Data Logger (and using cool sensors!)

A lab report by Ryan Curtis.

In The Report

Include your responses to the bold questions on your own fork of this lab report template. Include snippets of code that explain what you did. Deliverables are due next Tuesday. Post your lab reports as README.md pages on your GitHub, and post a link to that on your main class hub page.

For this lab, we will be experimenting with a variety of sensors, sending the data to the Arduino serial monitor, writing data to the EEPROM of the Arduino, and then playing the data back.

Part A. Writing to the Serial Monitor

a. Based on the readings from the serial monitor, what is the range of the analog values being read? The values range between 0-1023.

b. How many bits of resolution does the analog to digital converter (ADC) on the Arduino have? There are 10 bits of resolution.

Part B. RGB LED

How might you use this with only the parts in your kit? Show us your solution. I created a button to toggle the color of the RGB LED: video

Part C. Voltage Varying Sensors

1. FSR, Flex Sensor, Photo cell, Softpot

a. What voltage values do you see from your force sensor? It outputs values 0-255 and reads values 0 to ~990.

b. What kind of relationship does the voltage have as a function of the force applied? (e.g., linear?) It would spike when force was applied sinusoidally and then drop back down when the force is removed.

c. Can you change the LED fading code values so that you get the full range of output voltages from the LED when using your FSR? Divide the value being read by the fsr by 4 to scale the value into the range of 0-255 so the LED will output its full range.

d. What resistance do you need to have in series to get a reasonable range of voltages from each sensor? A resistance of about 30k provides a range of resistances between 100-1000.

e. What kind of relationship does the resistance have as a function of stimulus? (e.g., linear?) Like voltages, resistances are almost a sinusoidal relationship to the stimulus. When stimulus is applied, it increases dramatically and then when its removed it drops dramatically. It is like a sigmoidal activation function.

2. Accelerometer

a. Include your accelerometer read-out code in your write-up.

int greenPin = 10;
int bluePin = 9;
 
// software SPI
//Adafruit_LIS3DH lis = Adafruit_LIS3DH(LIS3DH_CS, LIS3DH_MOSI, LIS3DH_MISO, LIS3DH_CLK);
// hardware SPI
//Adafruit_LIS3DH lis = Adafruit_LIS3DH(LIS3DH_CS);
// I2C
Adafruit_LIS3DH lis = Adafruit_LIS3DH(A4,A5);

void setup() {
  lis.setRange(LIS3DH_RANGE_4_G);   // 2, 4, 8 or 16 G!
  Serial.print("Range = "); Serial.print(2 << lis.getRange());  

}

void loop() {
  // put your main code here, to run repeatedly:
  lis.read();
  red = (lis.x)(lis.x)*255/4;
  green = (lis.y)(lis.y)*255/4;
  blue = (lis.z)(lis.z)*255/4;
  
  setColor(red, green, blue);  // green
  delay(500);
  
}

void setColor(int red, int green, int blue)
{
  #ifdef COMMON_ANODE
    red = 255 - red;
    green = 255 - green;
    blue = 255 - blue;
  #endif
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);  
}

Part D. Logging values to the EEPROM and reading them back

1. Reading and writing values to the Arduino EEPROM

a. Does it matter what actions are assigned to which state? Why? No. The states are arbirtarily assigned between the different sensor values and can be in any order.

b. Why is the code here all in the setup() functions and not in the loop() functions? Because upon entering the states it runs the code to execute on eeprom once and then it is done and is in the state.

c. How many byte-sized data samples can you store on the Atmega328? 1024 bytes can be stored

d. How would you get analog data from the Arduino analog pins to be byte-sized? How about analog data from the I2C devices? Read the analog data from the pins and encode it as 8 bits representing values 0-255 using binary.

e. Alternately, how would we store the data if it were bigger than a byte? (hint: take a look at the EEPROMPut example) use multiple bytes that are adjacent to each other and increment your location in EEPROM by the size of what you store to avoid interfering with the data.

Upload your modified code that takes in analog values from your sensors and prints them back out to the Arduino Serial Monitor.

void setup() {

  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

}

void loop() {   
  // read the input on analog pin 0:
  int sensorValue = analogRead(A0);
  
  int eeAddress = 0;   //Location we want the data to be put.

  //One simple call, with the address first and the object second.
  EEPROM.put(eeAddress, sensorValue);

  Serial.println("Written int data type!");

  eeAddress += sizeof(int); //Move address to the next byte after float 'f'.

  EEPROM.get(eeAddress, f);
  Serial.print(f);
 }

2. Design your logger

a. Insert here a copy of your final state diagram. image;

3. Create your data logger!

a. Record and upload a short demo video of your logger in action. The speaker acts like a microphone and when the button is not pressed and then when the button is pressed it plays back the audio through the speaker. code1 code2 code3 video