20 Click 3 pin Rotary Encoder on port b pins 2, 3

[Josh Davis]

Hi All. Im using a small Rotary Encoder as a means for a human i/o

I have got my code working but notice that If I twist the Encoder Shaft
pretty fast , I will miss some counts. The encoder is not running any
interrupt as to get to where the code is called the user first has to press
a button on rb.0

Here is a snip of the main routine im using. Basicaly it detects the state of
pins 2, 3 on port b and depending on there state increments, decrements
a variable... Kind of like having 2 switches to do the same job.

It then puts the data on line 2 of a 20X2 chr lcd display.

If any of you have a better way of doing this or perhaps a dedicated encoder routine that might handle what Im trying to do better It would be
most welcome.

My pic is a 16f83 running at 4Mhz

Thanks . Josh.


void encoder(){ // enc1, enc2 are encoder. center pin is ground

LCD_Cmd( CLEAR_DISP );
Lcd_cmd( LCD_LINE1 );
LCD_PutChar("Select TX Freq <- ->");

Lcd_cmd( LCD_LINE2 );
printf(LCD_PutChar, "FREQ: = %Lu Mhz", freq);//Display inital frequency

while (true){ //Loop until break encountered

if (enc2==0)
if (enc2==0) //Test to see if SW2 Went Low. If it did decrement Freq Variable
{
--freq;

if( freq < 200 ) // Bound Lower Freq to no less than 200
freq = 200;

Lcd_cmd( LCD_LINE2 );
printf(LCD_PutChar, "FREQ: = %Lu Mhz", freq);
}

if (enc1==0)
long_delay();
if (enc1==0) //Test to see if SW1 Went Low. If it did increment Freq variable
{
++freq;

if( freq > 250 ) //Bound upper freq to no more than 250
freq = 250;

Lcd_cmd( LCD_LINE2 );
printf(LCD_PutChar, "FREQ: = %Lu Mhz", freq);
}

if (toggle==0)
long_delay(); // de-bounce
if (toggle==0)
break; //If Toggle went Low Return to case3
{
}
}
}

[david smith]

I was working with this a few months ago, using a mechanical rotary switch. After a bunch of time attempting to debounce unsuccessfully, I realized that the two inputs (A,B) are related to the mechanical detent position. In short, swapping the pins made the non-changing one at the right state WRT the transition detent. My routine follows. It inc/dec T1 by the current step size and displays on LCD. Hope it helps

void scanSwitch(){
// ROTARY ENCODER scanner
// better if B transitions are read since B edge is at detent position
// read to vars A,B first; update at end. very smooth now.
// both work when A edges and B levels are checked.

int8 deltaN, k;
int1 A,B;

deltaN = 1; // Number to incr/decr by each loop

while(1){
delay_ms(1);
A = swT2_dn;
B = swT1_dn;

if ((A < Aprev)) { // look at rising edge; check state of B;

if (B == 0 ) {T1 -= deltaN; }
else {T1 += deltaN; }

if (T1 < 0) T1 = Tmax; if (T1>Tmax) T1 = 0; // constrain range (0 - Tmax)

k = 0;
updateDisp(1); // update display line 2
}

if(k++ > 100){
k=0;
updateDisp(0);
writedata(); // write newest values to EEprom
}
Aprev = A;
} // end while
}

[Josh Davis]

Hi David.

I have a question about your code snip.

What is Aprev ?. Im thinking its an int variable

also the

A = swT2_dn;
B = swT1_dn;

are swT1_dn and swT2_dn labels for your switches then your setting int
a and b equal to these so you have 2 variables to use for sampling if the
switches or clicks from the encoder went high or low...


for example before main might look like this.

#BIT swT2_DN = port_b.1
#BIT swT1_DN = port_b.2


void main(void){


Thanks again... Josh.

[david smith]

Since I extracted and edited the routine, I neglected to show variables.

// global stuff...

#BIT swT1_up = PORTB.4
#BIT swT1_dn = PORTC.0

signed int16 D, T1, T2, T3, Dmax, Tmax, Tdist;

int1 Aprev; // holds previous value of A

(You may email me privately for further info.)