unable to get return value when used available() function
2:-unable to read characters properly when used read() function I,e getting some?symbols instead of characters
here are the output screenshots and code screenshots please help me to find a solution
thanks in advance
Use CTRL T to format your code.
Attach your ‘complete’ sketch between code tags, use the </> icon in the posting menu.
[code]Paste your sketch here[/code]
@OP
Try these commands:
char c = (char)sdcard.read();
Serial.print(c);
Please, post your sketch (the program that you have created in the IDE) in this post page. Follow these steps.
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datskunchala:
even after trying the above commands i got same output on
Why are you not posting your code?
Without it we can not try things ourselves, a screen shot does not cut it here.
Nowhere do you define a value for chipselect nor do you set it as an output before you write to it.
#include<SPI.h>
#include<SD.h>
char compare[6] = "start";
int i = 0;
const int chipselect = 10;
File sdcard;
char c;
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
while (!Serial) {
Serial.print("unable to select serial console\n");
;
}
Serial.print("detecting sdcard please wait\n");
if (!SD.begin(chipselect)) {
while (1);
}
Serial.print("sdcard detected \n");
if (SD.exists("text.dat")) {
Serial.print("file already exists\n");
}
File sdcard = SD.open("text.dat", FILE_WRITE);
sdcard.println(compare);
Serial.print("copied text \n");
sdcard.close();
/* OPENING THE SD CARD FILE AGAIN TO READ BACK */
sdcard = SD.open("test.txt");
while(1)
{
Serial.print("-");
char c = (char)sdcard.read();
Serial.print(c);
i++;
if(i> 5) break;
}
sdcard.close();
}
void loop() {
}
I have posted the complete code and I have tried to type cast it to other formats like int char float double and string for INT I am getting value=1 for double=1.00 and for char-? and finally, for string -1(no data found according to Arduino pages ) and sometimes white spaces too with serial.println() command
but I want to read the strings so can you tell me where I am wrong
tried to typecast like this:-
c = (char)sdcard.read();
Serial.print(c);
@OP
Try these:
{
sdcard = SD.open("text.dat", FILE_READ); //you should open that file where you wrote; not 'test.txt"
if (sdcard)
{
while (sdcard.available()) //not while(1)
{
char x = (char)sdcard.read();
Serial.print(x);
}
sdcard.close();
}
else
{
Serial.println("File can't be opened...!");
}
}
thank you very much this solved my problem