Hi all,
Perhaps someone understands the device tree overlay file format better than
I do (I sure hope so). Again, my purpose here is to be able to use a 1-wire
interface on the Beaglebone Blue using one of the 6 GPIO pins connected to
a header. I have selected GPIO1_25 which seems to be otherwise
unencumbered, and I believe that maps to PIN57.
I'm currently trying to understand the following sections of the dts file
format:
/* state the resources this cape uses */
exclusive-use =
/* the pin header uses */
"P9.12";
/*
* Free up the pins used by the cape from the pinmux helpers.
*/
fragment@0 {
target = <&ocp>;
__overlay__ {
P9_12_pinmux { status = "disabled"; };
};
};
First, the exclusive-use list can include multiple features. According to
the Adafruit BBB Device Tree manual, this can include both pins and
hardware features (like a uart). I don't see where it ties pin headers to
anything else, so it seems I can use something arbitrary here and it won't
immediately break anything (though it will eventually cause me problems if
that same device is used elsewhere but has a different correct name). I
intend to use the following line: exclusive-use = "P1.25";
Second, the fragment@0 pinmux statement P9_12_pinmux... where does that
thing come from? I would like to use something along the lines of
P1_25_pinmux if it existed, but in all of bb.org-overlays there is no use
of P1_25, because on the non-blue boards that pin doesn't come out
anywhere. So where is this defined so that I can create a new one, or just
write it in manually with the correct format?
Ultimately all I really want is to get the 1-wire driver to talk to a
different pin but I also want to understand what is going on here. My final
target will be both a Pocketbeagle and a Green/Black board and I need to be
able to reconfigure UARTs and I2C ports to do that, so I'd like to know
what I am up to when I change these files.
Thanks in advance for any words of advice.
Best,
Jim
On Fri, Nov 30, 2018 at 5:33 PM <[email protected]> wrote:
> Hi,
>
> I have several questions and hope someone can help. I'm trying to figure
> out how to configure ports on a beaglebone, generically. I haven't found a
> good site which describes any of this thanks to the relatively recent
> changes in how device tree overlays are handled. I'd like to be able to
> configure ports differently from how they ship, so I'm looking to develop
> generic understanding as well as to figure out my specific problem on how
> to configure a port differently:
>
> I'm trying to configure 1-wire on a Beaglebone Blue using the latest iot
> build on beaglebone.org. The BB Blue has 6 free GPIOs which are pinned to
> connectors. Of the 6, looking at the dtb-rebuilder repo it seems that
> GPIO1_25 has the fewest number of hits there so perhaps this one is least
> likely to be used elsewhere. I've modified a dts file from bb-overlays.org
> repository, and guessed my way to the correct offset value for what I think
> should be PIN57 and produced and compiled the following dts:
>
> /dts-v1/;
> /plugin/;
>
> / {
> compatible = "ti,beaglebone", "ti,beaglebone-black",
> "ti,beaglebone-green";
>
> /* identification */
> part-number = "BB-W1-P1.25";
> version = "00A0";
>
> /* state the resources this cape uses */
> exclusive-use =
> /* the pin header uses */
> "P1.25";
>
> /*
> * Free up the pins used by the cape from the pinmux helpers.
> */
> fragment@0 {
> target = <&ocp>;
> __overlay__ {
> P1_25_pinmux { status = "disabled"; };
> };
> };
>
> fragment@1 {
> target = <&am33xx_pinmux>;
> __overlay__ {
>
> dallas_w1_pins: pinmux_dallas_w1_pins {
> pinctrl-single,pins = <
> 0x0e4 0x37
> >;
> };
> };
> };
>
> fragment@2 {
> target-path="/";
> __overlay__ {
>
> onewire {
> status = "okay";
> pinctrl-names = "default";
> pinctrl-0 = <&dallas_w1_pins>;
>
> compatible = "w1-gpio";
> gpios = <&gpio1 25 0>;
> };
> };
> };
> };
>
>
> In compiling this I get the following warnings, which don't mean much to
> me yet:
> dtc -O dtb -o BB-W1-P1.25-00A0.dtb BB-W1-P1.25-00A0.dts -@
> BB-W1-P1.25-00A0.dtb: Warning (unit_address_vs_reg): Node /fragment@0 has
> a unit name, but no reg property
> BB-W1-P1.25-00A0.dtb: Warning (unit_address_vs_reg): Node /fragment@1 has
> a unit name, but no reg property
> BB-W1-P1.25-00A0.dtb: Warning (unit_address_vs_reg): Node /fragment@2 has
> a unit name, but no reg property
>
> In my /boot/uEnv.txt I have made the following changes, on the suspicion
> that there may be some sharing of the pin with video features:
> uboot_overlay_addr0=/home/debian/BB-W1-P1.25-00A0.dtb
> disable_uboot_overlay_video=1
>
> Finally:
> root@beaglebone:/opt/scripts/tools# ./version.sh
> git:/opt/scripts/:[1aa73453b2c980b75e31e83dab7dd8b6696f10c7]
> eeprom:[A335BNLTBLA21722EL002623]
> model:[TI_AM335x_BeagleBone_Blue]
> dogtag:[BeagleBoard.org Debian Image 2018-10-07]
> bootloader:[microSD-(push-button)]:[/dev/mmcblk0]:[U-Boot
> 2018.09-00002-g0b54a51eee]:[location: dd MBR]
> bootloader:[eMMC-(default)]:[/dev/mmcblk1]:[U-Boot
> 2017.05-rc1-00002-g35aecb]:[location: dd MBR]
> kernel:[4.14.71-ti-r80]
> nodejs:[v6.15.0]
>
> device-tree-override:[uboot_overlay_addr0=/home/debian/BB-W1-P1.25-00A0.dtb]
> uboot_overlay_options:[enable_uboot_overlays=1]
>
> uboot_overlay_options:[uboot_overlay_addr0=/home/debian/BB-W1-P1.25-00A0.dtb]
> uboot_overlay_options:[disable_uboot_overlay_video=1]
>
> uboot_overlay_options:[uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-14-TI-00A0.dtbo]
> uboot_overlay_options:[enable_uboot_cape_universal=1]
> pkg check: to individually upgrade run: [sudo apt install --only-upgrade
> <pkg>]
> pkg:[bb-cape-overlays]:[4.4.20181120.0-0rcnee0~stretch+20181120]
> pkg:[bb-wl18xx-firmware]:[1.20180517-0rcnee0~stretch+20180517]
> pkg:[kmod]:[23-2rcnee1~stretch+20171005]
> pkg:[librobotcontrol]:[1.0.4-git20181123.0-0rcnee0~stretch+20181124]
> pkg:[firmware-ti-connectivity]:[20170823-1rcnee1~stretch+20180328]
> groups:[debian : debian adm kmem dialout cdrom floppy audio dip video
> plugdev users systemd-journal i2c bluetooth netdev cloud9ide gpio pwm eqep
> admin spi tisdk weston-launch xenomai]
> cmdline:[console=ttyO0,115200n8 bone_capemgr.uboot_capemgr_enabled=1
> root=/dev/mmcblk0p1 ro rootfstype=ext4 rootwait coherent_pool=1M
> net.ifnames=0 quiet]
> dmesg | grep pinctrl-single
> [ 1.089162] pinctrl-single 44e10800.pinmux: 142 pins at pa f9e10800
> size 568
> [ 30.947099] pinctrl-single 44e10800.pinmux: pin PIN57 already requested
> by ocp:helper; cannot claim for onewire
> [ 31.202623] pinctrl-single 44e10800.pinmux: pin-57 (onewire) status -22
> [ 31.454403] pinctrl-single 44e10800.pinmux: could not request pin 57
> (PIN57) from group pinmux_dallas_w1_pins on device pinctrl-single
> dmesg | grep gpio-of-helper
>
>
> I'm still new with the Beaglebone/linux configuration, sorry if any of
> these things demonstrate my stupidity. Thanks in advance for any help.
>
> Best,
>
> Jim
>
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