Why Arduino int can't count over 14464? - arduino

Question

I got some problem about reading from MPU6050 and then write to SD card.
Actually I could successfully do the read-and-write, but I found Arduino UNO can't count over 14464!?
I set every line of my data that is:
count, time(millis()), ax, ay, az, gx, gy, gz
It could record the data right till count to 14464 (I) and it will end the loop automated.
It really bothers me... and it seems no one face this problem before.
Here is my code:
#include "I2Cdev.h"
#include "MPU6050.h"
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif
MPU6050 accelgyro;
//SD card here
#include <SPI.h>
#include <SD.h>
File myFile;
//////////Global Variable Here//////////
int16_t ax, ay, az;
int16_t gx, gy, gz;
int count = 1;
//set sec & count_limit
int set_time = 1000 * 60;
int count_limit = 80000;
int BTN = 7;
// uncomment "OUTPUT_READABLE_ACCELGYRO" if you want to see a tab-separated
// list of the accel X/Y/Z and then gyro X/Y/Z values in decimal. Easy to read,
// not so easy to parse, and slow(er) over UART.
#define OUTPUT_READABLE_ACCELGYRO
//Set LED
#define R_PIN 8
#define G_PIN 9
bool blinkState_R = false;
bool blinkState_G = false;
void setup() {
// configure Arduino LED for
pinMode(R_PIN, OUTPUT);
pinMode(G_PIN, OUTPUT);
pinMode(BTN, INPUT);
digitalWrite(G_PIN, HIGH);
// join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
Wire.begin();
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
Fastwire::setup(400, true);
#endif
// initialize serial communication
// (38400 chosen because it works as well at 8MHz as it does at 16MHz, but
// it's really up to you depending on your project)
Serial.begin(38400);
// initialize device
Serial.println("Initializing I2C devices...");
accelgyro.initialize();
accelgyro.setFullScaleAccelRange(MPU6050_ACCEL_FS_2);
// verify connection
Serial.println("Testing device connections...");
Serial.println(accelgyro.testConnection() ? "MPU6050 connection successful" : "MPU6050 connection failed");
// use the code below to change accel/gyro offset values
accelgyro.setXGyroOffset(59);
accelgyro.setYGyroOffset(42);
accelgyro.setZGyroOffset(-8);
accelgyro.setXAccelOffset(1359);
accelgyro.setYAccelOffset(-1620);
accelgyro.setZAccelOffset(1917);
/////////////////////////////////////////////////////////////////////
//SD card Initailize
/////////////////////////////////////////////////////////////////////
Serial.print("Initializing SD card...");
if (!SD.begin(4)) {
Serial.println("initialization failed!");
digitalWrite(R_PIN, HIGH);
return;
}
Serial.println("initialization done.");
digitalWrite(R_PIN, LOW);
if (SD.exists("example.txt")) {
Serial.println("example.txt exists.");
}
else {
Serial.println("example.txt doesn't exist.");
}
// open a new file and immediately close it:
Serial.println("Creating example.txt...");
myFile = SD.open("example.txt", FILE_WRITE);
myFile.close();
// Check to see if the file exists:
if (SD.exists("example.txt")) {
Serial.println("example.txt exists.");
}
else {
Serial.println("example.txt doesn't exist.");
}
// delete the file:
Serial.println("Removing example.txt...");
SD.remove("example.txt");
if (SD.exists("example.txt")) {
Serial.println("example.txt exists.");
}
else {
Serial.println("example.txt doesn't exist.");
}
delay(3000);
////////////////////////////////////////////////////////////////////////////////
//SD END
////////////////////////////////////////////////////////////////////////////////
digitalWrite(G_PIN, LOW);
}
void loop() {
// read raw accel/gyro measurements from device
accelgyro.getMotion6(&ax, &ay, &az, &gx, &gy, &gz);
blinkState_R = !blinkState_R;
digitalWrite(R_PIN, blinkState_R);
// these methods (and a few others) are also available
//accelgyro.getAcceleration(&ax, &ay, &az);
//accelgyro.getRotation(&gx, &gy, &gz);
////////////////////////////////////////////
// Write to SD Card
///////////////////////////////////////////
// write data to file
if(count <= count_limit ){
myFile = SD.open("IMU_LOG.txt", FILE_WRITE);
Serial.print(count);Serial.print("\t"); myFile.print(count); myFile.print("\t");
Serial.print(millis()); Serial.print("\t"); myFile.print(millis()); myFile.print("\t");
Serial.print(ax); Serial.print("\t"); myFile.print(ax); myFile.print("\t");
Serial.print(ay); Serial.print("\t"); myFile.print(ay); myFile.print("\t");
Serial.print(az); Serial.print("\t"); myFile.print(az); myFile.print("\t");
Serial.print(gx); Serial.print("\t"); myFile.print(gx); myFile.print("\t");
Serial.print(gy); Serial.print("\t"); myFile.print(gy); myFile.print("\t");
Serial.print(gz); Serial.print("\n"); myFile.print(gz); myFile.print("\n");
myFile.close();
delay(5);
blinkState_G = !blinkState_G;
digitalWrite(G_PIN, blinkState_G);
}else{
while(1){
Serial.print("Process done.\n");
digitalWrite(G_PIN, OUTPUT);
delay(2000);
}
count= count + 1 ;
}

Answer 1

You should be getting a compiler warning here.
int count_limit = 80000;
The maximum value of int on your platform is 32,767. When you set an int to something larger, the behavior is undefined, which is bad news because it means that your program is incorrect.
In this particular case, you might notice that 80000 = 14464 + 216, which explains why it stopped at 14464, if int is 16 bits long.
You will need to use long if you want to count higher than 65,535.
long count_limit = 80000L;
long count = 1;