from JP Brown
// servo2.c // // Servo control using push buttons or switches JPB 11/12/00 // ******************************************** // For CC5X C compiler // Xtl frequency 4MHz // A simple r/c servo test program. // This version uses switches to control the servo position. // Port B bit 1 is the servo control signal o/p // Port A bit 0 = 0 resets the servo position to center (pulse = 1.5 ms) // Port A bit 1 moves the servo clockwise when taken low. // Port A bit 2 moves the servo anticlockwise when taken low. // // Note the pulse width range is specified as 1ms to 2ms giving a movement // of 180 deg. but the precise pulse width and mechanical range varies from // manufacturer to manufacturer. // // The pulse width range generated by this program has been found to work // well with a range of servos. // // Connect the servo to a 5volt supply and take the control wire to port A // bit 3, you will need a connection from the PSU 0V to the pic circuit // supply 0V. Connect port A bit 0 to 3 to push buttons (with pullups). // Do not leave the servo running at the extreme range of movement if it // is pushing against the end stop. You can tell when this is happening // by watching the current taken from the PSU which will be high if the // servo is stalled. #include "16F84.H" #define CP_off |= 0x3FFF // copy protect off for 16F84 #pragma config CP_off, PWRTE=on, WDTE=off, FOSC=XT /* assign names to ports and pins */ #pragma bit SERVO @ PORTB.1 #pragma bit RESET_S @ PORTA.0 #pragma bit TURN_C @ PORTA.1 #pragma bit TURN_A @ PORTA.2 /* function prototypes */ void delay_min (void); void delay_var (char n); void pause (void); void main( void) { PORTB = 0b.0000.0000; /* initial value */ TRISB = 0b.0000.0000; /* Port B all o/p */ PORTA = 0b.0.0111; /* initial value */ TRISA = 0b.1110.0111; /* xxx0 0001 */ char position=107; // total time 1.5ms center position while(1) // endless loop { SERVO=1; delay_min(); if (position>0) delay_var(position); SERVO=0; pause(); // 20 ms delay before next pulse if ((TURN_C==0)&&(position<255)) position++; if ((TURN_A==0)&&(position>0)) position--; if (RESET_S==0) position=107; // center the servo } } // end of main void delay_min (void) // 750 uS including overhead { char n=248; do ; while(--n>0); nop(); // padding to produce precise time } // delay = 2 + 2 + (n x 3) -1 +1 +2 = 750us @ 4MHz // 2 for call, 2 for preset n, (n x 3)-1 for loop, 1 padding, 2 for return void delay_var (char n) // adc x 7 uS = 1790us max. { do {nop(); nop(); nop(); nop();} while(--n>0); } // delay= 2 + 2 + (t x 7) -1 +2 us @ 4MHz void pause (void) // delay between pulses approx 20 ms { char n; for (n=0;n<26;n++) { delay_min(); // 750 us } }
Questions:
I try to load your source code to PIC C compiler, but it come out alot error such as undefine port...+
I'm using PIC 16F877A and use to control four servos
Can you help me to solve this problem?
Thank you
file: /Techref/microchip/language/c/io/servo-jpb.htm, 12KB, , updated: 2009/8/26 14:41, local time: 2024/8/31 16:52,
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