On 2/25/2019 9:17 AM, Damien Dando wrote: > Hi Charles, thanks! > > Note: I tried to post this answer in the public google group but for some > unknown reason google keep deleting my answer right after I post. I also > tried to leave Machinekit group to re-join hoping it would reset something > but no luck.. fuck google! If you happen to known how to solve that let me > know. > > In the end I did recompile the all Machinekit on BBB, took a while but it > eventually worked and I got the dev. env. working now. > > You may also want to look at the timer/capture modules, both in the >> ARM system (with Linux drivers) and there's one module within the PRU >> domain. You can use these to time pulses and you will get several >> orders of magnitude better accuracy (~10 nS) vs. trying to monitor the >> signal with PRU software (~1-10 uS), but that may or may not be >> important depending on the PWM frequency range. > > 10uS is already overkill for my needs ;) > I'm reading feedback signal from ClearPath motors > <https://www.google.com/url?q=https%3A%2F%2Fwww.teknic.com%2Fproducts%2Fclearpath-brushless-dc-servo-motors%2F&sa=D&sntz=1&usg=AFQjCNEvOk7R_8YKWL7kTygoqgTooMdbWA> > and > the PWM frequency is only 50Hz. Also I'm using regular GPIO inputs because > there is too much constraint with dedicated PRU inputs pinout. > Since I saw quite few video with people using those same ClearPath motors > <https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/> on > their CNC, I'm sure many would benefit from having this feature in > Machinekit. > > Also I would be happy to contribute to Machinekit project so I was > wondering what are requirements/process to add a feature/push request to > Machinekit official source code.
Just fork the repo on Github, make your changes, and submit a PR. > In order to integrate it at best into Machinekit source code, that would be > great to have feedback on some question: > @Charles: As it seem you have done a lot of work in the hal_pru_generic > driver, your feedback would be valuable&appreciated :) > > Since I'm not using dedicated PRU inputs, reading a regular GPIO input pin > takes ~170ns (~190ns for GPIO bank 0). For this reason, I aim to read GPIO > bank(s) not more that once per pru period and only if needed. > > I see 2ways of doing that: > > 1. read GPIO inputs "globally" (in similar way as it is done for GPIO > outputs in pru_wait.p > > <https://www.google.com/url?q=https%3A%2F%2Fgithub.com%2Fmachinekit%2Fmachinekit%2Fblob%2Fmaster%2Fsrc%2Fhal%2Fdrivers%2Fhal_pru_generic%2Fpru_wait.p%23L204&sa=D&sntz=1&usg=AFQjCNGBlHA8xVFFCtUPIZQH1MTHfStebA>). > > This requires to add some code in pru_wait.p > > <https://github.com/machinekit/machinekit/blob/master/src/hal/drivers/hal_pru_generic/pru_wait.p> > and/or pru_generic.p > > <https://github.com/machinekit/machinekit/blob/master/src/hal/drivers/hal_pru_generic/pru_generic.p> > and > therefore extends a bit the overall pru period. The major advantage is > that > it would allow any others hal pru "modules" to use any GPIO inputs (the > hal > pru encoder could then be updated to work also with regular GPIO inputs). > 2. read GPIO inputs "locally" in the PWM reader pru task I'm > implementing. The drawback we will need to re-read GPIO input bank in > every > hal pru "module" that use them and therefore wasting PRU period time. > > I see the first solution as the best one. > Looking further, I saw that there is no much unused/free space in PRU > register (r0-32), there are pretty much all used for something. There are quite a few unused registers. See the scratch/reserved registers (used to talk to the hardware multiplier): https://github.com/machinekit/machinekit/blob/master/src/hal/drivers/hal_pru_generic/pru_generic.p#L81-L85 You could also use the per-task registers (R4-11) and a chunk of the scratchpad registers. > However, I > thought about this solution (using GPIOn_Clr and GPIOn_Set): > > - every time a PRU module/task want to read a GPIO pin, it set the > corresponding bit both GPIOn_Clr and GPIOn_Set registers. (I believe pru > module/task using GPIO as output never set both GPIOn_Clr and GPIOn_Set > for > the same pin at the same time since that would be a non sense). > - somewhere around pru_wait.p > > <https://github.com/machinekit/machinekit/blob/master/src/hal/drivers/hal_pru_generic/pru_wait.p#L204> > check > if the result of logical AND (GPIOn_Clr + GPIOn_Set) differs from 0. If > it is then, perform a "long" (~170ns) reading on GPIOn and store the > result > in GPIOn_Set. To avoid conflict with other GPIO outputs, only store > bits/pins where a read was requested. Then the PRU module/task that > requested the reading can read the pin state in GPIOn_Set on the next > pru period. > > or maybe there is some easier solution allocating/using PRU RAM instead of > direct PRU register r0-32 (GPIOn_Clr / GPIOn_Set)... > What are you thought? Do you have any better implementation idea/suggestion? Personally I don't really want to see hal_pru_generic code reading from the fabric, it eats up too much time. I'd rather see "slow" code like this running on the other PRU, leaving the hal_pru_generic code as-is. That said, you're free to do what you want. If I was going to write something like this, I'd probably create a "GPIO read" tasklet that reads the input pins from the gpio bank(s) and stashes the data either in the register bank or in one of the scratchpad banks. Then you can have other tasklets that process GPIO input pin data as needed. ...but really I think you'd be best off just using a PRU direct input pin. IIRC you said you're using a CRAMPS board. If so, several of the SPI signals function as direct PRU inputs and are already tied to a connector via a FET bus level translator so they are bidirectional and 5V tolerant: P9.28 SPI_CS0 P9.29 MISO P9.30 MOSI P9.31 SCK P503 on the CRAMPS board. -- Charles Steinkuehler char...@steinkuehler.net -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to machinekit+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
