自学教程：C++ wait_us函数代码示例

/************ Solid PWM ************/void sol_pwm(DigitalOut pwm, int r_turn, int l_turn){    for(i=0; i<10; i++)    {        pwm = 1;        wait_us(r_turn);        pwm = 0;        wait_ms(26);    }    for(i=0; i<10; i++)    {        pwm = 1;        wait_us(1525);        pwm = 0;        wait_ms(26);    }    for(i=0; i<10; i++)    {        pwm = 1;        wait_us(l_turn);        pwm = 0;        wait_ms(26);    }    for(i=0; i<10; i++)    {        pwm = 1;        wait_us(1525);        pwm = 0;        wait_ms(26);    }}

/************ Liquid PWM ************/void liq_pwm(DigitalOut pwm, int drop){    for(i=1000; i<drop; i=i+25)    {        pwm = 1;        wait_us(i);        pwm = 0;        wait_ms(26);    }    wait(3);    for(i=0; i<40; i++)    {        pwm= 1;        wait_us(1300);        pwm = 0;        wait_ms(26);    }    wait(3);    for(i=1300; i>1000; i=i-25)    {        pwm= 1;        wait_us(i);        pwm = 0;        wait_ms(26);    }    wait(7);}

void reset_rn42(){	P3OUT &= ~BIT0;	wait_us(BLUETOOTH_RESET_HOLD_TIME);	P3OUT |= BIT0;	wait_us(BLUETOOTH_STARTUP_TIME);}

void VNH5019::clear_fault(){        // if ENDIAG is high, then there is no fault        if (ENDIAG.read())        return;        // toggle the inputs        INA = 0;        INB = 0;        wait_us(250);        INA = 1;        INB = 1;        wait_us(250);        // pull low all inputs and wait 1600us for t_DEL        INA = 0;        INB = 0;        PWM = 0;        ENDIAG.output();        ENDIAG = 0;        wait_us(1600);        // and finally re-enable the motor        ENDIAG.input();}

// Based on http://arduinodev.woofex.net/2012/12/01/standalone-sharp-dust-sensor/float GP2Y10::read(){	float voMeasured = 0;	float calcVoltage = 0;	float dustDensity = 0;	led = 0;	wait_us(SAMPLING_TIME);	voMeasured = analog; // read the dust value	wait_us(DELTA_TIME);	led = 1; // turn the LED off	wait_us(SLEEP_TIME);	// 0 - 3.3V mapped to 0 - 1023 integer values	// recover voltage	calcVoltage = voMeasured * 3.3;	// linear eqaution taken from http://www.howmuchsnow.com/arduino/airquality/	// Chris Nafis (c) 2012	dustDensity = 0.17 * calcVoltage - 0.1;	return dustDensity;}

uint8_t matrix_scan(void){    if (mcp23018_status) { // if there was an error        if (++mcp23018_reset_loop == 0) {            // since mcp23018_reset_loop is 8 bit - we'll try to reset once in 255 matrix scans            // this will be approx bit more frequent than once per second            print("trying to reset mcp23018/n");            mcp23018_status = init_mcp23018();            if (mcp23018_status) {                print("left side not responding/n");            } else {                print("left side attached/n");                frenchdev_blink_all_leds();            }        }    }#ifdef DEBUG_MATRIX_SCAN_RATE    matrix_scan_count++;    uint32_t timer_now = timer_read32();    if (TIMER_DIFF_32(timer_now, matrix_timer)>1000) {        print("matrix scan frequency: ");        pdec(matrix_scan_count);        print("/n");        matrix_timer = timer_now;        matrix_scan_count = 0;    }#endif    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {        select_row(i);        wait_us(30);  // without this wait read unstable value.        matrix_row_t cols = read_cols(i);        if (matrix_debouncing[i] != cols) {            matrix_debouncing[i] = cols;            if (debouncing) {                debug("bounce!: "); debug_hex(debouncing); debug("/n");            }            debouncing = DEBOUNCE;        }        unselect_rows();    }    if (debouncing) {        if (--debouncing) {            wait_us(1);            // this should be wait_ms(1) but has been left as-is at EZ's request        } else {            for (uint8_t i = 0; i < MATRIX_ROWS; i++) {                matrix[i] = matrix_debouncing[i];            }        }    }    matrix_scan_quantum();    return 1;}

int main(){    float duration = 0.0;    float distance = 0.0;    status = false;        while(1)     {                triggerpin = 0;        wait_us(1); 					// Wait for 1us for clean low pulse        triggerpin = 1;        wait_us(10);					// Trigger Pulse of 10us        triggerpin = 0;                                   while(!echopin);				//Poll echo pin for High        timer.start();     				//start Timer                   while(echopin);   				//Poll echo pin for low        timer.stop();    				//Stop timer                duration = (float)(timer.read_us());			//Read Timer Value = Echo High Time        //terminal.printf("/n Timer Reading cm : %f /n", duration);                distance = cal_distance(duration);				        terminal.printf("/n Object Distance cm : %f /n", distance);                timer.reset();					//Reset Timer                    wait(1);						// Repeat Trigger after 1sec    }}

int	usbSendBytes(uchar *data,int size){	if(size==0) wait_us(140);			// 0byte packet
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