Re: PWM fast stop operation
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 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 > 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 >> 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 >> >
Re: PWM fast stop operation
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 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 > 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 >
RE: PWM fast stop operation
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 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
