Adds Arduino Intro - Whack-a-mole Class

presentations/arduino-intro-2016/talk.md

@@ -7,7 +7,16 @@ lang: en-CA
 colorlinks: true
 ...
 
-# Goals
+## Goals
+
+By the end of this class, you'll:
+
+ - Know how to create programs for Arduino and run them.
+ - Have learned about digital input and output, reading switches and
+   lighting LEDs
+ - Have created a *Whack-a-Mole* type game.
+ - Be prepared to follow Arduino tutorials online and continue
+   exploring.
 
 ## Unlondon
 
@@ -55,17 +64,39 @@ Hacker, Church of the Weird Machine, Odd Duck
 \end{center}
 \end{columns}
 
-## Raphael: The Vital Info
+## Raphael: Day Job
 
-- Manufacturing Engineer
+Mechanical Engineer 
-- Instructor at Fanshawe
+
-- Maker
+ - Working in the medical device industry 
+ - Experience in medical device R&D and Manufacturing 
+ - Teaching SolidWorks CAD at Fanshawe
+
+## Raphael: The Fun Stuff
+
+Thinker, Jack of all Trades - Master of None
+
+\begin{columns}[c]
+\column{0.50\textwidth}
+\begin{itemize}
+ \item Arduino for Fun, and Odd Jobs 
+ \item 3D Printer Hobbyist 
+ \item PC Builder \& Gamer 
+ \item Fish keeper
+\end{itemize}
+\column{0.50\textwidth}
+\begin{center}
+\includegraphics[width=0.80\textwidth]{images/rapha1.png}
+\vspace{5mm}
+\includegraphics[width=0.80\textwidth]{images/rapha2.png}
+\end{center}
+\end{columns}
 
 # What's in your kit?
 
 ## Kit Contents
 
-- Arduino Uno R3 Clone
+- Arduino Uno R3
 - Solderless Breadboard
 - Connecting wires
 - LEDs
@@ -82,14 +113,6 @@ It's a kit (on a board) with the bare minimum components to easily use the $\mu$
 hardware. They do the basic, boring design needed for any board, so users only
 need to add the neat stuff.
 
-<!-- ## Arduino UNO -->
-
-<!-- The Arduino variety that we are using is the Arduino UNO. -->
-
-<!-- - Processor: Atmel Atmega328p -->
-<!-- - Memory: 2K RAM + 32K Flash -->
-<!-- - FT232RL Logic-level Serial$\leftrightarrow$USB Chip -->
-
 ## Arduino Software
 
 The Arduino folks also adapted an *Integrated Development Environment*
@@ -99,27 +122,48 @@ their boards and then write the programs to the $\mu$C.
 \Large Get the Arduino IDE:
 [https://www.arduino.cc/en/Main/Software](https://www.arduino.cc/en/Main/Software)
 
-## Installation 
+<!-- ## Installation  -->
 
-\Large Get installing
+<!-- \Large Get installing -->
 
 # Circuit Basics
 
 ## Current
 
-Current is the flow of charge through a circuit. Conventionally we
+Current is the flow of charge through a circuit. Measured in Amperes
-think of this as happening from HIGH ($+$) to LOW ($-$)
+(\si{\ampere}).
 
-## Voltage / Potential / Resistance
+## Resistance / Impedance
 
-Voltage is how fast the current can move in the circuit. River
+Circuits have a resistance to current flow that depends on the parts
-metaphor: 
+in the circuit. 
 
-  - current = flow rate: ($\si{\liter\per\second}$)
+Measured in Ohms (\si{\ohm})
-  - voltage = change in height: ($\si{\meter}$)
 
-Other devices in a circuit can impede / effect current flow. We'll
+## Voltage
-call them resistance(s).
+
+Voltage is a potential (akin to a pressure) pushing the current
+through a circuit. Current is said to flow from higher (+) voltage
+to lower (-) voltage.
+
+Measured in Volts (\si{\volt})
+ 
+## Ohm's Law; Light
+
+Voltage, Current and Resistance are related to each other.
+
+- As voltage increases, current increases
+- As voltage decreases, current decreases
+- As resistance increases, current decreases
+- As resistance decreases, current increases
+
+## \si{\volt},  \si{\ohm}, \si{\ampere}: The Water Analogy
+
+If charge were water, then:
+
+  - resistance = obstacles blocking flow
+  - current = flow rate
+  - voltage = change in height *or* pressure.
 
 ## Diode
 
@@ -159,8 +203,7 @@ call them resistance(s).
 
 \begin{itemize}
 \item \emph{Resists}/limits the flow of current
-\item Needed for LEDs: $\approx\SI{400}{\ohm}$\\
+\item Needed for LEDs: $\approx\SI{1000}{\ohm}$\\
-(safe for $\le\SI{6}{\volt}$)
 \item Button Pull-up/down: $\ge\SI{10}{\kilo\ohm}$
 \item Color coded, Google it
 \end{itemize}
@@ -170,32 +213,6 @@ call them resistance(s).
 
 \end{columns}
 
-## Ohm's Law
-
-Ohm's Law relates current to potential and resistance.
-
-$$ V = IR $$
-$$ I=\frac{V}{R} $$
-$$ R = \frac{V}{I} $$
-
-* V = Potential in Volts (\si{\volt})
-* I = Current in Amperes (\si{\ampere})
-* R = Resistance in Ohms (\si{\ohm})
-
-## Ohm's Law: Example
-
-The datasheet for an LED says that the maximum continuous current is
-\SI{15}{\milli\ampere}. Your circuit operates at \SI{5}{\volt}\footnotemark[1]. How
-big should your resistor be?
-
-$$ \si{\ohm} = \frac{\SI{5}{\volt}}{\SI{0.015}{\ampere}} = 333.\overline{3}\si{\ohm} $$
-
-How much current for our *cheet sheet* value?
-
-$$ \si{\ampere} = \frac{\SI{5}{\volt}}{\SI{400}{\ohm}} = \SI{12.5}{\milli\ampere} $$
-
-\footnotetext[1]{\tiny Actually, this calculation is inaccurate. LEDs will have a *forward voltage drop* of between \SI{300}{\milli\volt} and \SI{700}{\milli\volt} this should be subtracted from \si{\volt} above... but it's not critical.}
-
 ## Buttons
 
 - Buttons connect _or_ disconnect two wires/parts
@@ -331,19 +348,21 @@ will not flow and the LED is off.
 ## Your first Program
 
 ~~~ C
+#define LED 13
+
 /* the setup function runs once on reset / power */
 void setup() {
-  /* set pin 13 as an output */
+  pinMode(LED, OUTPUT);
-  pinMode(13, OUTPUT);
 }
 
-/* the loop function repeats forever */
+/* loop() repeats until reset or power off */
 void loop() {
-  digitalWrite(13, HIGH);   // turn on LED
+  digitalWrite(LED, HIGH);   // turn on LED
-  delay(1000);              // wait for a second
-  digitalWrite(13, LOW);    // turn the off LED
   delay(1000);              // wait for a second
+  digitalWrite(LED, LOW);    // turn the off LED
+  delay(1000);
 }
+
 ~~~
 
 # Add Some Parts
@@ -363,36 +382,13 @@ $\SI{5}{\volt}$ on the pin marked `5V`, the reference (GND) is marked
 
 ![Arduino + Breadboard](images/bb+uno.png)
 
-<!-- ## Buzzer: Hardware -->
+## Buzzer & Button: Hardware
-
-<!-- \begin{center} -->
-<!-- \includegraphics[width=0.98\textwidth]{images/buzzer-breadboard.png} -->
-<!-- \end{center} -->
-
-<!-- ## Buzzer: Software -->
-
-<!-- ~~~ C -->
-<!-- #define BUZZER 8       /* Make BUZZER same as pin 8 */ -->
-
-<!-- void setup() { -->
-<!--   pinMode(BUZZER, OUTPUT); -->
-<!--   digitalWrite(BUZZER, HIGH);    /* Turn off buzzer */ -->
-<!-- } -->
-<!-- void loop() { -->
-<!--   digitalWrite(BUZZER, LOW);      /* Turn on buzzer */ -->
-<!--   delay(100);                     /* wait for 100ms */ -->
-<!--   digitalWrite(BUZZER, HIGH);    /* Turn off buzzer */ -->
-<!--   delay(900);                         /* wait 900ms */ -->
-<!-- } -->
-<!-- ~~~ -->
-
-## Push Button: Hardware
 
 \begin{center}
-\includegraphics[width=0.98\textwidth]{images/bb+switch.png}
+\includegraphics[width=0.98\textwidth]{images/buzzer-breadboard.png}
 \end{center}
 
-## Push Button: Hardware, Pt. 2
+## Push Button: Zoom
 
 \begin{center}
 \includegraphics[width=0.98\textwidth]{images/bb+switch+zoom.png}
@@ -411,18 +407,24 @@ is floating!
 Connect the pin to Vcc so that it reads High; use a
 resistor to prevent short circuit (limit current).
 
-## Push Button: Software (Part 1)
+## Buzzer: Zoom
+
+\begin{center}
+\includegraphics[width=0.98\textwidth]{images/buzzer-zoom.png}
+\end{center}
+
+## Buzzer / Button: Software (Part 1)
 
 ~~~ C
 #define BUTTON 2
-#define LED 13
+#define BUZZER 8
 
-int button_state = 0;
+int button_state;
 
 void setup() {
   pinMode(BUTTON, INPUT);
-  pinMode(LED, OUTPUT);
+  pinMode(BUZZER, OUTPUT);
-  digitalWrite(LED, LOW); /* Start w/ LED off */
+  digitalWrite(BUZZER, LOW); /* Start w/ LED off */
 }
 ~~~
 ## Programming Note: Variables
@@ -430,7 +432,7 @@ void setup() {
 Declare a variable:
 
 ~~~ C
-int delay_ms = 1000;
+int button_state = HIGH;
 ~~~
 
 `<type> <name> [= <initial value>];` (value optional)
@@ -438,15 +440,6 @@ int delay_ms = 1000;
 It's a name, like a preprocessor `#define`, but the value can change
 at *runtime*
 
-<!-- ## RGB LED -->
-
-<!-- - Three LEDs in the same package. -->
-<!-- - LEDs share the same `GND` ($-$) pin, one ($+$) side of each LED -->
-<!-- - Connect `-` to negative rail, R, G, & B to pins 3,5, & 6 on Arduino -->
-
-<!-- \centering -->
-<!-- \includegraphics[width=0.60\textwidth]{images/bb+uno+led.png} -->
-
 ## Programming Note: *If* Statement
 
 ~~~ C
@@ -470,15 +463,55 @@ In C-like languages, the `==` operator checks if two things
  - It returns `1` if the items are equal, *or*
  - It returns `0` if the items are not equal
 
+## Programming Note: Functions
+
+Functions make it easy to reuse code. You already know / use several
+functions:
+
+ - pinMode
+ - digitalWrite
+ - delay
+ 
+digitalRead(pin number) returns HIGH or LOW depending on current state
+of any **INPUT** pin.
+
+You can write your own functions!
+
+## Programming Note: Writing Functions
+
+~~~ C
+void my_function(int arg1, ...) {
+	// Do fun things
+}
+~~~
+
+void:
+: Return type. Void means nothing returned. Can be any type.
+
+my_function:
+: A name for your function
+
+arguments:
+: A type and name for any parameters you want to use in your function
+from the outside.
+
+Define a function once, you can use it again and again. Better than
+copy/pasting.
+
+
+
 ## Push Button: Software (Part 2)
 
 ~~~ C
+void buzz(int ms) {
+	digitalWrite(BUZZER, HIGH);
+	delay(ms);
+	digitalWrite(BUZZER, LOW);
+}
 void loop() {
   button_state = digitalRead(BUTTON);
-  if (button_state == HIGH) {
+  if (button_state == LOW) {
-    digitalWrite(LED, LOW);
+	buzz(100);
-  } else {
-    digitalWrite(LED, HIGH);
   }
 }
 ~~~
@@ -514,21 +547,24 @@ Connect center pin to `A0`, outer pins to ($+$) and ($-$) rails
 
 ## Pot Code
 
-`analogRead(`*pin*`)` returns the current state of the pin (0--1023),
+`analogRead(`*pin*`)` returns the voltage at the pin (0--1023), it can
-it can be assigned to a variable.
+be used directly or via variable.
 
 ~~~ C
+#define LED 13
+void setup() {
+  pinMode(LED, OUTPUT);
+}
 void loop() {
-  delay_ms = analogRead(A0);
   digitalWrite(LED, HIGH);
-  delay(delay_ms);
+  delay(analogRead(A0));
   digitalWrite(LED, LOW);
+  delay(analogRead(A0));
 }
 ~~~
 
-Each time through the loop, a new `delay_ms` value is read. Since the
+Since the delay() calls use the result of analogRead (0-1023), the
-subsequent delay calls use `delay_ms`, the blink rate changes with
+blink rate changes with knob position.
-knob position.
 
 # Shall we play a game?
 
@@ -538,15 +574,21 @@ knob position.
 \includegraphics[width=0.65\textwidth]{images/bb+switch+pot+leds.png}
 \end{center}
 
+## LEDs, the first one
+
 Looks complicated, but for each LED: The short leg goes to ground, the
 long leg goes to one end of a resistor, and the other end of the
 resistor goes to the arduino pin.
 
+\begin{center}
+\includegraphics[width=0.55\textwidth]{images/one-led.png}
+\end{center}
+
 ## Programming Note: `for` Loop
 
 ~~~ C
 for ( initializer ; condition; increment ) {
-	// This body will repeat until condition != 0
+	// This body will repeat while condition != 0
 }
 ~~~
 
@@ -555,69 +597,106 @@ initializer
 variable.
 
 condition
-: Loop will repeat until condition $\neq0$
+: Loop will repeat while condition is true ($\neq0$)
 
 increment
 : Runs *after* each loop. Often used to increment variables.
 
 \center{*All fields are optional*}
 
-## Game Code: Part. 1; Cylon Attack
+## Cylon Simulator: Part. 1; Pin Setup
+
+~~~ C
+setup() {
+	pinMode(3, OUTPUT);
+	pinMode(4, OUTPUT);
+	pinMode(5, OUTPUT);
+	pinMode(6, OUTPUT);
+	pinMode(7, OUTPUT);
+}
+~~~
+
+## Cylon Simulator: Part. 2
 
 ~~~ C
 loop () {
 	for (int i = 4; i <= 7; i++) {
 		delay_ms = analogRead(A0);
-		analogWrite(i - 1, LOW);
+		digitalWrite(i - 1, LOW);
-		analogWrite(i, HIGH);
+		digitalWrite(i, HIGH);
 		delay(delay_ms);
 	}
 	for (int i = 6; i >= 3; i--) {
 		delay_ms = analogRead(A0);
-		analogWrite(i + 1, LOW);
+		digitalWrite(i + 1, LOW);
-		analogWrite(i, HIGH);
+		digitalWrite(i, HIGH);
 		delay(delay_ms);
 	}
 }
 ~~~
 
-## Programming Note: Functions
+## Programming Note: `while` Loop
 
 ~~~ C
-void my_function(int arg1, ...) {
+while ( statement ) {
-	// Do fun things
+	// This body will repeat while condition is true
+	// True means statement != 0
 }
 ~~~
 
-void:
+initializer
-: Return type. Void means nothing returned. Can be any type.
+: Executed once at beginning of loop. Often used to declare a local
+variable.
 
-my_function:
+condition
-: A name for your function
+: Loop will repeat while condition is true ($\neq0$)
 
-arguments:
+increment
-: A type and name for any parameters you want to use in your function
+: Runs *after* each loop. Often used to increment variables.
-from the outside.
 
-Define a function once, you can use it again and again. Beats
+\center{*All fields are optional*}
-copy/pasting.
 
 ## Winner, Winner, Chicken Dinner
 
 ~~~ C
+#define WINNER 5
 void check_delay(int cur_led, int delay_ms) {
-  if (cur_led != 5) { // No chance of winner
+  unsigned long start = millis();
-    delay(delay_ms);  // Do a normal delay
-    return;
-  }
-  int start = millis();
   while (millis() < start+delay_ms) {
     if (digitalRead(BUTTON) == LOW) {
+      if (cur_led == WINNER) {
+        do_winner();
+      } else {
+        while (digitalRead(BUTTON) == LOW) {
+          do_loser();
+        }
+      }
+    }
+  }
+}
+~~~
+
+## More functions, pt. 1
+~~~ C
+void set_all_leds(int state) {
   for (int i = 3; i <= 7; i++) {
-        digitalWrite(i, HIGH);
+    digitalWrite(i, state);
-	  }; for (;;); // Loop until reset
   }
 }
+
+void do_loser(void) {
+  buzz(500);
+}
+~~~
+
+## More functions, pt. 2
+~~~ C
+void do_winner(void) {
+  set_all_leds(HIGH);
+  buzz(100);
+  delay(100);
+  buzz(100);
+  set_all_leds(LOW);
 }
 ~~~
 
@@ -627,8 +706,8 @@ void check_delay(int cur_led, int delay_ms) {
 loop () {
 	for (int i = 4; i <= 7; i++) {
 		delay_ms = analogRead(A0);
-		analogWrite(i - 1, LOW);
+		digitalWrite(i - 1, LOW);
-		analogWrite(i, HIGH);
+		digitalWrite(i, HIGH);
 		check_delay(i, delay_ms);
 	}
 	for (int i = 6; i >= 3; i--) {
@@ -638,8 +717,89 @@ loop () {
 }
 ~~~
 
-## The End?
+# The End?
 
-\begin{center}
+# Extra Credit
-\LARGE{Let's build some cool stuff!}
+## Ohm's Law
-\end{center}
+
+Ohm's Law relates current to potential and resistance.
+
+$$ V = IR $$
+$$ I=\frac{V}{R} $$
+$$ R = \frac{V}{I} $$
+
+* V = Potential in Volts (\si{\volt})
+* I = Current in Amperes (\si{\ampere})
+* R = Resistance in Ohms (\si{\ohm})
+
+## Ohm's Law: Example
+
+The datasheet for an LED says that the maximum continuous current is
+\SI{15}{\milli\ampere}. Your circuit operates at \SI{5}{\volt}\footnotemark[1]. How
+big should your resistor be?
+
+$$ \si{\ohm} = \frac{\SI{5}{\volt}}{\SI{0.015}{\ampere}} = 333.\overline{3}\si{\ohm} $$
+
+How much current for our *cheet sheet* value?
+
+$$ \si{\ampere} = \frac{\SI{5}{\volt}}{\SI{1}{\kilo\ohm}} = \SI{5}{\milli\ampere} $$
+
+\footnotetext[1]{\tiny Actually, this calculation is inaccurate. LEDs
+will have a *forward voltage drop* of between \SI{1.8}{\volt} and
+\SI{3.3}{\volt} this should be subtracted from \si{\volt} above... but
+it's not critical.}
+
+## Current Limits, Arduino
+
+- No single pin should source more that \SI{20}{\milli\ampere} (\SI{40}{\milli\ampere} is absolute max)
+- Pins are ganged together in groups of 8, no group should source more
+  than \SI{150}{\milli\ampere} total
+- The whole board cannot source more than \SI{200}{\milli\ampere} total
+  
+Practically speaking, this means that the Arduino cannot drive
+speakers, most motors, or anything normally mains powered.
+
+## So\ldots no Arduino smart blender?
+
+You can control almost anything with an arduino, you just can't power
+it with the Arduino. There are various devices that let you switch
+highier powered devices:
+
+ - Transistors
+ - Relays
+ - Solid State Relays
+ - Triac
+ 
+## HIGHs and LOWs
+
+Many different logic levels are in common use: \SI{1.2}{\volt},
+\SI{1.8}{\volt}, \SI{2.5}{\volt}, \SI{3.3}{\volt}, and
+\SI{5}{\volt}. The voltage cited is the *nominal* Vcc of the system.
+
+A HIGH signal is generally any voltage $\geq \frac{2}{3}V_{cc}$.
+
+A LOW signal is generally any voltage $\leq \frac{1}{3}V_{cc}$.
+
+## HIGHs and LOWs, pt. 2
+
+In your travels, you're likely to see both \SI{5}{\volt} and
+\SI{3.3}{\volt} sensors and peripherals.
+
+Since $\SI{3.3}{\volt}\geq\frac{2}{3}V_cc$ your Arduino will accept
+input from a \SI{3.3}{\volt} peripheral without issue.
+
+If you drive an output to \SI{5}{\volt} while it's connected to a
+\SI{3.3}{\volt} peripheral with an Arduino **it will blow up your
+peripheral**.^[In the datasheet for the sensor, it'll have a
+section called *Absolute Maximums*. Generally \SI{3.3}{\volt} parts
+won't accept more that $\approx\SI{3.6}{\volt}$, but some will.]
+
+## HIGHs and LOWs, pt. 3
+
+Solutions:
+
+ - Level Shifter: A dedicated chip that translates between
+   voltages. Available as uni or bidirectional.
+   
+ - Buy a 3.3V Arduino Compatible. Arduinos are available that operate
+   at the lower voltage.

sketchbook/blink/blink.ino

@@ -0,0 +1,12 @@
+#define LED 13
+
+void setup() {
+  pinMode(LED, OUTPUT);
+}
+
+void loop() {
+  digitalWrite(LED, HIGH);   // turn on LED
+  delay(1000);              // wait for a second
+  digitalWrite(LED, LOW);    // turn the off LED
+  delay(1000);
+}

sketchbook/buzz/buzz.ino

@@ -0,0 +1,22 @@
+#define BUZZER 8
+#define BUTTON 2
+
+int button_state;
+
+void setup() {
+  pinMode(BUTTON, INPUT);
+  pinMode(BUZZER, OUTPUT);
+}
+void buzz(int ms) {
+  digitalWrite(BUZZER, HIGH);
+  delay(ms);
+  digitalWrite(BUZZER, LOW);
+}
+
+void loop() {
+  button_state = digitalRead(BUTTON);
+  if (button_state == LOW) {
+    buzz(100);
+  }
+}
+

sketchbook/cylon/cylon.ino

@@ -0,0 +1,24 @@
+int delay_ms;
+
+void setup() {
+  pinMode(3, OUTPUT);
+  pinMode(4, OUTPUT);
+  pinMode(5, OUTPUT);
+  pinMode(6, OUTPUT);
+  pinMode(7, OUTPUT);
+}
+
+void loop() {
+  for (int i = 4; i <= 7; i++) {
+    delay_ms = analogRead(A0);
+    digitalWrite(i - 1, LOW);
+    digitalWrite(i, HIGH);
+    delay(delay_ms);
+  }
+  for (int i = 6; i >= 3; i--) {
+    delay_ms = analogRead(A0);
+    digitalWrite(i + 1, LOW);
+    digitalWrite(i, HIGH);
+    delay(delay_ms);
+  }
+}

sketchbook/variable-blink/variable-blink.ino

@@ -0,0 +1,15 @@
+#define LED 13
+void setup() {
+  pinMode(LED, OUTPUT);
+}
+void loop() {
+  digitalWrite(LED, HIGH);
+  delay(analogRead(A0));
+  digitalWrite(LED, LOW);
+  delay(analogRead(A0));
+}
+
+void buzz(int ms) {
+  return;
+}
+

sketchbook/whack-a-mole/whack-a-mole.ino

@@ -0,0 +1,69 @@
+#define BUTTON 2
+#define BUZZER 8
+#define WINNER 5
+
+int delay_ms;
+
+void setup() {
+  pinMode(BUTTON, INPUT);
+  pinMode(3, OUTPUT);
+  pinMode(4, OUTPUT);
+  pinMode(5, OUTPUT);
+  pinMode(6, OUTPUT);
+  pinMode(7, OUTPUT);
+  pinMode(BUZZER, OUTPUT);
+}
+
+void buzz(int ms) {
+  digitalWrite(BUZZER, HIGH);
+  delay(ms);
+  digitalWrite(BUZZER, LOW);
+}
+
+void set_all_leds(int state) {
+  for (int i = 3; i <= 7; i++) {
+    digitalWrite(i, state);
+  }
+}
+
+void do_winner(void) {
+  set_all_leds(HIGH);
+  buzz(100);
+  delay(100);
+  buzz(100);
+  set_all_leds(LOW);
+}
+
+void do_loser(void) {
+  buzz(500);
+}
+
+void check_delay(int cur_led, int delay_ms) {
+  unsigned long start = millis();
+  while (millis() < start+delay_ms) {
+    if (digitalRead(BUTTON) == LOW) {
+      if (cur_led == WINNER) {
+        do_winner();
+      } else {
+        while (digitalRead(BUTTON) == LOW) {
+          do_loser();
+        }
+      }
+    }
+  }
+}
+
+void loop() {
+  for (int i = 4; i <= 7; i++) {
+    delay_ms = analogRead(A0);
+    digitalWrite(i - 1, LOW);
+    digitalWrite(i, HIGH);
+    check_delay(i, delay_ms);
+  }
+  for (int i = 6; i >= 3; i--) {
+    delay_ms = analogRead(A0);
+    digitalWrite(i + 1, LOW);
+    digitalWrite(i, HIGH);
+    check_delay(i, delay_ms);
+  }
+}