Function Generator (Sine, Triangular, Chainsaw, 32 kHz Max)

Delivers excellent signals up to 32.258 kHz (sine wave, etc.), up to 258.064 kHz (rectangular). Output: 0..5V, max res 1 byte.

May 12, 2019

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audio

music

monitoring

Devices & Components

Resistor 221 ohm

Rotary potentiometer (generic)

Resistor 39 Ohm

Resistor 1k ohm

Alphanumeric LCD, 16 x 2

Hardware & Tools

Soldering iron (generic)

Solder Dispenser, Solder-Mate

Project description

Code

Source code for this signal generator

arduino

Just copy & paste it int Arduino IDE, using Arduino version 1.8.9. (tested with Windows only).

1/*  Arduino Starter Kit example    
2  Project Wave Generator
3
4  This sketch is written to have a source to tune music instruments and later get  to the limits...
5
6  Parts required:
7  1x switch
8  1x 220 ohm resistor
9  A resistor network to create an 8 bit DAC to be connected to the port D
10  2x  10 kilohm potentiometer
11  1x 16x2 LCD screen
12  1x piezo
13
14  Created 21.  April 2019
15  by Christian Styger
16
17  Caution: This source code was tailored  to the windows compiler version 1.8.9.
18  If other versions are used, the timing  might not be correct. 
19  >> Use compiler version 1.8.9. (or 1.7.10)!
20*/
21
22//  include the library code for LCD-Display:
23#include <LiquidCrystal.h>
24#define  NOOP(n) __builtin_avr_delay_cycles (n)
25
26const double Pi = 3.1415926535;
27const  byte Clock_Steps_per_us = 1.0 * F_CPU / 1000000; // 1 Clock_Step is 0.0625us = 1/16us  for Arduino Uno with 16 MHz Clock frequency
28
29// initialize the library with  the numbers of the interface pins
30LiquidCrystal lcd(8, 9, 10, 11, 12, 13);
31
32const  byte Pot_Read_Pin = A5;
33const byte Control_Switch_Pin = A4;
34
35// set up  a constant for time delay when a switch was pressed in ms:
36const int Delay_Time  = 500;
37
38// Pins 8,9,10,11,12,13 set to OUTPUT for LCD-display
39const byte  Port_B_Pinrange_LCD     = B00111111;
40
41// Pins A0..A1 set to Input; A2..A5  set for additional DAC channels
42const byte Port_C_Pinrange_Operate = B00111100;
43
44//  Pins A0..A5 set for Input (reading the parameters to set generator)
45const byte  Port_C_Pinrange_Set     = B00000000;
46
47// Pins 7,6,5,4,3,2,1 and 0 [Caution  D0 is usually Rx!!!] set to OUTPUT for 8 bit DAC
48const byte Port_D_Pinrange_Operate  = B11111111; // Port D, being DAC output, having 8 bits (8 bit resolution)
49
50//  Pins 7,6,5,4,3,2,1 set to OUTPUT , and D0 is ready for Rx-funcion to PC
51const  byte Port_D_Pinrange_Set     = B11111110;
52
53int Pot_Value = 1;
54byte T_or_F  = 0;  //This switch indicates if T: Time in us or F: Frequency in Hz is being displayed)
55
56const  byte Generator_Shape_Range = 5;           // 0: Sinewave; 1: Triangular; 2: Chainsaw  down; 3: Chainsaw up; 4: Rectangular; 
57byte Generator_Shape = 4;                       //  Starting shape is sinewave (=(Generator_Shape+1)% Generator_Shape_Range)...
58byte  Generator_Type;                            // Identification of generator to be  used, depending on Tau (length of signal period)...
59const byte Rectangular_Divide  = 8;              // Shorter cycle times possible due to simplicity of rectanguals  signal...
60byte Split, Divide = 1;              
61byte L, k;                                      //  Number of data points that need to be extended by L_Step; k : number of periods  to be mapped in P_D...
62byte Index,s;
63unsigned long NOPs_long; 
64unsigned  long NOPs_Step, NOPs_t, NOPs_Tau = Clock_Steps_per_us*1E6/1000; //  starting value  of Tau in NOPs - corresponds to 1000Hz ....
65unsigned long NOPs_Tau_Max = 4294967295;        //2^32-1 NOPs = 268'435'455.9375us = 4 min 28.435 s is maximum period, using  256 data points to be read out with max delay
66unsigned int  NOPs_Tau_Min = 304;               // Minimum Tau ist 19 us (=16*19 NOPs) for signal shape with minimum  resolution of 16 points / period (sine, triangular,...). 
67byte I_Shift = 0, P_Shift  = 0, Scale = 0;       // Two parameters to ensure that starting data point of a  signal is zero. 
68byte Signal_Shape_Memory[256];                  // Array containing  256 data points to be written to the 1 byte DAC; 
69byte Signal_NOP_Delay_Memory[256];              // Array containing 0 or 255: 0 = No increase by 1 NOP of the data  point; 255 = Prolong delay by 1 NOP.  
70
71byte rectangular (long Time, long  Period) {return  255  *((2*Time/Period)&1);}
72byte sine(long Time, long Period)         {return (512  *(0.5*(1+sin((Time*2.0/Period-0.5)*Pi))))/2;}
73byte chainSawUp(long  Time, long Period)   {return  256.0*(Time-int (Time/Period)*Period)/Period;}
74byte  triangular(long Time, long Period)   {return  256.0*(abs(1-2.0*((Time)-int((Time)/Period)*Period)/Period));}
75
76void  setup() {
77  pinMode(Pot_Read_Pin, INPUT);         // declare pin for potentiometer  as input
78  pinMode(Control_Switch_Pin, INPUT);   // declare the interrupt pin  as an input
79  // setting the ports...
80  DDRB |= Port_B_Pinrange_LCD;          //  Pins 13,12,11,10,9,8 set to OUTPUT for LCD-display
81  DDRC |= Port_C_Pinrange_Set;          // Pins A5,A4,A3,A2 set to INPUT for Additional DAC bits 9-12, Pins A1,  A0 set to INPUT for prgram control
82  DDRD |= Port_D_Pinrange_Set;          //  Pins 7,6,5,4,3,2,1 set to OUTPUT, and D0 is ready for Rx-function to PC
83  lcd.begin(16,  2);
84  lcd.clear();
85}
86
87
88byte PD(byte I) {
89  // Calculates the average  level between Func(NOPs_Tau) and Func(NOPs_Tau + NOPs_Step)....
90  byte Index  = I;
91  byte Level = 0;
92  s = Pot_Value*k/2;
93  while (s > 0) {
94    if  (Index&1 == 1) Level += s;
95    s /= 2;
96    Index /= 2;
97  }
98  long Step;
99  if (L > Level) {Step = NOPs_t+NOPs_Step+1; Signal_NOP_Delay_Memory[I] = 255;}  //     prolonging data point delay by 1 NOP
100  else           {Step = NOPs_t+NOPs_Step  ; Signal_NOP_Delay_Memory[I] = 0  ;}  // not prolonging data point delay by 1  NOP
101  byte P;
102  if      (Generator_Shape == 0) P =  sine       (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift;
103  else if (Generator_Shape == 1) P = ~triangular (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift;
104  else if (Generator_Shape == 2) P = ~chainSawUp (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift+Scale*((16-I)&15);
105  else if (Generator_Shape == 3) P =  chainSawUp (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift+Scale*I;
106  else if (Generator_Shape == 4) P =  rectangular(NOPs_t     ,  NOPs_Tau/Divide/k);
107  NOPs_t = Step;
108  Signal_Shape_Memory[I] = P;
109  return (P);
110}
111
112void  Show_Parameter ()
113  {
114    lcd.setCursor (0, 1);
115    if (T_or_F == 0) {
116      lcd.print ("T:              ");
117      lcd.setCursor (3, 1);
118      lcd.print  (1.0*NOPs_Tau/Clock_Steps_per_us, 4);
119      lcd.setCursor (14, 1);
120      lcd.print  ("us");
121    } else {
122      lcd.print ("F:              ");
123      lcd.setCursor  (3, 1);
124      lcd.print (1000000.0/NOPs_Tau*Clock_Steps_per_us, 4);
125      lcd.setCursor  (14, 1);
126      lcd.print ("Hz");
127    } 
128  }
129
130void loop() {
131  
132  // Select the generator type (sine, rectangular, triangular, etc.), using  potentiometer to select & button to confirm...
133  lcd.setCursor(0, 0);
134  lcd.print  ("Gen");      
135  while (digitalRead(Control_Switch_Pin) == HIGH) {
136    if  (Pot_Value != 0) {
137      if (Pot_Value > 0) s = 1; else s = Generator_Shape_Range-1;  
138      Generator_Shape = (Generator_Shape+s)%Generator_Shape_Range;
139      lcd.setCursor(4,  0);  
140      if      (Generator_Shape == 0) lcd.print ("Sine Wave  ");
141      else  if (Generator_Shape == 1) lcd.print ("Triangular ");
142      else if (Generator_Shape  == 2) lcd.print ("Chainsaw Dn");
143      else if (Generator_Shape == 3) lcd.print  ("Chainsaw Up");
144      else if (Generator_Shape == 4) lcd.print ("Rectangular");
145    }
146    delay (2*Delay_Time);  
147    Pot_Value = map(analogRead(Pot_Read_Pin),  0, 1023, -5, +5);      
148  }
149  if (Generator_Shape == 4) NOPs_Tau_Min /= Rectangular_Divide;
150
151
152  // Set display to either Frequency or Time, using potentiometer to switch & button  to confirm...
153  lcd.setCursor(0, 0);
154  lcd.print ("F/T");
155  Show_Parameter  ();
156  while (digitalRead(Control_Switch_Pin) == LOW);
157  delay (Delay_Time);  
158  while (digitalRead(Control_Switch_Pin) == HIGH) {
159    if (Pot_Value !=  0) {
160      T_or_F = ++T_or_F&1;
161      Show_Parameter ();
162    }
163    delay  (Delay_Time);  
164    Pot_Value = map(analogRead(Pot_Read_Pin), 0, 1023, -12, +12);      
165  }
166
167
168  // Set the Frequency or Time (period length), using potentiometer  to sselect & button to confirm...
169  lcd.setCursor(0, 0);
170  lcd.print ("Set");
171  while (digitalRead(Control_Switch_Pin) == LOW);
172  delay (Delay_Time);  
173  while (digitalRead(Control_Switch_Pin) == HIGH) {
174    Pot_Value = map(analogRead(Pot_Read_Pin),  0, 1023, -12, +12);
175    if (T_or_F == 1) Pot_Value = -Pot_Value; 
176    NOPs_Step  = abs(Pot_Value*Pot_Value*Pot_Value);
177    if (Pot_Value != 0) {
178      s =  1;
179      if      (Pot_Value ==  12) {NOPs_Step =  NOPs_Tau;   s = 2*Delay_Time;}  
180      else if (Pot_Value == -12) {NOPs_Step =  NOPs_Tau/2; s = 2*Delay_Time;}
181      if (Pot_Value < 0)
182        if (NOPs_Tau-NOPs_Tau_Min >= NOPs_Step) 
183          NOPs_Tau -= NOPs_Step; 
184        else
185          NOPs_Tau = NOPs_Tau_Min;     
186      else   
187        if (NOPs_Tau_Max-NOPs_Tau >= NOPs_Step) 
188          NOPs_Tau  += NOPs_Step; 
189        else
190          NOPs_Tau = NOPs_Tau_Max;  
191      Show_Parameter  ();
192      delay (Delay_Time/(Pot_Value*Pot_Value)+s);
193    }
194  }
195  if  ((Generator_Shape == 4) && (NOPs_Tau < 16000)) {Divide = Rectangular_Divide; NOPs_Tau  *= Rectangular_Divide;} 
196
197// Selection of generator_Type...
198  if      (NOPs_Tau  >= 4864) Pot_Value=256;  //304 us: 256 * 19 NOPs = 4864 NOPs  (/16 = 304 us =  3.289  kHz )   
199  else if (NOPs_Tau >= 2432) Pot_Value=128;  //152 us: 128 * 19 NOPs  = 2432 NOPs  (/16 = 152 us =  6.578 kHz )
200  else if (NOPs_Tau >= 1216) Pot_Value=  64;  // 76 us:  64 * 19 NOPs = 1216 NOPs  (/16 =  76 us = 13.157 kHz )
201  else  if (NOPs_Tau >=  608) Pot_Value= 32;  // 38 us:  32 * 19 NOPs =  608 NOPs  (/16  =  38 us = 26.315 kHz )
202  else    {                  Pot_Value= 16;  // 19 us:  16 * 19 NOPs =  304 NOPs  (/16 =  19 us = 52.631 kHz)  
203                             Scale=1;}       // Scale = 1 increases amplitude of Chainsaw up and down at low resolution.  i.e. 16 data points... 
204
205  NOPs_Step = NOPs_Tau/Pot_Value;            //38...(4'294'967'296-1)/256  [16'777'215] NOPs_Tau_max: 268.435456 sec
206  L = NOPs_Tau%Pot_Value;                    //L  (NOPs_Tau_ long_max): 255
207  k = 256/Pot_Value;
208
209  if      (NOPs_Step >=  31) {Generator_Type =  31; Split = (NOPs_Step-31)%6; NOPs_long = (NOPs_Step-31)/6;  }  
210  else if (NOPs_Step >= 25) {Generator_Type =  25; Split =  NOPs_Step-25;}
211  else if (NOPs_Step >= 22) {Generator_Type =  22; Split =  NOPs_Step-22;}
212  else                      {Generator_Type = NOPs_Step;}
213  
214  // Setting up parameters  to calculate shape...
215  NOPs_Tau *= k;
216  L *= k;
217  
218  // Adjust all  shapes such theat zero value is starting point (PD_0 = 0)... 
219  if (Generator_Shape  <= 3) I_Shift=1;
220  NOPs_t = NOPs_Tau-I_Shift*(NOPs_Step);   
221  
222  P_Shift  = PD(0);
223  Signal_Shape_Memory[0] = 0;
224
225  // Calculating & loading the  signal shape into array P_D... 
226  Index=0;
227  while (Index < 255) Signal_Shape_Memory[++Index]  = PD(Index);    
228
229  // Starting the appropriate generator according to settings...
230  lcd.setCursor(0, 0);
231  lcd.print ("Run");
232
233  noInterrupts();
234  DDRD  |= Port_D_Pinrange_Operate;      // Pins 7,6,5,4,3,2,1,0
235  
236  switch (Generator_Type)  {
237    case 19: Loop_256_19       (); break;  
238    case 20: Loop_256_20       ();  break;
239    case 21: Loop_256_21       (); break;
240    case 22: Loop_256_22_24    (); break;
241    case 25: Loop_256_25_33    (); break;
242    case 31: Loop_256_31_36_6n  (); break;
243  }
244}
245
246void Loop_256_31_36_6n ()
247{
248  unsigned long  NOPs_6x = long (abs(NOPs_long));
249  byte Shift = Split+2;
250  byte Index = 0;
251  NOPs_long = NOPs_long+100;   // This line is necessary to get the timing right  for NOPSx_6x = 0, 1, 2... (I don't know why...)
252  unsigned long Cycle;
253  
254  while (true) {
255    ++Index; 
256    PORTD = Signal_Shape_Memory[Index]; 
257    Cycle = NOPs_6x; 
258    while (--Cycle<~0) NOOP(0); 
259    if (Shift&1) NOOP(2);  
260    if (~Shift&4); 
261      else if (Shift&2) NOOP(3); 
262        else NOOP(0);  
263    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
264  }
265}
266
267void  Loop_256_25_33 ()
268{
269  byte Shift = ((Split)/3)*4+5+((Split)%3);
270  byte  Index = 0;
271  while (true) {
272    ++Index;
273    PORTD = Signal_Shape_Memory[Index];
274    if (~Shift&2);
275    else if (Shift&1) NOOP(2);
276      else NOOP(0); 
277    if (~Shift&8);
278      else if (Shift&4) NOOP(5);
279      else NOOP(1);
280      if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
281  }
282}
283
284void  Loop_256_22_24 ()
285{
286  byte Shift = Split+1;
287  byte Index = 0;
288  while  (true) {
289    ++Index;
290    PORTD = Signal_Shape_Memory[Index];
291    if (~Shift&2)  NOOP(1); 
292      else {NOOP(1); if (Shift&1) NOOP(2);  //This is the correct line  for compiler Arduino 1.8.9  
293        else NOOP(0);}                      //This  is the correct line for compiler Arduino 1.8.9  
294//      else if (Shift&1) NOOP(2);          //This is the correct line for compiler Arduino 1.7.10 
295//        else  NOOP(0);                     //This is the correct line for compiler Arduino 1.7.10  
296    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
297  }
298}
299
300void  Loop_256_21 ()
301{
302  byte Index = 0;
303  NOPs_long = NOPs_long+100;   // This  line is necessary to get the timing right for NOPSx_6x = 0, 1, 2... (I don't know  why...)
304  while (true) {
305    ++Index;
306    PORTD = Signal_Shape_Memory[Index];
307    NOOP(2);
308    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
309  }
310}
311
312void Loop_256_20 ()
313{
314  byte Index = 0;
315  while (true)  {
316    NOOP(1);
317    ++Index;
318    NOOP(1);
319    PORTD = Signal_Shape_Memory[Index];
320    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
321  }
322}
323
324void  Loop_256_19 ()
325{
326  byte Index = 0;
327  while (true) {
328    ++Index;
329    PORTD = Signal_Shape_Memory[Index];
330  if (Signal_NOP_Delay_Memory[Index])  NOOP(3); else NOOP(1);
331  }
332}
333

/*  Arduino Starter Kit example    
  Project Wave Generator

  This sketch is written to have a source to tune music instruments and later get  to the limits...

  Parts required:
  1x switch
  1x 220 ohm resistor
  A resistor network to create an 8 bit DAC to be connected to the port D
  2x  10 kilohm potentiometer
  1x 16x2 LCD screen
  1x piezo

  Created 21.  April 2019
  by Christian Styger

  Caution: This source code was tailored  to the windows compiler version 1.8.9.
  If other versions are used, the timing  might not be correct. 
  >> Use compiler version 1.8.9. (or 1.7.10)!
*/

//  include the library code for LCD-Display:
#include <LiquidCrystal.h>
#define  NOOP(n) __builtin_avr_delay_cycles (n)

const double Pi = 3.1415926535;
const  byte Clock_Steps_per_us = 1.0 * F_CPU / 1000000; // 1 Clock_Step is 0.0625us = 1/16us  for Arduino Uno with 16 MHz Clock frequency

// initialize the library with  the numbers of the interface pins
LiquidCrystal lcd(8, 9, 10, 11, 12, 13);

const  byte Pot_Read_Pin = A5;
const byte Control_Switch_Pin = A4;

// set up  a constant for time delay when a switch was pressed in ms:
const int Delay_Time  = 500;

// Pins 8,9,10,11,12,13 set to OUTPUT for LCD-display
const byte  Port_B_Pinrange_LCD     = B00111111;

// Pins A0..A1 set to Input; A2..A5  set for additional DAC channels
const byte Port_C_Pinrange_Operate = B00111100;

//  Pins A0..A5 set for Input (reading the parameters to set generator)
const byte  Port_C_Pinrange_Set     = B00000000;

// Pins 7,6,5,4,3,2,1 and 0 [Caution  D0 is usually Rx!!!] set to OUTPUT for 8 bit DAC
const byte Port_D_Pinrange_Operate  = B11111111; // Port D, being DAC output, having 8 bits (8 bit resolution)

//  Pins 7,6,5,4,3,2,1 set to OUTPUT , and D0 is ready for Rx-funcion to PC
const  byte Port_D_Pinrange_Set     = B11111110;

int Pot_Value = 1;
byte T_or_F  = 0;  //This switch indicates if T: Time in us or F: Frequency in Hz is being displayed)

const  byte Generator_Shape_Range = 5;           // 0: Sinewave; 1: Triangular; 2: Chainsaw  down; 3: Chainsaw up; 4: Rectangular; 
byte Generator_Shape = 4;                       //  Starting shape is sinewave (=(Generator_Shape+1)% Generator_Shape_Range)...
byte  Generator_Type;                            // Identification of generator to be  used, depending on Tau (length of signal period)...
const byte Rectangular_Divide  = 8;              // Shorter cycle times possible due to simplicity of rectanguals  signal...
byte Split, Divide = 1;              
byte L, k;                                      //  Number of data points that need to be extended by L_Step; k : number of periods  to be mapped in P_D...
byte Index,s;
unsigned long NOPs_long; 
unsigned  long NOPs_Step, NOPs_t, NOPs_Tau = Clock_Steps_per_us*1E6/1000; //  starting value  of Tau in NOPs - corresponds to 1000Hz ....
unsigned long NOPs_Tau_Max = 4294967295;        //2^32-1 NOPs = 268'435'455.9375us = 4 min 28.435 s is maximum period, using  256 data points to be read out with max delay
unsigned int  NOPs_Tau_Min = 304;               // Minimum Tau ist 19 us (=16*19 NOPs) for signal shape with minimum  resolution of 16 points / period (sine, triangular,...). 
byte I_Shift = 0, P_Shift  = 0, Scale = 0;       // Two parameters to ensure that starting data point of a  signal is zero. 
byte Signal_Shape_Memory[256];                  // Array containing  256 data points to be written to the 1 byte DAC; 
byte Signal_NOP_Delay_Memory[256];              // Array containing 0 or 255: 0 = No increase by 1 NOP of the data  point; 255 = Prolong delay by 1 NOP.  

byte rectangular (long Time, long  Period) {return  255  *((2*Time/Period)&1);}
byte sine(long Time, long Period)         {return (512  *(0.5*(1+sin((Time*2.0/Period-0.5)*Pi))))/2;}
byte chainSawUp(long  Time, long Period)   {return  256.0*(Time-int (Time/Period)*Period)/Period;}
byte  triangular(long Time, long Period)   {return  256.0*(abs(1-2.0*((Time)-int((Time)/Period)*Period)/Period));}

void  setup() {
  pinMode(Pot_Read_Pin, INPUT);         // declare pin for potentiometer  as input
  pinMode(Control_Switch_Pin, INPUT);   // declare the interrupt pin  as an input
  // setting the ports...
  DDRB |= Port_B_Pinrange_LCD;          //  Pins 13,12,11,10,9,8 set to OUTPUT for LCD-display
  DDRC |= Port_C_Pinrange_Set;          // Pins A5,A4,A3,A2 set to INPUT for Additional DAC bits 9-12, Pins A1,  A0 set to INPUT for prgram control
  DDRD |= Port_D_Pinrange_Set;          //  Pins 7,6,5,4,3,2,1 set to OUTPUT, and D0 is ready for Rx-function to PC
  lcd.begin(16,  2);
  lcd.clear();
}


byte PD(byte I) {
  // Calculates the average  level between Func(NOPs_Tau) and Func(NOPs_Tau + NOPs_Step)....
  byte Index  = I;
  byte Level = 0;
  s = Pot_Value*k/2;
  while (s > 0) {
    if  (Index&1 == 1) Level += s;
    s /= 2;
    Index /= 2;
  }
  long Step;
  if (L > Level) {Step = NOPs_t+NOPs_Step+1; Signal_NOP_Delay_Memory[I] = 255;}  //     prolonging data point delay by 1 NOP
  else           {Step = NOPs_t+NOPs_Step  ; Signal_NOP_Delay_Memory[I] = 0  ;}  // not prolonging data point delay by 1  NOP
  byte P;
  if      (Generator_Shape == 0) P =  sine       (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift;
  else if (Generator_Shape == 1) P = ~triangular (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift;
  else if (Generator_Shape == 2) P = ~chainSawUp (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift+Scale*((16-I)&15);
  else if (Generator_Shape == 3) P =  chainSawUp (NOPs_t+Step,2*NOPs_Tau/k)-P_Shift+Scale*I;
  else if (Generator_Shape == 4) P =  rectangular(NOPs_t     ,  NOPs_Tau/Divide/k);
  NOPs_t = Step;
  Signal_Shape_Memory[I] = P;
  return (P);
}

void  Show_Parameter ()
  {
    lcd.setCursor (0, 1);
    if (T_or_F == 0) {
      lcd.print ("T:              ");
      lcd.setCursor (3, 1);
      lcd.print  (1.0*NOPs_Tau/Clock_Steps_per_us, 4);
      lcd.setCursor (14, 1);
      lcd.print  ("us");
    } else {
      lcd.print ("F:              ");
      lcd.setCursor  (3, 1);
      lcd.print (1000000.0/NOPs_Tau*Clock_Steps_per_us, 4);
      lcd.setCursor  (14, 1);
      lcd.print ("Hz");
    } 
  }

void loop() {
  
  // Select the generator type (sine, rectangular, triangular, etc.), using  potentiometer to select & button to confirm...
  lcd.setCursor(0, 0);
  lcd.print  ("Gen");      
  while (digitalRead(Control_Switch_Pin) == HIGH) {
    if  (Pot_Value != 0) {
      if (Pot_Value > 0) s = 1; else s = Generator_Shape_Range-1;  
      Generator_Shape = (Generator_Shape+s)%Generator_Shape_Range;
      lcd.setCursor(4,  0);  
      if      (Generator_Shape == 0) lcd.print ("Sine Wave  ");
      else  if (Generator_Shape == 1) lcd.print ("Triangular ");
      else if (Generator_Shape  == 2) lcd.print ("Chainsaw Dn");
      else if (Generator_Shape == 3) lcd.print  ("Chainsaw Up");
      else if (Generator_Shape == 4) lcd.print ("Rectangular");
    }
    delay (2*Delay_Time);  
    Pot_Value = map(analogRead(Pot_Read_Pin),  0, 1023, -5, +5);      
  }
  if (Generator_Shape == 4) NOPs_Tau_Min /= Rectangular_Divide;


  // Set display to either Frequency or Time, using potentiometer to switch & button  to confirm...
  lcd.setCursor(0, 0);
  lcd.print ("F/T");
  Show_Parameter  ();
  while (digitalRead(Control_Switch_Pin) == LOW);
  delay (Delay_Time);  
  while (digitalRead(Control_Switch_Pin) == HIGH) {
    if (Pot_Value !=  0) {
      T_or_F = ++T_or_F&1;
      Show_Parameter ();
    }
    delay  (Delay_Time);  
    Pot_Value = map(analogRead(Pot_Read_Pin), 0, 1023, -12, +12);      
  }


  // Set the Frequency or Time (period length), using potentiometer  to sselect & button to confirm...
  lcd.setCursor(0, 0);
  lcd.print ("Set");
  while (digitalRead(Control_Switch_Pin) == LOW);
  delay (Delay_Time);  
  while (digitalRead(Control_Switch_Pin) == HIGH) {
    Pot_Value = map(analogRead(Pot_Read_Pin),  0, 1023, -12, +12);
    if (T_or_F == 1) Pot_Value = -Pot_Value; 
    NOPs_Step  = abs(Pot_Value*Pot_Value*Pot_Value);
    if (Pot_Value != 0) {
      s =  1;
      if      (Pot_Value ==  12) {NOPs_Step =  NOPs_Tau;   s = 2*Delay_Time;}  
      else if (Pot_Value == -12) {NOPs_Step =  NOPs_Tau/2; s = 2*Delay_Time;}
      if (Pot_Value < 0)
        if (NOPs_Tau-NOPs_Tau_Min >= NOPs_Step) 
          NOPs_Tau -= NOPs_Step; 
        else
          NOPs_Tau = NOPs_Tau_Min;     
      else   
        if (NOPs_Tau_Max-NOPs_Tau >= NOPs_Step) 
          NOPs_Tau  += NOPs_Step; 
        else
          NOPs_Tau = NOPs_Tau_Max;  
      Show_Parameter  ();
      delay (Delay_Time/(Pot_Value*Pot_Value)+s);
    }
  }
  if  ((Generator_Shape == 4) && (NOPs_Tau < 16000)) {Divide = Rectangular_Divide; NOPs_Tau  *= Rectangular_Divide;} 

// Selection of generator_Type...
  if      (NOPs_Tau  >= 4864) Pot_Value=256;  //304 us: 256 * 19 NOPs = 4864 NOPs  (/16 = 304 us =  3.289  kHz )   
  else if (NOPs_Tau >= 2432) Pot_Value=128;  //152 us: 128 * 19 NOPs  = 2432 NOPs  (/16 = 152 us =  6.578 kHz )
  else if (NOPs_Tau >= 1216) Pot_Value=  64;  // 76 us:  64 * 19 NOPs = 1216 NOPs  (/16 =  76 us = 13.157 kHz )
  else  if (NOPs_Tau >=  608) Pot_Value= 32;  // 38 us:  32 * 19 NOPs =  608 NOPs  (/16  =  38 us = 26.315 kHz )
  else    {                  Pot_Value= 16;  // 19 us:  16 * 19 NOPs =  304 NOPs  (/16 =  19 us = 52.631 kHz)  
                             Scale=1;}       // Scale = 1 increases amplitude of Chainsaw up and down at low resolution.  i.e. 16 data points... 

  NOPs_Step = NOPs_Tau/Pot_Value;            //38...(4'294'967'296-1)/256  [16'777'215] NOPs_Tau_max: 268.435456 sec
  L = NOPs_Tau%Pot_Value;                    //L  (NOPs_Tau_ long_max): 255
  k = 256/Pot_Value;

  if      (NOPs_Step >=  31) {Generator_Type =  31; Split = (NOPs_Step-31)%6; NOPs_long = (NOPs_Step-31)/6;  }  
  else if (NOPs_Step >= 25) {Generator_Type =  25; Split =  NOPs_Step-25;}
  else if (NOPs_Step >= 22) {Generator_Type =  22; Split =  NOPs_Step-22;}
  else                      {Generator_Type = NOPs_Step;}
  
  // Setting up parameters  to calculate shape...
  NOPs_Tau *= k;
  L *= k;
  
  // Adjust all  shapes such theat zero value is starting point (PD_0 = 0)... 
  if (Generator_Shape  <= 3) I_Shift=1;
  NOPs_t = NOPs_Tau-I_Shift*(NOPs_Step);   
  
  P_Shift  = PD(0);
  Signal_Shape_Memory[0] = 0;

  // Calculating & loading the  signal shape into array P_D... 
  Index=0;
  while (Index < 255) Signal_Shape_Memory[++Index]  = PD(Index);    

  // Starting the appropriate generator according to settings...
  lcd.setCursor(0, 0);
  lcd.print ("Run");

  noInterrupts();
  DDRD  |= Port_D_Pinrange_Operate;      // Pins 7,6,5,4,3,2,1,0
  
  switch (Generator_Type)  {
    case 19: Loop_256_19       (); break;  
    case 20: Loop_256_20       ();  break;
    case 21: Loop_256_21       (); break;
    case 22: Loop_256_22_24    (); break;
    case 25: Loop_256_25_33    (); break;
    case 31: Loop_256_31_36_6n  (); break;
  }
}

void Loop_256_31_36_6n ()
{
  unsigned long  NOPs_6x = long (abs(NOPs_long));
  byte Shift = Split+2;
  byte Index = 0;
  NOPs_long = NOPs_long+100;   // This line is necessary to get the timing right  for NOPSx_6x = 0, 1, 2... (I don't know why...)
  unsigned long Cycle;
  
  while (true) {
    ++Index; 
    PORTD = Signal_Shape_Memory[Index]; 
    Cycle = NOPs_6x; 
    while (--Cycle<~0) NOOP(0); 
    if (Shift&1) NOOP(2);  
    if (~Shift&4); 
      else if (Shift&2) NOOP(3); 
        else NOOP(0);  
    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
  }
}

void  Loop_256_25_33 ()
{
  byte Shift = ((Split)/3)*4+5+((Split)%3);
  byte  Index = 0;
  while (true) {
    ++Index;
    PORTD = Signal_Shape_Memory[Index];
    if (~Shift&2);
    else if (Shift&1) NOOP(2);
      else NOOP(0); 
    if (~Shift&8);
      else if (Shift&4) NOOP(5);
      else NOOP(1);
      if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
  }
}

void  Loop_256_22_24 ()
{
  byte Shift = Split+1;
  byte Index = 0;
  while  (true) {
    ++Index;
    PORTD = Signal_Shape_Memory[Index];
    if (~Shift&2)  NOOP(1); 
      else {NOOP(1); if (Shift&1) NOOP(2);  //This is the correct line  for compiler Arduino 1.8.9  
        else NOOP(0);}                      //This  is the correct line for compiler Arduino 1.8.9  
//      else if (Shift&1) NOOP(2);          //This is the correct line for compiler Arduino 1.7.10 
//        else  NOOP(0);                     //This is the correct line for compiler Arduino 1.7.10  
    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
  }
}

void  Loop_256_21 ()
{
  byte Index = 0;
  NOPs_long = NOPs_long+100;   // This  line is necessary to get the timing right for NOPSx_6x = 0, 1, 2... (I don't know  why...)
  while (true) {
    ++Index;
    PORTD = Signal_Shape_Memory[Index];
    NOOP(2);
    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
  }
}

void Loop_256_20 ()
{
  byte Index = 0;
  while (true)  {
    NOOP(1);
    ++Index;
    NOOP(1);
    PORTD = Signal_Shape_Memory[Index];
    if (Signal_NOP_Delay_Memory[Index]) NOOP(3); else NOOP(1);
  }
}

void  Loop_256_19 ()
{
  byte Index = 0;
  while (true) {
    ++Index;
    PORTD = Signal_Shape_Memory[Index];
  if (Signal_NOP_Delay_Memory[Index])  NOOP(3); else NOOP(1);
  }
}

Downloadable files

Signal Generator (Wiring)

Potentiometer left: Brightness of LCD-display Button: Select signal shape / set display in Hz or us / start generator Potentiometer right: Select frequency / Period Rest button: stop & restart generator

Signal Generator (Wiring)

Documentation

Scheme of Signal Generator

Scheme

Scheme of Signal Generator

Scheme

Scheme of Signal Generator

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