Driving DC w/ PWM

[o_wan]

hi all,

Since my PIC16F877A got 2 PWM only, is that possible to drive DC w/o PWM, can I use generate pulse on & off code to replace PWM like below and w/ h-bridge circuit?

Anyone did that b4?

#include <16f877A.h> /*include standard functions of our PIC chip*/
#fuses XT,NOLVP,NOWDT
#use delay(clock=4000000)

void MOVE(int on, int off)
{
{output_bit(PIN_A2,1); output_bit(PIN_A3,0);}
{output_bit(PIN_A1,1); output_bit(PIN_A0,0);}
delay_ms(on);
{output_bit(PIN_A2,0); output_bit(PIN_A3,0);}
{output_bit(PIN_A1,0); output_bit(PIN_A0,0);}
delay_ms(off);
}

main(){
int t;

while(1){
for(t=0;t<100;t++) MOVE(3,10);
for(t=0;t<30;t++) MOVE(10,10);
}
}

[SherpaDoug]

That should work, but I would just set up an XOR mask for port A so I could change all four outputs with a single instruction. You can load the port with a word that shuts off all the switches to let the motor freewheel. You can have another word that grounds both ends of the motor for braking. To run you load a word to start the bridge, and then just XOR that word to run the bridge.
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