F1 in Schools Car - Safety Modulation

Hi, I'm Nicholas, a Year 10 student in Australia.

I'm relatively new to programming and such in general. Our teachers created a STEM class this year for gifted students in the engineering (predominantly) field. We're working on our first project and it is as follows:

1. 3D print a car (suitable for Australian F1 in Schools standards)

2. Create a modification for the car to make the car safer for possible passengers inside, documenting the changes between the cars runs (down the track), proving the change in safety

However, our entire class' (including the teacher) has a lack of experience with the programming side of things for Arduino specifically and could really do with a hand.

The problem lies within the documentation of the change. We are hooking up an Adafruit Feather 32u4 Adalogger to the small cars as we race them down the track to calculate the gyroscope and acceleration of the car and thus, the change when we need our modulation.

We are having troubles logging the data from the code into the SD card properly. The code we have so far is as follows:

// (c) Michael Schoeffler 2017, http://www.mschoeffler.de

#include "Wire.h" // This library allows you to communicate with I2C devices.

#include <SPI.h>

#include <SD.h>

const int MPU_ADDR = 0x68; // I2C address of the MPU-6050. If AD0 pin is set to HIGH, the I2C address will be 0x69.

int16_t accelerometer_x, accelerometer_y, accelerometer_z; // variables for accelerometer raw data

int16_t gyro_x, gyro_y, gyro_z; // variables for gyro raw data

int16_t temperature; // variables for temperature data

char tmp_str[7]; // temporary variable used in convert function

char* convert_int16_to_str(int16_t i) { // converts int16 to string. Moreover, resulting strings will have the same length in the debug monitor.

sprintf(tmp_str, "%6d", i);

return tmp_str;

const int chipSelect = 4;

}

void setup() {

Serial.begin(9600);

while (!Serial) {

; // wait for serial port to connect. Needed for native USB port only

}

Serial.print("Initializing SD card...");

// see if the card is present and can be initialized:

if (!SD.begin(4)) {

Serial.println("Card failed, or not present");

// don't do anything more:

while (1);

}

Serial.println("card initialized.");

Wire.begin();

Wire.beginTransmission(MPU_ADDR); // Begins a transmission to the I2C slave (GY-521 board)

Wire.write(0x6B); // PWR_MGMT_1 register

Wire.write(0); // set to zero (wakes up the MPU-6050)

Wire.endTransmission(true);

}

void loop() {

// make a string for assembling the data to log:

String dataString = "";

// read three sensors and append to the string:

for (int analogPin = 0; analogPin < 3; analogPin++) {

int sensor = analogRead(analogPin);

dataString += String(sensor);

if (analogPin < 2) {

dataString += ", ";

}

}

// 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(dataString);

dataFile.close();

// print to the serial port too:

Serial.println(dataString);

}

// if the file isn't open, pop up an error:

else {

Serial.println("error opening datalog.txt");

}

Wire.beginTransmission(MPU_ADDR);

Wire.write(0x3B); // starting with register 0x3B (ACCEL_XOUT_H) [MPU-6000 and MPU-6050 Register Map and Descriptions Revision 4.2, p.40]

Wire.endTransmission(false); // the parameter indicates that the Arduino will send a restart. As a result, the connection is kept active.

Wire.requestFrom(MPU_ADDR, 7*2, true); // request a total of 7*2=14 registers

// "Wire.read()<<8 | Wire.read();" means two registers are read and stored in the same variable

accelerometer_x = Wire.read()<<8 | Wire.read(); // reading registers: 0x3B (ACCEL_XOUT_H) and 0x3C (ACCEL_XOUT_L)

accelerometer_y = Wire.read()<<8 | Wire.read(); // reading registers: 0x3D (ACCEL_YOUT_H) and 0x3E (ACCEL_YOUT_L)

accelerometer_z = Wire.read()<<8 | Wire.read(); // reading registers: 0x3F (ACCEL_ZOUT_H) and 0x40 (ACCEL_ZOUT_L)

temperature = Wire.read()<<8 | Wire.read(); // reading registers: 0x41 (TEMP_OUT_H) and 0x42 (TEMP_OUT_L)

gyro_x = Wire.read()<<8 | Wire.read(); // reading registers: 0x43 (GYRO_XOUT_H) and 0x44 (GYRO_XOUT_L)

gyro_y = Wire.read()<<8 | Wire.read(); // reading registers: 0x45 (GYRO_YOUT_H) and 0x46 (GYRO_YOUT_L)

gyro_z = Wire.read()<<8 | Wire.read(); // reading registers: 0x47 (GYRO_ZOUT_H) and 0x48 (GYRO_ZOUT_L)

// print out data

Serial.print("aX = "); Serial.print(convert_int16_to_str(accelerometer_x));

Serial.print(" | aY = "); Serial.print(convert_int16_to_str(accelerometer_y));

Serial.print(" | aZ = "); Serial.print(convert_int16_to_str(accelerometer_z));

// the following equation was taken from the documentation [MPU-6000/MPU-6050 Register Map and Description, p.30]

Serial.print(" | tmp = "); Serial.print(temperature/340.00+36.53);

Serial.print(" | gX = "); Serial.print(convert_int16_to_str(gyro_x));

Serial.print(" | gY = "); Serial.print(convert_int16_to_str(gyro_y));

Serial.print(" | gZ = "); Serial.print(convert_int16_to_str(gyro_z));

Serial.println();

// delay

delay(50);

}

If anyone could tell me where we are going wrong, it would be greatly appreciated. Thanks in advance!