Thanks for the update dieter! I didn't know kernel version 4.1 was recently released... well, I now know what I'm going to be doing over the next month with our team's Repository.
On Fri, Aug 14, 2015 at 1:30 PM, <[email protected]> wrote: > I see someone has recently asked a question on this old post. > > Controlling pwm using linux is nicely documented in kernel docs: > https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-pwm > > controlling simple servo takes period 20 ms and duty_cycle 1 - 2 ms, start > with these values > echo 20000000 > /sys/class/pwm/pwmchip[num]/pwm[num]/period > ... rest is up to you > > As for the 'howto' described by Tekuconcept in previous reply, I wouldn't > bother about modifying dtb files anymore: > -Upgrade kernel to 4.1 (since this post is originally about the 3.14 > kernel) > --- add 'deb [arch=armhf] http://repos.rcn-ee.com/ubuntu trusty > main' to apt sources (modify to own needs), install new linux-image. > --- modify /boot/uEnv.txt or /boot/uboot/uEnv.txt so the new kernel > is loaded, I mixed up my original uEnv and the suggestions from: > > https://eewiki.net/display/linuxonarm/BeagleBone+Black#BeagleBoneBlack-DealingwitholdBootloaderineMMC > --- dont screw up uEnv... (manual loading of kernel image in memory > using uboot console is possible with serial debugger but painfull...) > -clone 'bb-overlays' github repo and install > -clone 'universal-io' github repo and install > -reboot (took me an hour to figure this one out...) > Now you can 'config-pin overlay cape-universaln', 'config-pin P[num] pwm'. > (all in user space) > > That's about it, works flawless. (took me a couple of days to figure > everything out though, as hobbyist it's fishing for the correct info on the > web...) > > kind regards, > Dieter > > > > > > > > > > On Wednesday, July 15, 2015 at 1:46:00 PM UTC+2, [email protected] wrote: >> >> after doing so how do you control duty cycle, period...? >> >> On Thursday, April 16, 2015 at 7:29:59 AM UTC-6, TekuConcept wrote: >>> >>> >>> - config-pin [pin] [state] will mux the pins to the PWM Subsystems >>> - Modifying am33xx.dtsi under the dtb-rebuilder project such that: >>> epwmss0, epwmss1, and epwmss2 status = "okay", and their children, >>> ehrpwm0, >>> ehrpwm1, and erhpwm2 status = "okay", will enable the system clocks for >>> each subsystem. This equivalent to setting the following registers to the >>> given values in their respective order: >>> >>> reg[0x44E00000] = 0x0 *# CM_PER_L4L3_CLKSTCTRL.CLKTRCTRL = NO_SLEEP* >>> reg[0x44E000D4] = 0x2* # CM_PER_EPWMSS0_CLKCTRL.MODULEMODE = ENABLE* >>> reg[0x44E000CC] = 0x2 *# CM_PER_EPWMSS1_CLKCTRL.MODULEMODE = ENABLE* >>> reg[0x44E000D8] = 0x2* # CM_PER_EPWMSS2_CLKCTRL.MODULEMODE = ENABLE* >>> >>> - However, after all this, the PWM subsystems will still not work >>> because the Time Based Clocks are not enabled. To enable them, one would >>> need kernel elevated privileges: such as modifying the register through a >>> simple kernel module. >>> >>> reg[0x44E10664] = 0x7 # CONTROL_MODULE.pwmss_ctrl = pwmss0_tbclken | >>> (pwmss1_tbclken << 1) | (pwmss2_tbclken << 2) >>> >>> Using a simple kernel module I built for hardware debugging, I was able >>> to confirmed this. (Look at ioremap & iounmap under kernel module >>> development) >>> >> -- > 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/KMIXJPa4IQI/unsubscribe. > To unsubscribe from this group and all its topics, 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.
