A better mapping with map()

1/*
2  MapDemo -- A simple program to demonstrate converting the 0..1023  values from the analog to digital converter (ADC) inputs to a more useful range  for human consuption of 0..10.
3  The reason for this demo is not to read any  actual values, but to show a technique for getting the most even distribution of  values from the map function. The technique used is
4  not entirely intuitive  after reading the Arduino reference page at: https://www.arduino.cc/reference/en/language/functions/math/map/
5
6  This program is public domain and comes with no warranty of any kind. 
7*/
8
9void  setup() {
10  
11  // Turn the built-in LED on to indicate program is starting.
12  pinMode(LED_BUILTIN, OUTPUT);
13  digitalWrite(LED_BUILTIN, HIGH);
14
15  //  Initialize serial communication and delay to give time to start the serial console.
16  Serial.begin(9600);
17  delay(10000);
18
19  // Turn off the built-in LED to  indicate startup is done.
20  digitalWrite(LED_BUILTIN, LOW);
21}
22
23void  loop() {
24
25  // All these loop map 0 through 1023 onto 0 through 10, but in  different ways.
26
27  // This seems logigal. The ADC from value ranges 0..1023  and the to value ranges 0..10, with 0 meaning no LEDs lit. But, there's a problem.  The distribution is not even. Only one analog value maps to 10. 
28  for (int x=0;  x<1024; x++) {
29    int y = map(x, 0, 1023, 0, 10);
30    Serial.print("y =  map(x, 0, 1023, 0, 10): x = ");
31    Serial.print(x);
32    Serial.print(",  y = ");
33    Serial.println(y);
34  }
35
36  // This way is not as intuitive,  as it seems to be mapping the impossible to obtain ADC value 1024 to the impossible  to display value of 11. But, it works and it gives a more even distribution of values.
37  for (int x=0; x<1024; x++) {
38    int y = map(x, 0, 1024, 0, 11);
39    Serial.print("y  = map(x, 0, 1024, 0, 11): x = ");
40    Serial.print(x);
41    Serial.print(",  y = ");
42    Serial.println(y);
43  }
44
45  // There's also the mathematical  way of doing it using slope-intercept form: y = mx + b where the slope (m) is found  by the ratio of the two ranges and the y intersection is 0.
46  // See: https://en.wikipedia.org/wiki/Linear_equation#Slope-intercept_form
47  // Since the intersection with the y-axis is at 0, we can ignore it and the equation  simplifies to y = mx.
48  // The value of m (slope) can be found using the concept  of rise over run. The rise is the change in y value, so 0..11 in our case. The run  is the change in x, or 0..1024. So m = 11 /1024.
49  for (int x=0; x<1024; x++)  {
50    int y = (int) 11 * x / 1024;
51    Serial.print("y = (int) 11 * x / 1024:  x = ");
52    Serial.print(x);
53    Serial.print(", y = ");
54    Serial.println(y);
55  }
56
57  // Pause and wait for any kind of input before running again.
58  Serial.println("Send  any serial input to run again.");
59  while (!Serial.available());
60  Serial.read();
61}

1/* 
2  Bargraph Meter -- Light a single LED in a 10-segment bargraph   to indicate input voltage at analog pin.
3  No LEDs are lit below the lowest threshold.
4
5   Code by Alex Horton
6  Public domain with no warranty or guaranty as to fitness   of purpose.
7*/
8
9int analogValue = 0;
10int level = 0;
11
12void setup()   {
13  Serial.begin(9600);
14  pinMode(13,OUTPUT);
15  pinMode(12,OUTPUT);
16   pinMode(11,OUTPUT);
17  pinMode(10,OUTPUT);
18  pinMode(9,OUTPUT);
19  pinMode(8,OUTPUT);
20   pinMode(7,OUTPUT);
21  pinMode(6,OUTPUT);
22  pinMode(5,OUTPUT);
23  pinMode(4,OUTPUT);
24   pinMode(A5,INPUT);
25}
26
27void loop() {
28  analogValue = analogRead(A5);
29   level = map(analogValue, 0, 1024, 0, 11);
30  Serial.println(level);
31  Serial.println(analogValue);
32
33   switch (level) {
34    case 0:
35      digitalWrite(13,LOW);
36      digitalWrite(12,LOW);
37       digitalWrite(11,LOW);
38      digitalWrite(10,LOW);
39      digitalWrite(9,LOW);
40       digitalWrite(8,LOW);
41      digitalWrite(7,LOW);
42      digitalWrite(6,LOW);
43       digitalWrite(5,LOW);
44      digitalWrite(4,LOW);
45    break;
46    case   1:
47      digitalWrite(13,LOW);
48      digitalWrite(12,LOW);
49      digitalWrite(11,LOW);
50       digitalWrite(10,LOW);
51      digitalWrite(9,LOW);
52      digitalWrite(8,LOW);
53       digitalWrite(7,LOW);
54      digitalWrite(6,LOW);
55      digitalWrite(5,LOW);
56       digitalWrite(4,HIGH);
57    break;
58    case 2:
59      digitalWrite(13,LOW);
60       digitalWrite(12,LOW);
61      digitalWrite(11,LOW);
62      digitalWrite(10,LOW);
63       digitalWrite(9,LOW);
64      digitalWrite(8,LOW);
65      digitalWrite(7,LOW);
66       digitalWrite(6,LOW);
67      digitalWrite(5,HIGH);
68      digitalWrite(4,LOW);
69     break;
70    case 3:
71      digitalWrite(13,LOW);
72      digitalWrite(12,LOW);
73       digitalWrite(11,LOW);
74      digitalWrite(10,LOW);
75      digitalWrite(9,LOW);
76       digitalWrite(8,LOW);
77      digitalWrite(7,LOW);
78      digitalWrite(6,HIGH);
79       digitalWrite(5,LOW);
80      digitalWrite(4,LOW);
81    break;
82    case   4:
83      digitalWrite(13,LOW);
84      digitalWrite(12,LOW);
85      digitalWrite(11,LOW);
86       digitalWrite(10,LOW);
87      digitalWrite(9,LOW);
88      digitalWrite(8,LOW);
89       digitalWrite(7,HIGH);
90      digitalWrite(6,LOW);
91      digitalWrite(5,LOW);
92       digitalWrite(4,LOW);
93    break;
94    case 5:
95      digitalWrite(13,LOW);
96       digitalWrite(12,LOW);
97      digitalWrite(11,LOW);
98      digitalWrite(10,LOW);
99       digitalWrite(9,LOW);
100      digitalWrite(8,HIGH);
101      digitalWrite(7,LOW);
102       digitalWrite(6,LOW);
103      digitalWrite(5,LOW);
104      digitalWrite(4,LOW);
105     break;
106    case 6:
107      digitalWrite(13,LOW);
108      digitalWrite(12,LOW);
109       digitalWrite(11,LOW);
110      digitalWrite(10,LOW);
111      digitalWrite(9,HIGH);
112       digitalWrite(8,LOW);
113      digitalWrite(7,LOW);
114      digitalWrite(6,LOW);
115       digitalWrite(5,LOW);
116      digitalWrite(4,LOW);
117    break;
118    case   7:
119      digitalWrite(13,LOW);
120      digitalWrite(12,LOW);
121      digitalWrite(11,LOW);
122       digitalWrite(10,HIGH);
123      digitalWrite(9,LOW);
124      digitalWrite(8,LOW);
125       digitalWrite(7,LOW);
126      digitalWrite(6,LOW);
127      digitalWrite(5,LOW);
128       digitalWrite(4,LOW);
129    break;
130    case 8:
131      digitalWrite(13,LOW);
132       digitalWrite(12,LOW);
133      digitalWrite(11,HIGH);
134      digitalWrite(10,LOW);
135       digitalWrite(9,LOW);
136      digitalWrite(8,LOW);
137      digitalWrite(7,LOW);
138       digitalWrite(6,LOW);
139      digitalWrite(5,LOW);
140      digitalWrite(4,LOW);
141     break;
142    case 9:
143      digitalWrite(13,LOW);
144      digitalWrite(12,HIGH);
145       digitalWrite(11,LOW);
146      digitalWrite(10,LOW);
147      digitalWrite(9,LOW);
148       digitalWrite(8,LOW);
149      digitalWrite(7,LOW);
150      digitalWrite(6,LOW);
151       digitalWrite(5,LOW);
152      digitalWrite(4,LOW);
153    break;
154    case   10:
155      digitalWrite(13,HIGH);
156      digitalWrite(12,LOW);
157      digitalWrite(11,LOW);
158       digitalWrite(10,LOW);
159      digitalWrite(9,LOW);
160      digitalWrite(8,LOW);
161       digitalWrite(7,LOW);
162      digitalWrite(6,LOW);
163      digitalWrite(5,LOW);
164       digitalWrite(4,LOW);
165    break;
166  }
167}

1/* 
2  Bargraph Meter -- Light a single LED in a 10-segment bargraph  to indicate input voltage at analog pin.
3  No LEDs are lit below the lowest threshold.
4
5  Code by Alex Horton
6  Public domain with no warranty or guaranty as to fitness  of purpose.
7*/
8
9int analogValue = 0;
10int level = 0;
11
12void setup()  {
13  Serial.begin(9600);
14  pinMode(13,OUTPUT);
15  pinMode(12,OUTPUT);
16  pinMode(11,OUTPUT);
17  pinMode(10,OUTPUT);
18  pinMode(9,OUTPUT);
19  pinMode(8,OUTPUT);
20  pinMode(7,OUTPUT);
21  pinMode(6,OUTPUT);
22  pinMode(5,OUTPUT);
23  pinMode(4,OUTPUT);
24  pinMode(A5,INPUT);
25}
26
27void loop() {
28  analogValue = analogRead(A5);
29  level = map(analogValue, 0, 1024, 0, 11);
30  Serial.println(level);
31  Serial.println(analogValue);
32
33  switch (level) {
34    case 0:
35      digitalWrite(13,LOW);
36      digitalWrite(12,LOW);
37      digitalWrite(11,LOW);
38      digitalWrite(10,LOW);
39      digitalWrite(9,LOW);
40      digitalWrite(8,LOW);
41      digitalWrite(7,LOW);
42      digitalWrite(6,LOW);
43      digitalWrite(5,LOW);
44      digitalWrite(4,LOW);
45    break;
46    case  1:
47      digitalWrite(13,LOW);
48      digitalWrite(12,LOW);
49      digitalWrite(11,LOW);
50      digitalWrite(10,LOW);
51      digitalWrite(9,LOW);
52      digitalWrite(8,LOW);
53      digitalWrite(7,LOW);
54      digitalWrite(6,LOW);
55      digitalWrite(5,LOW);
56      digitalWrite(4,HIGH);
57    break;
58    case 2:
59      digitalWrite(13,LOW);
60      digitalWrite(12,LOW);
61      digitalWrite(11,LOW);
62      digitalWrite(10,LOW);
63      digitalWrite(9,LOW);
64      digitalWrite(8,LOW);
65      digitalWrite(7,LOW);
66      digitalWrite(6,LOW);
67      digitalWrite(5,HIGH);
68      digitalWrite(4,LOW);
69    break;
70    case 3:
71      digitalWrite(13,LOW);
72      digitalWrite(12,LOW);
73      digitalWrite(11,LOW);
74      digitalWrite(10,LOW);
75      digitalWrite(9,LOW);
76      digitalWrite(8,LOW);
77      digitalWrite(7,LOW);
78      digitalWrite(6,HIGH);
79      digitalWrite(5,LOW);
80      digitalWrite(4,LOW);
81    break;
82    case  4:
83      digitalWrite(13,LOW);
84      digitalWrite(12,LOW);
85      digitalWrite(11,LOW);
86      digitalWrite(10,LOW);
87      digitalWrite(9,LOW);
88      digitalWrite(8,LOW);
89      digitalWrite(7,HIGH);
90      digitalWrite(6,LOW);
91      digitalWrite(5,LOW);
92      digitalWrite(4,LOW);
93    break;
94    case 5:
95      digitalWrite(13,LOW);
96      digitalWrite(12,LOW);
97      digitalWrite(11,LOW);
98      digitalWrite(10,LOW);
99      digitalWrite(9,LOW);
100      digitalWrite(8,HIGH);
101      digitalWrite(7,LOW);
102      digitalWrite(6,LOW);
103      digitalWrite(5,LOW);
104      digitalWrite(4,LOW);
105    break;
106    case 6:
107      digitalWrite(13,LOW);
108      digitalWrite(12,LOW);
109      digitalWrite(11,LOW);
110      digitalWrite(10,LOW);
111      digitalWrite(9,HIGH);
112      digitalWrite(8,LOW);
113      digitalWrite(7,LOW);
114      digitalWrite(6,LOW);
115      digitalWrite(5,LOW);
116      digitalWrite(4,LOW);
117    break;
118    case  7:
119      digitalWrite(13,LOW);
120      digitalWrite(12,LOW);
121      digitalWrite(11,LOW);
122      digitalWrite(10,HIGH);
123      digitalWrite(9,LOW);
124      digitalWrite(8,LOW);
125      digitalWrite(7,LOW);
126      digitalWrite(6,LOW);
127      digitalWrite(5,LOW);
128      digitalWrite(4,LOW);
129    break;
130    case 8:
131      digitalWrite(13,LOW);
132      digitalWrite(12,LOW);
133      digitalWrite(11,HIGH);
134      digitalWrite(10,LOW);
135      digitalWrite(9,LOW);
136      digitalWrite(8,LOW);
137      digitalWrite(7,LOW);
138      digitalWrite(6,LOW);
139      digitalWrite(5,LOW);
140      digitalWrite(4,LOW);
141    break;
142    case 9:
143      digitalWrite(13,LOW);
144      digitalWrite(12,HIGH);
145      digitalWrite(11,LOW);
146      digitalWrite(10,LOW);
147      digitalWrite(9,LOW);
148      digitalWrite(8,LOW);
149      digitalWrite(7,LOW);
150      digitalWrite(6,LOW);
151      digitalWrite(5,LOW);
152      digitalWrite(4,LOW);
153    break;
154    case  10:
155      digitalWrite(13,HIGH);
156      digitalWrite(12,LOW);
157      digitalWrite(11,LOW);
158      digitalWrite(10,LOW);
159      digitalWrite(9,LOW);
160      digitalWrite(8,LOW);
161      digitalWrite(7,LOW);
162      digitalWrite(6,LOW);
163      digitalWrite(5,LOW);
164      digitalWrite(4,LOW);
165    break;
166  }
167}

1/*
2  MapDemo -- A simple program to demonstrate converting the 0..1023
3  values from the analog to digital converter (ADC) inputs to a more useful range
4  for human consuption of 0..10.
5  The reason for this demo is not to read any
6  actual values, but to show a technique for getting the most even distribution of
7  values from the map function. The technique used is
8  not entirely intuitive
9  after reading the Arduino reference page at: https://www.arduino.cc/reference/en/language/functions/math/map/
10
11
12  This program is public domain and comes with no warranty of any kind. 
13*/
14
15void
16  setup() {
17  
18  // Turn the built-in LED on to indicate program is starting.
19
20  pinMode(LED_BUILTIN, OUTPUT);
21  digitalWrite(LED_BUILTIN, HIGH);
22
23  //
24  Initialize serial communication and delay to give time to start the serial console.
25
26  Serial.begin(9600);
27  delay(10000);
28
29  // Turn off the built-in LED to
30  indicate startup is done.
31  digitalWrite(LED_BUILTIN, LOW);
32}
33
34void
35  loop() {
36
37  // All these loop map 0 through 1023 onto 0 through 10, but in
38  different ways.
39
40  // This seems logigal. The ADC from value ranges 0..1023
41  and the to value ranges 0..10, with 0 meaning no LEDs lit. But, there's a problem.
42  The distribution is not even. Only one analog value maps to 10. 
43  for (int x=0;
44  x<1024; x++) {
45    int y = map(x, 0, 1023, 0, 10);
46    Serial.print("y =
47  map(x, 0, 1023, 0, 10): x = ");
48    Serial.print(x);
49    Serial.print(",
50  y = ");
51    Serial.println(y);
52  }
53
54  // This way is not as intuitive,
55  as it seems to be mapping the impossible to obtain ADC value 1024 to the impossible
56  to display value of 11. But, it works and it gives a more even distribution of values.
57
58  for (int x=0; x<1024; x++) {
59    int y = map(x, 0, 1024, 0, 11);
60    Serial.print("y
61  = map(x, 0, 1024, 0, 11): x = ");
62    Serial.print(x);
63    Serial.print(",
64  y = ");
65    Serial.println(y);
66  }
67
68  // There's also the mathematical
69  way of doing it using slope-intercept form: y = mx + b where the slope (m) is found
70  by the ratio of the two ranges and the y intersection is 0.
71  // See: https://en.wikipedia.org/wiki/Linear_equation#Slope-intercept_form
72
73  // Since the intersection with the y-axis is at 0, we can ignore it and the equation
74  simplifies to y = mx.
75  // The value of m (slope) can be found using the concept
76  of rise over run. The rise is the change in y value, so 0..11 in our case. The run
77  is the change in x, or 0..1024. So m = 11 /1024.
78  for (int x=0; x<1024; x++)
79  {
80    int y = (int) 11 * x / 1024;
81    Serial.print("y = (int) 11 * x / 1024:
82  x = ");
83    Serial.print(x);
84    Serial.print(", y = ");
85    Serial.println(y);
86
87  }
88
89  // Pause and wait for any kind of input before running again.
90  Serial.println("Send
91  any serial input to run again.");
92  while (!Serial.available());
93  Serial.read();
94}