Which LED(s) turn on?

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1 Go to and use the code Which LED(s) turn on? May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 1

2 Lab 3b, 3c The LED Cube ENGR 40M Theo Diamandis Stanford University 04 May 2018

Announcements Prelab 3b is due next week Lab 2b and 3a are due next week Midterm exam has been graded Solutions will be posted after class Homework 4 out tonight Lab 3x: Prelab due for

3 Announcements Prelab 3b is due next week Lab 2b and 3a are due next week Midterm exam has been graded Solutions will be posted after class Homework 4 out tonight Lab 3x: Prelab due for Sunday. If you signed up you will get an from me tonight Your Lab 2b is still due before your section next week May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 3

Midterm Statistics Median: 83.0 Mean: 81.72 Std Dev: 11.

4 Midterm Statistics Median: 83.0 Mean: Std Dev: Midterm Exam Scores frequency scores Solutions & grades will be released after class Regrade requests on Gradescope (1 week) May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 4

Overview Goal: To write display(), which takes a 4 4 4 pattern[][][] array and displays it on the LED cube. Challenges: Electrically, the LED cube actually an 8 8 grid.

5 Overview Goal: To write display(), which takes a pattern[][][] array and displays it on the LED cube. Challenges: Electrically, the LED cube actually an 8 8 grid. We d rather not think about time-division multiplexing. How can we write a function that allows to abstract these hardware details away from our main software? May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 5

6 Decomposition loop() The main Arduino loop calls display() Does one pass through the LEDs (time-division multiplexing) which calls Looks up the LED state getledstate() associated with an anode/cathode pair May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 6

7 loop() delegates to display() void loop() { byte pattern[4][4][4]; // (assemble the LEDs pattern) display(pattern); void display(byte pattern[4][4][4]) { for (byte anum = 0; anum < 8; anum++) { for (byte cnum = 0; cnum < 8; cnum++) { // LED multiplexing code May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 7

8 display() delegates to getledstate() void display(byte pattern[4][4][4]) { for (byte anum = 0; anum < 8; anum++) { for (byte cnum = 0; cnum < 8; cnum++) { byte value = getledstate(pattern, anum, cnum); // LED multiplexing code byte getledstate(byte pattern[4][4][4], byte anum, byte cnum) { // map from (", $) to (&, ', () return pattern[z][y][x]; May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 8

9 Review: Pin multiplexing anode (+) wires cathode ( ) wires May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 9

10 Review: Providing enough current Use a PMOS to provide enough power to the LEDs from Arduino May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 10

(-) wire (column) if value > 0, // deactivate it otherwise // Activate the anode (+) wire (row) // Wait a bit

11 Implementing display() void display(byte pattern[4][4][4]) { for (byte anum = 0; anum < 8; anum++) { for (byte cnum = 0; cnum < 8; cnum++) { byte value = getledstate(pattern, anum, cnum); // Activate the cathode (-) wire (column) if value > 0, // deactivate it otherwise // Activate the anode (+) wire (row) // Wait a bit // Deactivate the anode (+) wire (row) May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 11

multiplexing code byte getledstate(byte pattern[4][4][4], byte anum, byte cnum) { // map from (", $) to

12 display() delegates to getledstate() void display(byte pattern[4][4][4]) { for (byte anum = 0; anum < 8; anum++) { for (byte cnum = 0; cnum < 8; cnum++) { byte value = getledstate(pattern, anum, cnum); // LED multiplexing code byte getledstate(byte pattern[4][4][4], byte anum, byte cnum) { // map from (", $) to (&, ', () return pattern[z][y][x]; May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 12

13 Mapping between 2-D and 3-D May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 13

14 Mapping between 2-D and 3-D We want a function that maps from anode/cathode pairs ", $ (e.g. D6 ) to 3D coordinates &, ', ( May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 14

15 Making the mapping function easier You can reorder the anodes/cathodes however you like. Would a different ordering make the relationship simpler? May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 15

16 Mapping between 2-D and 3-D May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 16

17 Mapping between 2-D and 3-D May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 17

18 Implementing getledstate() void getledstate(byte pattern[4][4][4], byte anum, byte cnum) { x =???; y =???; z =???; return pattern[z][y][x]; (Your function will probably be more than four lines.) May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 18

19 Decomposition loop() The main Arduino loop calls display() Does one pass through the LEDs (time-division multiplexing) which calls Looks up the LED state getledstate() associated with an anode/cathode pair May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 19

$== 0) print("hello!\n"); print("hello!\n"); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z.$

20 A note on coding style Why indentation matters: for(int i = 0; i < 5; i++){ for(int j = 0; j < 2; j++){ if(i == 0 && j == 0) print("hello!\n"); print("hello!\n"); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 20

$TEST_PIN = 3; Watch out for = and == if (x = 3) { // always true print("winning!"); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C.$

21 A few pointers Give variables sensible names byte whichone; byte currentpatternindex; Use constants for things that shouldn t change const byte TEST_PIN = 3; Watch out for = and == if (x = 3) { // always true print("winning!"); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 21

22 A note on coding style I honestly didn't think you could even USE emoji in variable names. Or that there were so many different crying ones. May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 22

23 Planning your breadboard May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 23

24 What makes a good breadboard layout? Easy to follow Wires are relatively direct (and color-coded) No spaghetti-like crossovers Resistors don t touch each other Your cube wiring should also be neat Try to keep fairly compact, to allow for things to add next week! May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 24

Breadboard style Please don t: http://www.

com/forum/phpbb-files/thumbs/t_klee_bb_131.

25 Breadboard style Please don t: May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 25

26 Planning your breadboard May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 26

27 Overview of lab 3c Your task is to get your cube to respond to some sort of input. For most of you, this will involve adding hardware. You choose what you want to do, subject to minimum requirements. May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 27

encouraged) to propose something else, but be sure to tell your TA well in

28 Our suggestions for input Serial data Potentiometer Pushbutton switches (or other switches) Audio Capacitive touch sensing You re free (and encouraged) to propose something else, but be sure to tell your TA well in advance! May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 28

29 Serial data You ve already used the Serial Monitor You can also write computer software to interact with the serial port directly If you only respond to serial data, we ll expect to see some impressive software May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 29

Analog-to-digital converter analogread() reads

println(reading); Serial Monitor: 819 819 May

30 Analog-to-digital converter analogread() reads the voltage on the pin, scaled to be a number between 0 and 1023 void loop() { int reading = analogread(a3); Serial.println(reading); Serial Monitor: May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 30

31 Potentiometer Essentially a variable voltage divider standard symbol internal mechanics photo May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 31

32 Potentiometer Essentially a variable voltage divider R1 and R2 vary with the wiper, but R1 + R2 = constant May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 32

33 Potentiometer Connect the wiper to the analog input Read using analogread() May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 33

34 Audio You can connect an audio output to your Arduino almost. May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 34

35 Audio analogread() the instantaneous value The input will be centered at 2.5 V, so you ll need to process it in software An additional handout guides you through this May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 35

Audio frequency response The ArduinoFFT3 library can process your signal to return a frequency-domain representation Implements the fast Fourier transform, an algorithm which computes a

36 Audio frequency response The ArduinoFFT3 library can process your signal to return a frequency-domain representation Implements the fast Fourier transform, an algorithm which computes a close cousin of the Fourier series An additional handout guides you through this Video: May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 36

37 frequency response E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 37

38 Pushbutton switch SPST, momentary and normally open (sometimes known as push-to-make) May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 38

39 Pushbutton switch: debouncing What we think a switch does: What it actually does: May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 39

called debouncing An additional handout guides you through this

40 Pushbutton switch: debouncing As the switch bounces, the Arduino can register many transitions Dealing with this is called debouncing An additional handout guides you through this May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 40

Programming a pattern Since you ve abstracted away the timemultiplexing part, displaying a pattern consists mainly of filling in the pattern array.

41 Programming a pattern Since you ve abstracted away the timemultiplexing part, displaying a pattern consists mainly of filling in the pattern array. Recall triply-nested loops: for (int z = 0; z < 4; z++) { for (int y = 0; y < 4; y++) { for (int x = 0; x < 4; x++) { pattern[z][y][x] = (some value); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 41

Raindrop pattern The raindrop pattern looks like rain is falling from the top of the cube to the bottom Videos https://youtu.

42 Raindrop pattern The raindrop pattern looks like rain is falling from the top of the cube to the bottom Videos May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 42

43 Raindrop pattern Every time period (say, 150 ms): 1. Move the pattern down by one plane 2. Choose an LED at random in the top plane May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 43

44 Timing and inputs Update the pattern once every (say) second With no inputs, this will work: void loop() { static byte ledon[4][4][4]; updatepattern(ledon); // updates pattern delay(1000); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 44

45 Timing and inputs Stop/start whenever the button is pressed Why won t this work? void loop() { static byte ledon[4][4][4]; static bool running = false; if (running) updatepattern(ledon); // updates pattern if (digitalread(button) == HIGH) running =!running; delay(1000); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 45

Timing and inputs Better: Check button without delay void loop() { static byte ledon[4][4][4]; static bool running = false; static long nextupdatetime = millis(); if (millis() > nextupdatetime) { if

46 Timing and inputs Better: Check button without delay void loop() { static byte ledon[4][4][4]; static bool running = false; static long nextupdatetime = millis(); if (millis() > nextupdatetime) { if (running) updatepattern(ledon); // updates pattern nextupdatetime += 1000; if (digitalread(button) == HIGH) running =!running; May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 46

Complexity requirements Minimum requirement: cubes: 25; 6 6 planes: 35; larger planes: 30 Must do one additional handout, or propose your own Details are in the overview handout Points Hardware

47 Complexity requirements Minimum requirement: cubes: 25; 6 6 planes: 35; larger planes: 30 Must do one additional handout, or propose your own Details are in the overview handout Points Hardware Software 5 No additional hardware (includes serial data) Simple response 10 Minor additional hardware Minor complexity Raindrop pattern 15 Moderate additional hardware Pushbuttons Audio non-frequency Moderate complexity 20 Complex additional hardware Impressive complexity May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 47

48 Programming Review Arrays in C

49 Arrays in C An array is a sequential collection of elements of the same data type e.g. int myarr[7]; declares space for seven ints: myarr[0] myarr[1] myarr[2] myarr[3] myarr[4] myarr[5] myarr[6] These are stored next to each other in memory. May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 49

50 Arrays in C You can access array elements with []: int fourthelement = myarray[3]; myarray[4] = -29; You can iterate over array elements: int sum = 0; for (int i = 0; i < 7; i++) { sum = sum + myarray[i]; Remember, indices start at zero May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 50

Quiz If we have the array declaration unsigned byte x[10]; what are valid ways to iterate over the array? a) for (int i=0; i < 10; i++) Serial.println(x[i]); b) for (int i=0; i <= 10; i++) Serial.

51 Quiz If we have the array declaration unsigned byte x[10]; what are valid ways to iterate over the array? a) for (int i=0; i < 10; i++) Serial.println(x[i]); b) for (int i=0; i <= 10; i++) Serial.println(x[i]); c) for (int i=10; i > 10; i--) Serial.println(x[i]); d) for (int i=9; i >= 0; i--) Serial.println(x[i]); May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 51

52 Warning The compiler will not tell you what went wrong! unsigned byte x[10]; for (int i = 1; i <= 10; i++) Serial.println(x[i]); It will just happily read whatever is in memory after the array, whether it makes sense to or not. If it doesn t make sense, your program may crash without warning or error message. May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 52

myarr[1][0][0] myarr[2][1][0] myarr[3][2][0] myarr[1][0][1] myarr[2][1][1] myarr[3][2][1] myarr[1][0][2] myarr[2][1][2] myarr[3][2][2] myarr[1][0][3] myarr[2][1][3] myarr[3][2][3] myarr[2][2][0]

53 Multidimensional arrays in C Arrays can be multidimensional e.g. int cube[4][4][4]; myarr[3][0][0] myarr[3][0][1] myarr[3][0][2] myarr[3][0][3] myarr[2][0][0] myarr[3][1][0] myarr[2][0][1] myarr[3][1][1] myarr[2][0][2] myarr[3][1][2] myarr[2][0][3] myarr[3][1][3] myarr[1][0][0] myarr[2][1][0] myarr[3][2][0] myarr[1][0][1] myarr[2][1][1] myarr[3][2][1] myarr[1][0][2] myarr[2][1][2] myarr[3][2][2] myarr[1][0][3] myarr[2][1][3] myarr[3][2][3] myarr[2][2][0] myarr[3][3][0] myarr[2][2][1] myarr[3][3][1] myarr[2][2][2] myarr[3][3][2] myarr[2][2][3] myarr[3][3][3] myarr[0][0][0] myarr[1][1][0] myarr[0][0][1] myarr[1][1][1] myarr[0][0][2] myarr[1][1][2] myarr[0][0][3] myarr[1][1][3] myarr[0][1][0] myarr[1][2][0] myarr[2][3][0] myarr[0][1][1] myarr[1][2][1] myarr[2][3][1] myarr[0][1][2] myarr[1][2][2] myarr[2][3][2] myarr[0][1][3] myarr[1][2][3] myarr[2][3][3] myarr[0][2][0] myarr[1][3][0] myarr[0][2][1] myarr[1][3][1] myarr[0][2][2] myarr[1][3][2] myarr[0][2][3] myarr[1][3][3] myarr[0][3][0] myarr[0][3][1] myarr[0][3][2] myarr[0][3][3] May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 53

54 Multidimensional arrays in C You access elements with multiple []: cube[2][0][1] = 1; You iterate using nested loops: int sum = 0; for (int i = 0; i < 4; i++) { for (int j = 0; j < 4; j++) { for (int k = 0; k < 4; k++) { sum = sum + cube[i][j][k]; May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 54

Which LED(s) turn on? May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 1

Which LED(s) turn on? May 4, 2018 E40M Spring 2018 T. Diamandis, J. Plummer, R. Howe, C. Z. Lee 1 Lab 3b, 3c The LED Cube ENGR 40M Theo Diamandis Stanford University 04 May 2018 Overview Goal: To write