Hi Justin! I just tried to answer you mail, but the google board doesn't work (once again). I try to answer from my mail client, which I never did before.
Am Sonntag, 2. April 2017 17:26:10 UTC+2 schrieb Justin Pearson: > On the 3.18 kernel, I was able to control the PWM with the PRU without > needing the PRU to initialize the PWM. The trick was to load the PWM capes > "am33xx_pwm" and "bone_pwm_P8_34" before running the PRU code. (And also > loading Derek's cape to initialize the pruss.) Loading the capes causes some > PWM kernel driver to initialize the PWM registers, I assume. Once that's > done, the PRU just has to tweak a couple registers to change the duty cycle. > Is this trick what you're referring to when you say "The kernel driver should > also work"? > > Would this trick of pre-loading the capes also work in a 4.x kernel? > Sorry, I don't know any of the overlays you mentioned. And, as I said, I never used any kernel driver for GPIO, QEP, CAP, PWM or ADC. Instead I use an all-in-one driver (which I named libpruio), that handles all that stuff easier, more flexible and faster than any kernel driver framework. In order to get PWM output, there're just a few registers to set (see file pruio_pwmss.p in the package), so no need for all that multi source overhead. BTW: You're developing PRU code and you're using a real time kernel. May I ask why? Since the PRUSS are very efficient for real time tasks, I see no reason for using additionally a real time kernel. Regards PS: I just checked Derek's cape. From a first glance I found the line compatible = "ti,beaglebone", "ti,beaglebone-black"; is wrong. The order is important, most specific first. It must be compatible = "ti,beaglebone-black", "ti,beaglebone"; And it does more than just enabling the PRUSS (you're loading unnecessary overhead). In the libpruio package there's the tool dts_custom, which you can use to easy create, compile and install minimal custom overlays (single source, no overhead). Am 02.04.2017 um 17:25 schrieb Justin Pearson: > Thank you TJF, I never would have known about that register if you hadn't > mentioned it. One more question (see below): > > On Sat, Apr 1, 2017 at 9:20 PM, TJF <jeli.freih...@gmail.com> wrote: > >> Am Samstag, 1. April 2017 22:18:30 UTC+2 schrieb Justin Pearson: >>> >>> Are you saying that the only way to get PWM in a 4.x kernel is by >>> modifying am33xx-clocks.dtsi? >>> >> >> No. The kernel driver should also work (untested). But in your case >> (controlling the PWM subsystem by PRU code) you have to modify that file. >> (Or you can develop a loadable kernel module that writes to the register.) >> > > On the 3.18 kernel, I was able to control the PWM with the PRU without > needing the PRU to initialize the PWM. The trick was to load the PWM capes > "am33xx_pwm" and "bone_pwm_P8_34" before running the PRU code. (And also > loading Derek's cape > <https://github.com/derekmolloy/exploringBB/blob/master/chp13/overlay/EBB-PRU-Example.dts> > to > initialize the pruss.) Loading the capes causes some PWM kernel driver to > initialize the PWM registers, I assume. Once that's done, the PRU just has > to tweak a couple registers to change the duty cycle. Is this trick what > you're referring to when you say "*The kernel driver should also work*"? > > Would this trick of pre-loading the capes also work in a 4.x kernel? > > Thanks for all your help! > Justin > > > > >> >> >>> Also, how can I verify whether the register is set correctly? >>> >> >> The PRU cannot write to the Control Module registers, but it can read >> them. Get a word from 0x44E10664 and pass it to the ARM code. Bits 0:2 must >> be set to get output from all PWM subsystems. In your case bit 1 set is >> sufficient to get ehrpwm1B working. >> >> Regards >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to a topic in the >> Google Groups "BeagleBoard" group. >> To unsubscribe from this topic, visit https://groups.google.com/d/ >> topic/beagleboard/LZhL4S9taic/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> beagleboard+unsubscr...@googlegroups.com. >> To view this discussion on the web visit https://groups.google.com/d/ >> msgid/beagleboard/3041a94e-58ab-4c28-ad29-ad3a2b90315b%40googlegroups.com >> <https://groups.google.com/d/msgid/beagleboard/3041a94e-58ab-4c28-ad29-ad3a2b90315b%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> >> 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 beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/85f0fe91-f65e-82f8-c6a0-5c8d133db5c4%40gmail.com. For more options, visit https://groups.google.com/d/optout.
