Hi Petro, Maybe instead of creating an override you can create a capability like exists for SDIO on NuttX.
It could be used to control features/characteristics unique for some PWM controllers. Buf of course it will need some override/sync flag because some applications will prefer to wait up to the next cycle. BR, Alan On 11/12/22, Petro Karashchenko <petro.karashche...@gmail.com> wrote: > Hello David, > > Thanks for your reply. I fully understand that. In my case I have the half > bridge schema of four pins and PWM frequency is very low. In case I need to > do immediate stop I need to stop pulse generation and short pin to the > ground. It is more because the overall half bridge solution is controlled > by 2 pins with PWM and other 2 pins are controlled as GPIOs. There where > the sync problems come in place. > > Best regards, > Petro > > On Sat, Nov 12, 2022, 9:34 AM David Sidrane <david.sidr...@nscdg.com> > wrote: > >> Hi Petro, >> >> On the STM32 there are shadow registers that buffer the updated data to >> ensure that outputs are updated synchronously with the end of the period. >> There is a bit that can be set to force the update to the shadowed >> registers >> to be immediate, which will change the count of the current period in >> that >> period. This can be dangerous; in that it could extend a pulse and create >> an >> undesired position or speed. In the case of going to 0, this could create >> a >> runt pulse and also create an undesired position or a slow speed (not so >> bad), Because the update is asynchronous the pulse with the output, it is >> not deterministic. So synchronous updates are a good thing most times. >> >> David >> >> >> -----Original Message----- >> From: Petro Karashchenko <petro.karashche...@gmail.com> >> Sent: Friday, November 11, 2022 6:50 PM >> To: dev@nuttx.apache.org >> Subject: PWM fast stop operation >> >> Hello team, >> >> Recently I had a project where I had to control a motor using PWM. In >> general things worked pretty well, but I've met an issue when I need to >> stop >> PWM as soon as possible. My custom board is based on SAMv7 and uses the >> standard NuttX PWM driver. The issue with the SAMv7 PWM peripheral is >> that >> when a PWM stop is issued the PWM generation is not stopped immediately, >> but >> waits at the end of the current cycle. I'm not sure if that is unique to >> SAMv7, so maybe you can give feedback about the other platforms. >> Initially >> I >> tried to replace stop by keeping PWM running and updating config to have >> 0% >> duty cycle, but that still waits till the end of the current cycle to >> apply. >> The SAMv7 PWM has a signal override capabilities, so I used that instead >> of >> stopping the PWM. I've extended the "struct pwm_info_s" structure and >> included an override field there, but feel that it might not be the best >> approach. >> >> I would appreciate your advices on what is the best way to integrate >> output >> override feature into existing PWM driver. >> >> Best regards, >> Petro >> >
