The only overlay I know for a fact that works with recent kernels is
universaln. Which is one of the universal io overlays. But here is one I
personally made that works for all ehrpwms . . . keep in mind the file name
has to be univ-wph-00A0.dts . . . But this file is what universaln has it
in for pwm exactly. I just stripped out the pwm stuff and put it into this
file.
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black",
"ti,beaglebone-green";
/* identification */
part-number = "univ-wph";
version = "00A0";
/* state the resources this cape uses */
exclusive-use =
/* the pin header uses */
"P8.13", /* EHRPWM2B - ZONE 6 PWM */
"P8.19", /* EHRPWM2A - ZONE 4 PWM */
"P9.14", /* EHRPWM1A - ZONE 3 PWM */
"P9.16", /* EHRPWM1B - ZONE 5 PWM */
"P9.21", /* EHRPWM0A - ZONE 2 PWM */
"P9.22", /* EHRPWM0B - ZONE 1 PWM */
/* the hardware ip uses */
"ehrpwm0A",
"ehrpwm0B",
"ehrpwm1A",
"ehrpwm1B",
"ehrpwm2A",
"ehrpwm2B";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
/* P8_13 (ZCZ ball T10) */
P8_13_pwm_pin: pinmux_P8_13_pwm_pin {
pinctrl-single,pins = <0x024 0x24>; }; /* Mode 4,
Pull-Down, RxActive */
/* P8_19 (ZCZ ball U10) */
P8_19_pwm_pin: pinmux_P8_19_pwm_pin {
pinctrl-single,pins = <0x020 0x24>; }; /* Mode 4,
Pull-Down, RxActive */
/* P9_14 (ZCZ ball U14) */
P9_14_pwm_pin: pinmux_P9_14_pwm_pin {
pinctrl-single,pins = <0x048 0x26>; }; /* Mode 6,
Pull-Down, RxActive */
/* P9_16 (ZCZ ball T14) */
P9_16_pwm_pin: pinmux_P9_16_pwm_pin {
pinctrl-single,pins = <0x04c 0x26>; }; /* Mode 6,
Pull-Down, RxActive */
/* P9_21 (ZCZ ball B17) */
P9_21_pwm_pin: pinmux_P9_21_pwm_pin {
pinctrl-single,pins = <0x154 0x33>; }; /* Mode 3,
Pull-Up, RxActive */
/* P9_22 (ZCZ ball A17) */
P9_22_pwm_pin: pinmux_P9_22_pwm_pin {
pinctrl-single,pins = <0x150 0x33>; }; /* Mode 3,
Pull-Up, RxActive */
};
};
fragment@1 {
target = <&ocp>;
__overlay__ {
P8_13_pinmux {
compatible = "bone-pinmux-helper";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&P8_13_pwm_pin>;
};
P8_19_pinmux {
compatible = "bone-pinmux-helper";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&P8_19_pwm_pin>;
};
P9_14_pinmux {
compatible = "bone-pinmux-helper";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&P9_14_pwm_pin>;
};
P9_16_pinmux {
compatible = "bone-pinmux-helper";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&P9_16_pwm_pin>;
};
P9_21_pinmux {
compatible = "bone-pinmux-helper";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&P9_21_pwm_pin>;
};
P9_22_pinmux {
compatible = "bone-pinmux-helper";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&P9_22_pwm_pin>;
};
};
};
fragment@20 {
target = <&epwmss0>;
__overlay__ {
status = "okay";
};
};
fragment@21 {
target = <&ehrpwm0>;
__overlay__ {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <>;
};
};
fragment@23 {
target = <&epwmss1>;
__overlay__ {
status = "okay";
};
};
fragment@24 {
target = <&ehrpwm1>;
__overlay__ {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <>;
};
};
fragment@25 {
target = <&epwmss2>;
__overlay__ {
status = "okay";
};
};
fragment@26 {
target = <&ehrpwm2>;
__overlay__ {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <>;
};
};
};
On Wed, Jul 27, 2016 at 4:40 AM, <[email protected]> wrote:
> Hello,
>
> thanks very much for your quick reply.
>
> - *Concerning the Kernel:* If I enter the command uname -a I get the
> following output: Linux beaglebone 4.4.9-ti-r25 #1 SMP Thu May 5 23:08:13
> UTC 2016 armv7l GNU/Linux. Therefore I assume I am using Kernel 4.4.9
> - *Concerning the Code:* Well there is no code yet. I assumed that
> the PWM could be controlled over files, therefore just as I control GPIOS
> by writing the desired outputs in the appropriate files. I tried to control
> the PWM by writing the desired duty_cycle in the file. So I hoped that I
> could access the PWM from my c++ code by simple file access. However as I
> mentioned, writing the setting duty_cycle=5000, period=10000 and
> enable=1 in the files I described in my original post, I could not
> produce any outputs.
>
> - I also tried to use a custom device tree overlay. I generated it
> using this Website:
>
> http://kilobaser.com/blog/2014-07-28-beaglebone-black-devicetreeoverlay-generator#dtogenerator
>
> with the parameters: P8_36, fastslew, output, pulldown, mode2.
> This gave me the overlay code:
>
> /*
> * Copyright (C) 2013 CircuitCo
> À * This program is free software; you can redistribute it and/or
> modify
> * it under the terms of the GNU General Public License version 2 as
> * published by the Free Software Foundation.
> *
> * This is a template-generated file from BoneScript
> */
> /dts-v1/;
> /plugin/;
>
> / {
> compatible = "ti,beaglebone", "ti,beaglebone-black";
>
> /* identification */
> part-number = "BS_PWM_P8_36_0x2";
>
> /* state the resources this cape uses */
> exclusive-use =
> /* the pin header uses */
> "P8.36",
> /* the hardware IP uses */
> "ehrpwm1A";
>
> fragment@0 {
> target = <&am33xx_pinmux>;
> __overlay__ {
> bs_pwm_P8_36_0x2: pinmux_bs_pwm_P8_36_0x2 {
> pinctrl-single,pins = <0x0c8 0x2>;
> };
> };
> };
>
> fragment@1 {
> target = <&ocp>;
> __overlay__ {
> bs_pwm_test_P8_36 {
> compatible = "pwm_test";
> pwms = <&ehrpwm1 0 500000 0>;
> pwm-names = "PWM_P8_36";
>
> pinctrl-names = "default";
> pinctrl-0 = <&bs_pwm_P8_36_0x2>;
>
> enabled = <1>;
> duty = <0>;
> status = "okay";
> };
> };
> };
> };
>
> which I copied in /lib/firmware/bspwm_P8_36_2-00A0.dts
> and compiled with dtc -O dtb -o /lib/firmware/bspwm_P8_36_2-00A0.dtbo
> -b 0 -@ /lib/firmware/bspwm_P8_36_2-00A0.dts
> After that I loaded the am33xx_pwm as well as the compiled overlay but
> again I was unable to produce any output by writing the already mentioned
> values into the files.
> Loading the overlay also generated read only files which I was unable
> to write any values into, even after running chmod a+w and writing as root.
>
>
> Therefore the Question remains: How can I use the PWM Outputs of the
> Beaglebone black with C++ code?
>
> Thanks again for your help and best regards,
> Phil
> T
>
> --
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