Here's the code i managed to write, but the problem is, that i am not so sure it will work, so i decided to post it here for you to see it and tell me what you think. For now only the speed of frequency changing can be set by "s", future plan is to make code that will allow me to control the speed of frequency alternation (form 33-61Hz) and min and max output frequency (to set higher f_min than 33Hz and lower f_max than 66Hz) by reading analog values. That's next, I am in no hurry...
Please comment - suggestions are more than wellcome!
/* based on code by srnka
Generating of PWM signals for single phase inverter circuit
generating of sine signals with freq from 33 Hz to 61 Hz
output values: PWM signals on 2 PWM outputs: one inverted and one non-inverted
*/
int i; //i...for cycle
int j=64; //for setting the correct number of steps for the selected frequency (initial is the nr. of samples at 61Hz)
int z=0; //for selecting the correct value from the sinetable
int x=0; //frequency selector - setting initial freq to 61 Hz
int y=0; //setting of loop counter
int s=30; //this value is the speed of frequency changing - later it could be controlled by a variable resistor connected to analog input
float phase; // For calculating value of phase
//setting of sin table for half-period of 8 frequencies
// steps frequency
//sin1 64 61,03515625
//sin2 70 55,80357143
//sin3 78 50,08012821
//sin4 86 45,42151163
//sin5 94 41,55585106
//sin6 102 38,29656863
//sin7 110 35,51136364
//sin8 118 33,10381356
//======================:.-"-.: S I N E T A B L E :.-"-.:====================================
//values are calculated from sinus values and amplidude is corrected based on tests
int sinus[]= {127, 133, 140, 146, 152, 158, 164, 170, 176, 182, 188, 193, 199, 204, 209, 213,
218, 222, 226, 230, 234, 237, 240, 243, 245, 247, 249, 251, 252, 253, 254, 254, 254, 254, 253,
252, 251, 249, 247, 245, 243, 240, 237, 234, 230, 226, 222, 218, 213, 209, 204, 199, 193, 188,
182, 176, 170, 164, 158, 152, 146, 140, 133, 127,
127, 132, 138, 143, 148, 153, 158, 163, 168, 173, 178, 183, 187, 192, 196, 200, 204, 208, 212,
215, 219, 222, 225, 227, 230, 232, 234, 236, 238, 239, 241, 242, 242, 243, 243, 243, 243, 242,
242, 241, 239, 238, 236, 234, 232, 230, 227, 225, 222, 219, 215, 212, 208, 204, 200, 196, 192,
187, 183, 178, 173, 168, 163, 158, 153, 148, 143, 138, 132, 127,
127, 131, 136, 140, 144, 149, 153, 157, 161, 165, 169, 173, 177, 181, 185, 188, 192, 195, 199,
202, 205, 208, 211, 213, 216, 218, 220, 222, 224, 226, 228, 229, 230, 231, 232, 233, 233, 234,
234, 234, 234, 233, 233, 232, 231, 230, 229, 228, 226, 224, 222, 220, 218, 216, 213, 211, 208,
205, 202, 199, 195, 192, 188, 185, 181, 177, 173, 169, 165, 161, 157, 153, 149, 144, 140, 136,
131, 127,
127, 131, 134, 138, 142, 145, 149, 152, 156, 159, 163, 166, 169, 173, 176, 179, 182, 185, 188,
191, 194, 196, 199, 201, 204, 206, 208, 210, 212, 214, 216, 217, 219, 220, 221, 222, 223, 224,
225, 225, 226, 226, 226, 226, 226, 226, 225, 225, 224, 223, 222, 221, 220, 219, 217, 216, 214,
212, 210, 208, 206, 204, 201, 199, 196, 194, 191, 188, 185, 182, 179, 176, 173, 169, 166, 163,
159, 156, 152, 149, 145, 142, 138, 134, 131, 127,
127, 130, 133, 136, 139, 142, 145, 148, 151, 154, 157, 160, 163, 166, 168, 171, 174, 176, 179,
181, 184, 186, 189, 191, 193, 195, 197, 199, 201, 203, 204, 206, 207, 209, 210, 211, 212, 213,
214, 215, 216, 216, 217, 217, 218, 218, 218, 218, 218, 218, 217, 217, 216, 216, 215, 214, 213,
212, 211, 210, 209, 207, 206, 204, 203, 201, 199, 197, 195, 193, 191, 189, 186, 184, 181, 179,
176, 174, 171, 168, 166, 163, 160, 157, 154, 151, 148, 145, 142, 139, 136, 133, 130, 127,
127, 130, 132, 135, 137, 140, 142, 145, 147, 150, 152, 155, 157, 160, 162, 164, 167, 169, 171,
173, 175, 177, 179, 181, 183, 185, 187, 189, 190, 192, 194, 195, 197, 198, 199, 201, 202, 203,
204, 205, 206, 206, 207, 208, 208, 209, 209, 210, 210, 210, 210, 210, 210, 210, 210, 209, 209,
208, 208, 207, 206, 206, 205, 204, 203, 202, 201, 199, 198, 197, 195, 194, 192, 190, 189, 187,
185, 183, 181, 179, 177, 175, 173, 171, 169, 167, 164, 162, 160, 157, 155, 152, 150, 147, 145,
142, 140, 137, 135, 132, 130, 127,
127, 129, 131, 133, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160, 162, 164,
166, 168, 170, 171, 173, 175, 176, 178, 180, 181, 183, 184, 185, 187, 188, 189, 190, 192, 193,
194, 195, 196, 196, 197, 198, 199, 199, 200, 200, 201, 201, 201, 202, 202, 202, 202, 202, 202,
202, 202, 201, 201, 201, 200, 200, 199, 199, 198, 197, 196, 196, 195, 194, 193, 192, 190, 189,
188, 187, 185, 184, 183, 181, 180, 178, 176, 175, 173, 171, 170, 168, 166, 164, 162, 160, 158,
156, 154, 152, 150, 148, 146, 144, 142, 140, 138, 136, 133, 131, 129, 127,
127, 129, 131, 132, 134, 136, 138, 140, 141, 143, 145, 147, 148, 150, 152, 153, 155, 157, 158,
160, 161, 163, 164, 166, 167, 169, 170, 171, 173, 174, 175, 177, 178, 179, 180, 181, 182, 183,
184, 185, 186, 187, 188, 188, 189, 190, 190, 191, 191, 192, 192, 193, 193, 193, 194, 194, 194,
194, 194, 194, 194, 194, 194, 194, 193, 193, 193, 192, 192, 191, 191, 190, 190, 189, 188, 188,
187, 186, 185, 184, 183, 182, 181, 180, 179, 178, 177, 175, 174, 173, 171, 170, 169, 167, 166,
164, 163, 161, 160, 158, 157, 155, 153, 152, 150, 148, 147, 145, 143, 141, 140, 138, 136, 134,
132, 131, 129, 127};
//14 steps of frequency ramping (actually just 8 different freq. in loop)
int fbase[]={64,70,78,86,94,102,110,118,110,102,94,86,78,70};
//======================:.-"-.: S E T U P :.-"-.:============================================
void setup()
{
//=====setting of timer0 for fast PWM method====
//frequency PWM is fosc/(8*256) (by 16MHz oscil. = 7812,5)
//timer 0, 8-bit timer, pins 5,6(+) 128us
TCCR0A=0b10110011; // generate inverted PWM signals in output
TCCR0B=0b00000010; // set of source of clock signal + prescaller
//setting of PWM ports 5 and 6 to output (one is inverted - frequency is the same all the time)
pinMode(5,OUTPUT);
pinMode(6,OUTPUT);
}
//======================:.-"-.: M A I N L O O P :.-"-.:============================================
void loop()
{
//when "2*s" number of loops are made, the frequency is changed
//(2*s to get whole sine wave - 360deg, no matter what the value of "s" is,
//since j is the number of steps in half of sine period (at startup it is set to 64, so the infinite loop can) start
if(y==2*s*j) //check if some frequency has been looped for 2*s times (since j is a number of steps in 1/2 period
{ x=x+1; //here the frequency change is done with "x" (initial value is 0!)
if(x==14){ //if x is higher than 13 i.e. when x==14 it needs to be set to 0 again
x=0;}
}
j=fbase[x]; //setting the freq. to the selected one / first the x=0, so j=64 (frequency is 61 Hz)
//change of polarity
TCCR0A = TCCR0A ^ 0b01010000;
//cycle for half period
for(i=0; i<j;i++)
{
//setting the correct "z" for the selected frequency
if(j==64){ // 61Hz
z=i;
}
if(j==70){ // 55Hz
z=i+64; //+64
}
if(j==78){
z=i+134; //70+64 // 50Hz
}
if(j==86){
z=i+212; //78+70+64 // 45Hz
}
if(j==94){
z=i+298; //86+78+70+64 // 42Hz
}
if(j==102){
z=i+392; //94+86+78+70+64 // 38Hz
}
if(j==110){
z=i+494; //102+94+86+78+70+64 // 35Hz
}
if(j==118){
z=i+604; //110+102+94+86+78+70+64 //33Hz
}
//generating of value OCR0x, but output frequency is the same, since they are toggled outputs
//(it's just that when one sine wave raises the other decreases)
phase=sinus[z];
OCR0A=byte(phase);
OCR0B=byte(phase);
}
//******************************************************
y=y++; //loop counter
}
