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8 years, 1 month ago.
About read data from SD .txt
Hi, all. Thanks for watching my question. i use LPC4088 board. i have an question about read data from SD .txt Take an example.This is my code.
int main(){
mkdir("/sd/MMA", 0777);
sensorA();
}
void sensorA(){
//Because it's just an example so i don't type my code
//when the sensorA read the data so i printf it to SD .txt
FILE *fp = fopen("/sd/MMA/MMAdata.txt", "a");
fprintf(fp,"%.2f\t",xd*180.0/PI);
fprintf(fp,"%.2f\t",yd*180.0/PI);
fprintf(fp,"%.2f\r\n",zd*180.0/PI);
fclose(fp);
}
And the txt. i insert my SD to computer.It can show like this.
0.91 -0.91 1.29 is the first data.
0.88 -0.88 1.25 is the second data.
and so on.
It is possible to read it like array and save them to buffer ? Thx very much!
1 Answer
8 years, 1 month ago.
Yes, that's fairly easy if the format of the file is always going to be exactly the same.
fscanf is probably the easiest method to do this:
float x[100],y[100],z[100];
int dataPtr = 0;
int readFile() {
FILE *fp = fopen("/sd/MMA/MMAdata.txt", "r");
while (!eof(fp) && (dataPtr<100)) {
fscanf(fp,"%f\t%f\t%f\r\n",x[dataPtr],y[dataPtr],z[dataPtr]);
dataPtr++;
}
fclose(fp);
return dataPtr;
}
If you need to cope with formats that aren't quite so fixed then read the input byte by byte into a char[] until you reach a \n. Replace the \n with 0 (c uses 0 to end strings not a new line) and then use strtok() to split the line into fields based on a separator charactor, tab in this case.