Arduino is incorrectly reading bytes from a file on SD card.
I have a file containing bytes where each set of 2 bytes represents an integer, which I copy over to the arduino sd card. I generated a sample file with c++ on computer, simply counting up:
#include <iostream>
#include <fstream>
using namespace std;
int main() {
ofstream file;
file.open("record.txt");
const int n = 128;
char buffer[n];
for (int i=0; i<n; i+=2) {
buffer[i] = i/2 & 0xFF;
buffer[i+1] = i/2 >> 8;
}
file.write(buffer,n);
file.close();
}
On my computer I can read back the values with:
file.read(buffer,n);
for (int i=0; i<128; i+=2) {
unsigned char lower = buffer[i];
unsigned char upper = buffer[i+1];
unsigned short value = (upper << 8) | lower;
cout << value << endl;
}
I am trying to get the arduino to read this file from the sd card, and simply print it through serial.
However, the output is just random values. Am I doing something wrong in the file reading or byte array?
What's going wrong?
Arduino code:
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
void setup() {
Serial.begin(9600);
// Initialize the SD card
if (!(SD.begin(4))) {
// stop here if no SD card
while (1) {
Serial.println("Unable to access the SD card");
delay(500);
}
}
}
void loop() {
if (SD.exists("record.txt")) {
// open file
File audiofile = SD.open("record.txt", FILE_READ);
// read one chunk of data
byte buffer1[128];
audioFile.read(buffer1, 128);
// print over serial
for (int i = 0; i < 128; i += 2) {
unsigned char lower = buffer1[i];
unsigned char upper = buffer1[i + 1];
unsigned short value = (upper << 8) | lower;
Serial.println(value);
}
} else {
Serial.println("No aud on teensyio data saved");
}
}
I am getting serial output like this:
15962
0
4887
0
37900
8191
8224
0
0
0
32668
8192
65528
4095
7423
0
8192
0
37804
8191
2
0
7571
0
37804