使Pic Port成为floatig

/*
 * Configure the powersupply to the external serial port.  To do this,
 * we configure a PWM to control the isolated 3V power supply.
 */

TRISC1 = 1;
TRISC2 = 1;

PR2 = 0xFF;
CCP1CON = 0x0c;     /* PWM mode, active high, single output */
CCP2CON = 0x0e;     /* PWM mode, active low, single output */
CCPR1L = 0x80;      /* 50% duty cycle */
CCPR2L = 0x80;      /* 50% duty cycle */
ECCP1AS = 0;        /* auto shutdown off */
ECCP2AS = 0;        /* auto shutdown off */
PIR1bits.TMR2IF = 0;

T2CON = 0x04;       /* Enable T2 timer, prescale and postscale 1:1 */

while (!PIR1bits.TMR2IF)
    ;

TRISC1 = 0;
TRISC2 = 0;