Datasheet

Flyport Wi-Fi and Ethernet Programmer's guide framework 2.3 (rev 1.0) www.openpicus.com

PWMs

Flyport provides up to 9 PWMs using remappable pin function.

QUESTION: What is a PWM signal?

PWM, Pulse Width Modulation, is a digital periodic signal. It is like a square wave, but the duty cycle

is variable. The duty cycle is the ratio between the high level period duration and the low level period

duration, often expressed in %.

A duty cycle of 100% is a signal that is always high, a duty cycle of 0% is always low, and 50% is a

perfect square wave where the high and low durations are the same.

There are 2 main parameters of a PWM signal: the duty cycle discussed above, and the frequency of

the signal, which represents the repetitions per second of our signal.

For example, a PWM with a frequency of 200Hz will have the period:

T = 1/f = 1/200 = 5ms

So every 5ms the period will be repeated. Using a PWM with 25% of duty there will be:

• Total period: 5ms

• High duration: (5ms*25/100) = 1.25 ms

• Low duration: 5ms – 1.25ms = 3.75 ms

QUESTION: How can I use PWM signals?

Normally PWM signal is used to drive a Led or a DC motor. It's possible also to create “virtual” analog

output signal. Note that PWM is not a DAC (digital to analog converter), but a simple way to generate

an analog signal adding some R-C filtering. The R-C filter design is a relatively complex operation that

depends on the frequency of the PWM and on the load at the output pin.