# Beaglebone cape support **URL:** \ **Category:** balenaOS\ **Tags:** beaglebone\ **Created:** [December 6, 2018, 12:41pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620 "2018-12-06T12:41:17Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![sei1](https://avatars.discourse-cdn.com/v4/letter/s/f4b2a3/32.png) [@sei1](https://forums.balena.io/u/sei1)\ **Post date:** [December 6, 2018, 12:41pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/1 "2018-12-06T12:41:17Z")
I’m trying to get my Beaglebone (green) to enable ttyS4. I’m running 2.15.1+rev1-dev - the latest download from balenaCloud. If I try to enable it manually by ‘echo BB-UART4-RS485 \> /sys/devices/platform/bone\_capemgr/slots’ I get a kernel oops in \_\_of\_overlay\_create: > [265.832538] bone\_capemgr bone\_capemgr: part\_number ‘BB-UART2-RTSCTS’, version ‘N/A’ > [265.842181] bone\_capemgr bone\_capemgr: slot #4: override > [265.857452] bone\_capemgr bone\_capemgr: Using override eeprom data at slot 4 > [265.887764] bone\_capemgr bone\_capemgr: slot #4: ‘Override Board Name,00A0,Override Manuf,BB-UART2-RTSCTS’ > [265.907736] Unable to handle kernel NULL pointer dereference at virtual address 0000000c > [265.919845] pgd = c7950000 > [265.922680] [0000000c] \*pgd=00000000 > [265.931816] Internal error: Oops: 5 [#1] PREEMPT SMP ARM > [265.937176] Modules linked in: ipt\_REJECT nf\_reject\_ipv4 ipt\_MASQUERADE nf\_nat\_masquerade\_ipv4 br\_netfilter nf\_conntrack\_netlink nfnetlink xfrm\_user xfrm\_algo evdev uio\_pdrv\_genirq uio nls\_ascii nls\_cp437 sch\_fq\_codel > [265.956643] CPU: 0 PID: 1690 Comm: sh Not tainted 4.14.53+ #2 > [265.962418] Hardware name: Generic AM33XX (Flattened Device Tree) > [265.968540] task: dc799e00 task.stack: c79d0000 > [265.973120] PC is at \_\_of\_overlay\_create+0x43c/0xb60 > [265.978113] LR is at \_\_of\_overlay\_create+0x448/0xb60 > [265.983101] pc : [] lr : [] psr: 20070013 > [265.989397] sp : c79d1d58 ip : c79d5298 fp : c79d1dec > … > [266.216921] [] (\_\_of\_overlay\_create) from [] (of\_overlay\_create+0x20/0x24) > [266.225595] [] (of\_overlay\_create) from [] (capemgr\_load\_slot+0x480/0x5d0) > [266.234259] [] (capemgr\_load\_slot) from [] (slots\_store+0x150/0x328) > [266.242403] [] (slots\_store) from [] (dev\_attr\_store+0x28/0x34) > [266.250110] [] (dev\_attr\_store) from [] (sysfs\_kf\_write+0x50/0x54) > [266.258074] [] (sysfs\_kf\_write) from [] (kernfs\_fop\_write+0xf8/0x1d4) > [266.266302] [] (kernfs\_fop\_write) from [] (\_\_vfs\_write+0x28/0x48) > [266.274178] [] (\_\_vfs\_write) from [] (vfs\_write+0xb4/0x1c0) > [266.281528] [] (vfs\_write) from [] (SyS\_write+0x5c/0xbc) > [266.288625] [] (SyS\_write) from [] (\_\_sys\_trace\_return+0x0/0x10) > [266.296415] Code: e584902c e5843034 e584403c e584a028 (e590500c) > [266.478799] —[end trace b1ba7d0f614b6dcb]— Should this work - is this the correct way of enabling it? Thanks. ---
**Author:** ![spanceac](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@spanceac](https://forums.balena.io/u/spanceac)\ **Post date:** [February 21, 2019, 1:33pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/2 "2019-02-21T13:33:16Z")
Hi @sei1, We are preparing a release for Beaglebone devices where you are able to load device tree overlays from u-boot by adding in `uEnv.txt` the following content: ``` enable_uboot_overlays=1 uboot_overlay_addr0=/boot/overlays/BB-UART4-RS485-00A0.dtbo ``` You can download the `2.29.2+rev3` release from staging dashboard and try it. [https://dashboard.balena-staging.io/apps](https://dashboard.balena-staging.io/apps) This release will soon reach production ---
**Author:** ![sei1](https://avatars.discourse-cdn.com/v4/letter/s/f4b2a3/32.png) [@sei1](https://forums.balena.io/u/sei1)\ **Post date:** [March 5, 2019, 1:29pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/5 "2019-03-05T13:29:42Z")
Hi @spanceac, I’ve just got my Beaglebone back and tried it - the 2.29.2+rev3 appears in the main dashboard now too. It looks like it’s working, I can see the UART4 appear in the kernel log when it’s booting. I’ll dig out my RS485 cape and test code 😄 Thanks for your reply. ---
**Author:** ![spanceac](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@spanceac](https://forums.balena.io/u/spanceac)\ **Post date:** [March 5, 2019, 1:58pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/6 "2019-03-05T13:58:24Z")
Hi @sei1, Please let us know how it went. Regards! ---
**Author:** ![sei1](https://avatars.discourse-cdn.com/v4/letter/s/f4b2a3/32.png) [@sei1](https://forums.balena.io/u/sei1)\ **Post date:** [March 6, 2019, 11:14am UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/7 "2019-03-06T11:14:18Z")
Hi @spanceac, Unfortunately it is not working quite yet. Although I can see data on the scope out of UART4-TX, the RTS pin isn’t changing. Looking in /sys/kernel/debug/pinctrl/44e10800.pinmux > group: pinmux\_bb\_uart4\_rs485\_pins > pin 29 (PIN29) > pin 28 (PIN28) > pin 105 (PIN105) I can see that the RX and TX are set to the UART4 peripheral (0x0e & 0x07) == 6 > pin 29 (PIN29) 44e10874 0000000e pinctrl-single > pin 28 (PIN28) 44e10870 0000002e pinctrl-single But the RTS pin is still assigned to GPIO == 7 > pin 105 (PIN105) 44e109a4 00000007 pinctrl-single > **Edit - I don't think this hidden observation was relevant** > > I’ve hidden this bit because I don’t think it is relevant - it looks like the BBG overlay is added after. > > > Looking through the u-boot output, it looks like it detects that I’m using a BBGreen, but loads uboot\_base\_dtb\_univ = am335x-boneblack-uboot.dtb. > > > > debug: [enable\_uboot\_overlays=1] … > > debug: [enable\_uboot\_cape\_universal=] … > > debug: [uboot\_base\_dtb\_univ=am335x-boneblack-uboot.dtb] … > > uboot\_overlays: [uboot\_base\_dtb=am335x-boneblack-uboot.dtb] … > > uboot\_overlays: Switching too: dtb=am335x-boneblack-uboot.dtb … > > loading /boot/am335x-boneblack-uboot.dtb … > > 58048 bytes read in 41 ms (1.3 MiB/s) > > uboot\_overlays: [fdt\_buffer=0x60000] … > > uboot\_overlays: loading /boot/overlays/M-BB-BBG-00A0.dtbo … > > 277 bytes read in 148 ms (1000 Bytes/s) > > uboot\_overlays: loading /boot/overlays/BB-UART4-RS485-00A0.dtbo … > > 1127 bytes read in 173 ms (5.9 KiB/s) > > uboot\_overlays: loading /boot/overlays/BB-BONE-eMMC1-01-00A0.dtbo … > > 1105 bytes read in 91 ms (11.7 KiB/s) > > uboot\_overlays: loading /boot/overlays/BB-ADC-00A0.dtbo … > > 695 bytes read in 85 ms (7.8 KiB/s) > > uboot\_overlays: add [enable\_uboot\_cape\_universal=1] to /boot/uEnv.txt to enable… Any thoughts? Thanks. ---
**Author:** ![spanceac](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@spanceac](https://forums.balena.io/u/spanceac)\ **Post date:** [March 7, 2019, 10:59am UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/8 "2019-03-07T10:59:06Z")
Hi @sei1, According to the dts, the RTS gpio is `rts-gpio = <&gpio3 19 1>;` [https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-UART4-RS485-00A0.dts](https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BB-UART4-RS485-00A0.dts) That would mean RTS gpio is GPIO3\_19 or as Linux sees it: 3\*32+19 = gpio115 Regards! ---
**Author:** ![sei1](https://avatars.discourse-cdn.com/v4/letter/s/f4b2a3/32.png) [@sei1](https://forums.balena.io/u/sei1)\ **Post date:** [March 7, 2019, 3:45pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/9 "2019-03-07T15:45:05Z")
Thanks for that reference @spanceac. Sorry, it’s been a while since I looked in the dts and I guess I was just assuming it would be the UART4\_RTS pin. So I suppose my now problem is that rts-gpio is only used in the omap-serial driver > $ grep -Rl rts-gpio linux > linux/drivers/tty/serial/imx.c > linux/drivers/tty/serial/omap-serial.c > linux/drivers/tty/serial/sirfsoc\_uart.c but the kernel config uses the 8250 driver > $ gunzip -c config.gz | grep “SERIAL\_.\*OMAP” > CONFIG\_SERIAL\_8250\_OMAP=y > CONFIG\_SERIAL\_8250\_OMAP\_TTYO\_FIXUP=y > #CONFIG\_SERIAL\_OMAP is not set I’ll take a look into rolling my own dtbo to enable the RTS pin instead of that no-longer supported gpio! Thanks very much for your help 👍 ---
**Author:** ![sei1](https://avatars.discourse-cdn.com/v4/letter/s/f4b2a3/32.png) [@sei1](https://forums.balena.io/u/sei1)\ **Post date:** [March 7, 2019, 4:42pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/10 "2019-03-07T16:42:40Z")
Good news is I tried the UART2\_RTSCTS overlay and I’m getting the expected output in my scope! Cheers 🙂 ---
**Author:** ![imrehg](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/imrehg/32/36_2.png) [@imrehg](https://forums.balena.io/u/imrehg)\ **Post date:** [March 7, 2019, 6:34pm UTC](https://forums.balena.io/t/beaglebone-cape-support/4620/11 "2019-03-07T18:34:02Z")
Glad to hear, cheers for the feedback, @sei1!