Using incandescent (filament) 7 segment displays with an Arduino

1// DM134B test program using hardware SPI (or ShiftOut)
2// This displays a seconds counter that counts from 0-999 seconds then resets.
3// If you added a button and relevant code you could use this as a stopwatch.
4// SoftPWM library used to avoid conflicts with timers and SPI when using hardware PWM
5// the SoftPWM library allows the display brightness to be adjusted in software.
6// This circuit will draw approx 600mA at full brightness displaying 8888 (21.5mA per segment) 
7// If high brightness not required either back off using onboard brightness pot or set to max 4 
8// brightness if using software control to adjust brightness through PWM. This will reduce power useage.
9// For example if using for a clock you could automatically dim the display at night.
10
11// 7-segment digits 0-9
12// {Q0, Q1, Q2, Q3, Q4, Q5, Q6, Q7} --> {g, f, e, d, c, b, a, DP} 
13
14#include <SPI.h>
15#include <SoftPWM.h>
16
17int dm134_clock = 13;
18int dm134_latch = 10; // DM134B datasheet says active low but seems to be active high (like a '595)?
19int dm134_data = 11;
20int dm134_OE = 9; // output enable; Active LOW. Can be used to control brightness with PWM.
21
22int brightness = 5; // set display brightness. 1-5 
23int brt = 0; // value for storing reversed PWM percentage
24
25long int cnt = 0; // counter initial value = 0
26unsigned long previousMillis = 0; 
27const long interval = 10;
28
29byte ssddigits[10] = // array without decimal points on
30{
31  B01111110,  // 0
32  B00001100,  // 1
33  B10110110,  // 2
34  B10011110,  // 3
35  B11001100,  // 4
36  B11011010,  // 5
37  B11111010,  // 6
38  B01001110,  // 7
39  B11111110,  // 8
40  B11011110,  // 9
41};
42
43byte ssddigitsDP[10] = // array with decimal points on
44{
45  B01111111,  // 0
46  B00001101,  // 1
47  B10110111,  // 2
48  B10011111,  // 3
49  B11001101,  // 4
50  B11011011,  // 5
51  B11111011,  // 6
52  B01001111,  // 7
53  B11111111,  // 8
54  B11011111,  // 9
55};
56
57void setup() 
58{
59  
60  pinMode (dm134_clock, OUTPUT);
61  pinMode (dm134_latch, OUTPUT);
62  pinMode (dm134_data, OUTPUT);
63  pinMode (dm134_OE,OUTPUT);
64  digitalWrite(dm134_OE,LOW); // enable output of DM134B.
65  setBrt();
66  SoftPWMBegin();
67  SoftPWMSet(9, 0); // init software PWM on pin 9. This pulses the DM134 OE pin on and off to control brightness.
68  SoftPWMSetPercent(9, brt);
69  
70}
71
72void setBrt() // this changes the DM134 brightness logarithmic reversed scale to a more linear one
73
74{
75  if (brightness == 1)
76  brt = 90;
77
78  else if (brightness == 2)
79  brt = 75;
80
81  else if (brightness == 3)
82  brt = 50;
83
84  else if (brightness == 4)
85  brt = 30;
86
87  else if (brightness == 5)
88  brt = 0;
89}
90
91void loop() 
92{
93   unsigned long currentMillis = millis();
94
95  if (currentMillis - previousMillis >= interval) 
96  {
97    previousMillis = currentMillis;
98    cnt++;   
99  }
100   
101   if (cnt == 9999)
102   {
103     cnt = 0;
104   }
105
106   
107   
108   displayNum();
109}
110
111void displayNum()
112{
113
114//long int num = analogRead(0);
115//long int num = 1234;
116long int num = cnt;
117
118// get digit 0
119int dig3 = num % 10; // ones
120// get digit 1
121int dig2 = (num / 10) % 10; // tens
122// get digit 2
123int dig1 = (num / 100) % 10; // hundreds
124// get digit 3
125int dig0 = (num / 1000) % 10; // thousands
126
127SPI.beginTransaction(SPISettings(8000000, LSBFIRST, SPI_MODE0));
128digitalWrite(dm134_latch,LOW);
129SPI.transfer(ssddigits[dig3]); 
130SPI.transfer(ssddigitsDP[dig2]);
131SPI.transfer(ssddigits[dig1]);
132SPI.transfer(ssddigits[dig0]);
133digitalWrite(dm134_latch,HIGH);
134SPI.endTransaction();
135
136/*
137// shift out digits
138digitalWrite(dm134_latch,LOW);
139shiftOut(dm134_data, dm134_clock, LSBFIRST, ssddigits[dig3]); 
140shiftOut(dm134_data, dm134_clock, LSBFIRST, ssddigits[dig2]); 
141shiftOut(dm134_data, dm134_clock, LSBFIRST, ssddigitsDP[dig1]);
142shiftOut(dm134_data, dm134_clock, LSBFIRST, ssddigits[dig0]);
143//shiftOut(dm134_data, dm134_clock, LSBFIRST, B00000001); // DP test
144//shiftOut(dm134_data, dm134_clock, LSBFIRST, B00000001); // DP test
145digitalWrite(dm134_latch,HIGH); 
146
147*/
148
149}