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PwmOut
The PwmOut interface is used to control the frequency and mark-space ratio of a digital pulse train.
Hello World!¶
Example code for dimming an on-board LED
#include "mbed.h"
PwmOut led(LED1);
int main() {
while(1) {
for(float p = 0.0f; p < 1.0f; p += 0.1f) {
led = p;
wait(0.1);
}
}
}
API¶
Details¶
The PwmOut Interface can be used on mbed pins p21-p26, and also on-board LED1-LED4
The PwmOut interface can express the pulse train in many ways depening on how it is to be used. The period and pulse width can be expressed directly in units of seconds, millisecond or microseconds. The pulsewidth can also be expressed as a percentage of the the period.
Implementation details¶
On the mbed LPC2368 and LPC1768, the PwmOut hardware is limited to share the period value between all outputs. Therefore, if you change the period of one output, you change them all. The pulsewidth can be set independently for each output.
Examples¶
Control a R/C model servo
#include "mbed.h"
PwmOut servo(p21);
int main() {
servo.period(0.020); // servo requires a 20ms period
while (1) {
for(float offset=0.0; offset<0.001; offset+=0.0001) {
servo.pulsewidth(0.001 + offset); // servo position determined by a pulsewidth between 1-2ms
wait(0.25);
}
}
}