the PWM pulse rate should not be effected by any software - Period. Changing rates now perhaps would be. sysfs for instance would be slower than using mmap(), or the PRU's, but I'm not exactly sure that the speed of which you can change the pulse rate is all that important. For most use cases . . . As something like the control for DC/DC switching would need to change dynamically, and very quickly.
Anyway, given this, the maximum frequency of the PWM should be what is listed in the TRM for the hardware module. On Fri, Feb 26, 2016 at 7:05 AM, Dennis Lee Bieber <[email protected]> wrote: > On Fri, 26 Feb 2016 03:33:54 -0800 (PST), > [email protected] declaimed the following: > > >could anyone tell me what the maximum frequency of PWM is? Assuming you > use > >Adafruit_BBIO library? Could I produce 52Mhz clear square wave? > > My time with Google wasn't the most forthcoming. I saw references > to > the PWM module using either 100 or 200MHz clock, and if it is capable of > toggling the output on each tick that would result in a 50 (or 100) MHz > signal. Whether that would be a square wave would depend on the slew rate > of the output drivers, overshoot and ringing on the circuits, etc. > > At 52MHz you are practically in the US 6m amateur radio band -- I > wouldn't think any processor could reliably modulate a signal at that rate. > Most uses of PWM are to produce a form of analog output using capacitors to > level out the switching with the ratio of on/off controlling the output > voltage. Capacitors add to the response time (too small a capacitor and you > still get a square wave output as it saturates too fast; too large and you > may never get to the extreme values as the input switches faster than the > capacitor can charge). > > > -- > Wulfraed Dennis Lee Bieber AF6VN > [email protected] HTTP://wlfraed.home.netcom.com/ > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
