我们的PWM口只能通过输出占空比来输出模拟量，但是如果要输出1-60KHz或更高的脉冲频率的话，就不好做到啦。我一直在需找解决方案，无意中找到啦，现提供给大家分享，希望能有所帮助。
源代码如下：
Here are some usage examples of the function:
// Set pin 9's PWM frequency to 3906 Hz (31250/8 = 3906)
// Note that the base frequency for pins 3, 9, 10, and 11 is 31250 Hz
setPwmFrequency(9, 8);
// Set pin 6's PWM frequency to 62500 Hz (62500/1 = 62500)
// Note that the base frequency for pins 5 and 6 is 62500 Hz
setPwmFrequency(6, 1);
// Set pin 10's PWM frequency to 31 Hz (31250/1024 = 31)
setPwmFrequency(10, 1024);
Please keep in mind that changing the PWM frequency changes the Atmega's timers and disrupts the normal operation of many functions that rely on time (delay(), millis(), Servo library).
/**
* Divides a given PWM pin frequency by a divisor.
*
* The resulting frequency is equal to the base frequency divided by
* the given divisor:
* - Base frequencies:
* o The base frequency for pins 3, 9, 10, and 11 is 31250 Hz.
* o The base frequency for pins 5 and 6 is 62500 Hz.
* - Divisors:
* o The divisors available on pins 5, 6, 9 and 10 are: 1, 8, 64,
* 256, and 1024.
* o The divisors available on pins 3 and 11 are: 1, 8, 32, 64,
* 128, 256, and 1024.
*
* PWM frequencies are tied together in pairs of pins. If one in a
* pair is changed, the other is also changed to match:
* - Pins 5 and 6 are paired on timer0
* - Pins 9 and 10 are paired on timer1
* - Pins 3 and 11 are paired on timer2
*
* Note that this function will have side effects on anything else
* that uses timers:
* - Changes on pins 3, 5, 6, or 11 may cause the delay() and
* millis() functions to stop working. Other timing-related
* functions may also be affected.
* - Changes on pins 9 or 10 will cause the Servo library to function
* incorrectly.
*
* Thanks to macegr of the Arduino forums for his documentation of the
* PWM frequency divisors. His post can be viewed at:
* http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1235060559/0#4
*/
void setPwmFrequency(int pin, int divisor) {
byte mode;
if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {
switch(divisor) {
case 1: mode = 0x01; break;
case 8: mode = 0x02; break;
case 64: mode = 0x03; break;
case 256: mode = 0x04; break;
case 1024: mode = 0x05; break;
default: return;
}
if(pin == 5 || pin == 6) {
TCCR0B = TCCR0B & 0b11111000 | mode;
} else {
TCCR1B = TCCR1B & 0b11111000 | mode;
}
} else if(pin == 3 || pin == 11) {
switch(divisor) {
case 1: mode = 0x01; break;
case 8: mode = 0x02; break;
case 32: mode = 0x03; break;
case 64: mode = 0x04; break;
case 128: mode = 0x05; break;
case 256: mode = 0x06; break;
case 1024: mode = 0x7; break;
default: return;
}
TCCR2B = TCCR2B & 0b11111000 | mode;
}
}
提供参考网址：
http://arduino.cc/playground/Code/PwmFrequency
http://arduino.cc/playground/Main/TimerPWMCheatsheet
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发表于 2012-12-29 17:17:55
