Can "allocated pins" on BBB be used as GPIOs ?

[Dhruv Vyas]

Hello,

I recently started working on my BBB A6A. I went through necessary getting started guides and it works like a charm. Now as a part of my project, I need to use some of the GPIOs on P8/P9 header. While googling how to use them as a GPIO, and how to set pinmux and etc, I went through this guide.  http://derekmolloy.ie/gpios-on-the-beaglebone-black-using-device-tree-overlays/ and he explained everything very clearly.

Now my question is : is there any way i can use allocated pins as GPIOs other than available pins ? If yes, how ? If no, why ?

For example, P9_19 and P9_20 are Allocated to (Group: pinmux_i2c2_pins) and hence it can not be used as GPIOs ?

Thanks.

[John Syn]

From: Dhruv Vyas <dhruv....@gmail.com>
Reply-To: <beagl...@googlegroups.com>
Date: Sunday, May 18, 2014 at 2:42 AM
To: <beagl...@googlegroups.com>
Subject: [beagleboard] Can "allocated pins" on BBB be used as GPIOs ?

If pins are also connected to circuitry on the board that cannot be disabled then you cannot use those pins for GPIO. For example, pins used for the eMMC can be used for GPIO as long as eMMC is disabled. Same for LCD pins, but then you cannot use LCD or HDMI. I2C2 isn’t connected to other circuity on the board so you can use it for GPIO. 

Regards,

John

Thanks.

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[Dhruv Vyas]

Thanks John. Got it cleared. :)

[halfbrain]

Would be nice if you could explain how to disable eMMC on debian. I ran out of GPIO's in my project. Tried to use P9_19 and P9_20 (both I2C's) in the device tree overlay but since i did that the overlay doesn't work correctly anymore.

[halfbrain]

how do u use the i2c2 pins? it doesn't work on my bbb if i only change the pinmode to mode 7 in my device tree. have u done additional changes or something like that elsewhere?

[John Syn]

From: halfbrain <adrian....@gmail.com>
Reply-To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Date: Sunday, August 31, 2014 at 2:30 AM
To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Subject: Re: [beagleboard] Can "allocated pins" on BBB be used as GPIOs ?

how do u use the i2c2 pins? it doesn't work on my bbb if i only change the pinmode to mode 7 in my device tree. have u done additional changes or something like that elsewhere?

If you look at /arch/arm/boot/dts/am335x-bone-common.dtsi you will see the i2c2 definition:

&i2c2 {
	status = "okay";
	pinctrl-names = "default";
	pinctrl-0 = <&i2c2_pins>;
	clock-frequency = <100000>;
	cape_eeprom0: cape_eeprom0@54 {
	compatible = "at,24c256";
	reg = <0x54>;
	};
	cape_eeprom1: cape_eeprom1@55 {
	compatible = "at,24c256";
	reg = <0x55>;
	};
	cape_eeprom2: cape_eeprom2@56 {
	compatible = "at,24c256";
	reg = <0x56>;
	};
	cape_eeprom3: cape_eeprom3@57 {
	compatible = "at,24c256";
	reg = <0x57>;
	};
	};

The line “pinctrl-0 = <&i2c2_pins>;” refers to the i2cs_pins label in the pinmux section:

  i2c2_pins: pinmux_i2c2_pins { 

pinctrl-single,pins = < 

0x178 0x73 /* uart1_ctsn.i2c2_sda, SLEWCTRL_SLOW | INPUT_PULLUP | MODE3 */ 

0x17c 0x73 /* uart1_rtsn.i2c2_scl, SLEWCTRL_SLOW | INPUT_PULLUP | MODE3 */ 

 >; 

 };

So, as you can see, i2c2 is used to identify the capes plugged into the BBB. If you don’t need this feature, simply remove or comment out this section and then change the i2c2 pins to gpio pins.

Regards,

John

[halfbrain]

I'm using Derek Molloys device Tree overlays and I'm running debian... I can't find the folder on my bbb .

But I found the "am335x-bone-common.dtsi" in  https://github.com/derekmolloy/boneDeviceTree/tree/master/DTSource3.8.13 which I have on my bbb. I've commented out the section you mentioned but nothing changes. Without using or declaring the I2c2 pins in my Device Tree Overlay I'm able to use all unallocated pins as GPIO Inputs as I declared them in my Device Tree Overlay.

Did i change the wrong am335x-bone-common.dtsi.? Is there another one elsewhere on the debian distribution or do i have to copy the changed file into a specific folder?

[John Syn]

From: halfbrain <adrian....@gmail.com>
Reply-To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>

Date: Monday, September 1, 2014 at 8:23 AM

To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Subject: Re: [beagleboard] Can "allocated pins" on BBB be used as GPIOs ?

I'm using Derek Molloys device Tree overlays and I'm running debian... I can't find the folder on my bbb .

But I found the "am335x-bone-common.dtsi" in  https://github.com/derekmolloy/boneDeviceTree/tree/master/DTSource3.8.13 which I have on my bbb. I've commented out the section you mentioned but nothing changes. Without using or declaring the I2c2 pins in my Device Tree Overlay I'm able to use all unallocated pins as GPIO Inputs as I declared them in my Device Tree Overlay.

Did i change the wrong am335x-bone-common.dtsi.? Is there another one elsewhere on the debian distribution or do i have to copy the changed file into a specific folder?

You need to follow:

http://eewiki.net/display/linuxonarm/BeagleBone+Black#BeagleBoneBlack-LinuxKernel

After the kernel has built, you will see a KERNEL folder which includes the complete Linux Kernel. In that folder, go to /arch/arm/boot/dts and edit the am335x-bone-common.dtsi file. After that, return to the bb-kernel folder and run tools/rebuild.sh script. The build results will be in the deploy folder which you need to copy to your sdcard/“nfs folder”.

Regards,

John

[halfbrain]

Thanks for your quick responses always.
I've tried the Instructions to build the Kernel

git clone https://github.com/RobertCNelson/bb-kernel.git

cd bb-kernel/


git checkout origin/am33x-v3.8 -b tmp




 


but if use the command ./build_kernel.sh . i get this message after the "resolving deltas process". I've tried several times but it always freezes at 96%. Do you have any Idea what went wrong?

this is what i get in the commandshell:

root@beaglebone:/bb-kernel# ./build_kernel.sh
+ Detected build host [Debian GNU/Linux 7.5 (wheezy)]
+ host: [armv7l]
+ git HEAD commit: [e496a19d1fed586a7e82c3cd74f0571491a526ca]
-----------------------------
scripts/gcc: Using: gcc (Debian 4.6.3-14) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-----------------------------
CROSS_COMPILE=
-----------------------------
scripts/git: LINUX_GIT not defined in system.sh
cloning https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git into default location: /bb-kernel/ignore/linux-src
Cloning into '/bb-kernel/ignore/linux-src'...
remote: Counting objects: 3758162, done.
remote: Compressing objects: 100% (567907/567907), done.
remote: Total 3758162 (delta 3168580), reused 3749734 (delta 3160289)
Receiving objects: 100% (3758162/3758162), 794.38 MiB | 1.37 MiB/s, done.
error: index-pack died of signal 968580)
fatal: index-pack failed
root@beaglebone:/bb-kernel#

[John Syn]

From: halfbrain <adrian....@gmail.com>
Reply-To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>

Date: Tuesday, September 2, 2014 at 9:09 AM

To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Subject: Re: [beagleboard] Can "allocated pins" on BBB be used as GPIOs ?

Thanks for your quick responses always.
I've tried the Instructions to build the Kernel

git clone https://github.com/RobertCNelson/bb-kernel.git

cd bb-kernel/


git checkout origin/am33x-v3.8 -b tmp




You need to be building this on your desktop, not on your BBB.

Regards,

John

[Brandon I]

halfbrain,

If you're using angstrom or debian, you can disable the emmc by adding this to the optargs in uEnv.txt on the usb mass storage partition: capemgr.disable_partno=BB-BONE-EMMC-2G

If you're not using hdmi, you can free up those too: capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN,BB-BONE-EMMC-2G

[Brandon I]

halfbrain, I forgot to mention, you should tie the eMMC cmd and clock pins low on P8.20 and P8.21, as suggested by the wiki: http://elinux.org/Beagleboard:BeagleBoneBlack#Onboard_eMMC

[prog...@gmail.com]

Hi John


Sorry for asking you again but it still doesnt work :-(

I've tried several times to build the kernel, also in the Desktop Folder. Yesterday i destroyed my image somehow :-). I reflashed the BBB again with the Debian form my uSD Card and started right with the Kernel building without doing anything else before except the
sudo apt-get update
sudo apt-get install bc lzma lzop libncurses5-dev

which are necessary...

but i get the same error everytime :

root@beaglebone:/home/debian/Desktop/bb-kernel# ./build_kernel.sh

+ Detected build host [Debian GNU/Linux 7.5 (wheezy)]
+ host: [armv7l]
+ git HEAD commit: [e496a19d1fed586a7e82c3cd74f0571491a526ca]

`/home/debian/Desktop/bb-kernel/system.sh.sample' -> `/home/debian/Desktop/bb-kernel/system.sh'

-----------------------------
scripts/gcc: Using: gcc (Debian 4.6.3-14) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-----------------------------
CROSS_COMPILE=
-----------------------------
scripts/git: LINUX_GIT not defined in system.sh

cloning https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git into default location: /home/debian/Desktop/bb-kernel/ignore/linux-src
Cloning into '/home/debian/Desktop/bb-kernel/ignore/linux-src'...
remote: Counting objects: 3758531, done.
remote: Compressing objects: 100% (562572/562572), done.
remote: Total 3758531 (delta 3168898), reused 3755444 (delta 3165993)
Receiving objects: 100% (3758531/3758531), 793.01 MiB | 1.78 MiB/s, done.
error: index-pack died of signal 968898)
fatal: index-pack failed
root@beaglebone:/home/debian/Desktop/bb-kernel#

the whole process also takes very long espacially the resolving deltas process

do you have any idea what I'm doing wrong or whats wrong with my bbb. I'm running my bbb over ssh with putty and without uSD Card.

What am I doing excatly by following your Instructions? I mean i don't have any idea I'm just following your Instructions. Isn't there an easier more newbie-like way? In my Project I need to connect 16 PEC11-Encoders. That means 32 GPIOs. I already got 30 so I just need to more but it seems more complicated than i thought it would be :-)

[prog...@gmail.com]

Hi John

I always get this even after reflashing my whole bbb with Debian.

root@beaglebone:/home/debian/Desktop/bb-kernel# ./build_kernel.sh

+ Detected build host [Debian GNU/Linux 7.5 (wheezy)]
+ host: [armv7l]
+ git HEAD commit: [e496a19d1fed586a7e82c3cd74f0571491a526ca]
-----------------------------
scripts/gcc: Using: gcc (Debian 4.6.3-14) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-----------------------------
CROSS_COMPILE=
-----------------------------
scripts/git: LINUX_GIT not defined in system.sh

cloning https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git into default location: /home/debian/Desktop/bb-kernel/ignore/linux-src
Cloning into '/home/debian/Desktop/bb-kernel/ignore/linux-src'...

remote: Counting objects: 3758531, done.
remote: Compressing objects: 100% (568127/568127), done.
remote: Total 3758531 (delta 3168892), reused 3749886 (delta 3160438)
Receiving objects: 100% (3758531/3758531), 794.38 MiB | 1.43 MiB/s, done.
error: index-pack died of signal 968892)
fatal: index-pack failed
root@beaglebone:/home/debian/Desktop/bb-kernel#


Do you have any Idea what went wrong or what could be wrong with my bbb. I tried the whole process several times and it took a very long everytime espacially the resolving Deltas process. And it always ends up with this Error. What am I doing wrong?

Isn't there an easier way to do that? In my project I got 16 PEC11 Encoders that means I need 32 GPIO's. I already got 15 so i just need 2 more.

[halfbrain]

Hi John

I always get this even after reflashing my whole bbb with Debian.

root@beaglebone:/home/debian/Desktop/bb-kernel# ./build_kernel.sh

+ Detected build host [Debian GNU/Linux 7.5 (wheezy)]
+ host: [armv7l]
+ git HEAD commit: [e496a19d1fed586a7e82c3cd74f0571491a526ca]
-----------------------------
scripts/gcc: Using: gcc (Debian 4.6.3-14) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
-----------------------------
CROSS_COMPILE=
-----------------------------
scripts/git: LINUX_GIT not defined in system.sh

cloning https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git into default location: /home/debian/Desktop/bb-kernel/ignore/linux-src
Cloning into '/home/debian/Desktop/bb-kernel/ignore/linux-src'...
remote: Counting objects: 3758531, done.
remote: Compressing objects: 100% (568127/568127), done.
remote: Total 3758531 (delta 3168892), reused 3749886 (delta 3160438)
Receiving objects: 100% (3758531/3758531), 794.38 MiB | 1.43 MiB/s, done.
error: index-pack died of signal 968892)
fatal: index-pack failed
root@beaglebone:/home/debian/Desktop/bb-kernel#


Do you have any Idea what went wrong or what could be wrong with my bbb. I tried the whole process several times and it took a very long everytime espacially the resolving Deltas process. And it always ends up with this Error. What am I doing wrong?

Isn't there an easier way to do that? In my project I got 16 PEC11 Encoders that means I need 32 GPIO's. I already got 15 so i just need 2 more.

[Robert Nelson]

Probably ran out of space.  Realistically, just use an x86 desktop to run the script.

Regards,

--
Robert Nelson
http://www.rcn-ee.com/

[halfbrain]

Thanks for your Answer Brandon

Just a few questions for my Information:
- If I used the EMMC pins I would need to boot from SD Card everytime?
- And if I used the HMDI Pins it wouldn't be possible to connect the uHdmi Cable to the bbb and connect some screen to it? Because they are connected to the same pins?

The way you unallocated the pins and the way john recommend me to unallocate the pins seem to be very different. To be honest I don't understand the difference of the two ways. Which way is the easier one and can this way be used to unallocate every pin on the bbb? I just wan't to make things trickier than they are :-) But i'm very thankful for your help so far ;-)

[halfbrain]

What ran out of space the bbb? How do I use an x86desktop...btw whats and x86desktop :-)? a 32bit Computer?

I'm sshing with Putty via Network from my Windows 7 64bit Pc. Is that a problem? Doesn't the whole process run on the bbb?

[Robert Nelson]

On Thu, Sep 4, 2014 at 9:36 AM, halfbrain <adrian....@gmail.com> wrote:
> What ran out of space the bbb?

I'll take a good 2-3gb of space in the end. Haven't looked at the
numbers in awhile.

> How do I use an x86desktop...btw whats and
> x86desktop :-)? a 32bit Computer?

"x86" based "linux" desktop.. doesn't matter if it's 32bit/64bit.

[William Hermans]

What is wrong is that you're doing this on your bbb. You should be doing this on a cross compile i386 PC.

What is it you're trying to do ?

[halfbrain]

Ok... if i get that correctly i should ssh into the bbb from a linux pc?

I'd like to do a project that needs 16 PCE-11 Encoders to change different parameter in a Pythonscript. I already got 15 GPIOs with the DeviceTree Overlay i did for the unallocated Pins but I need 2 more Pins. So i somehow would like to use some of the allocated Pins. But it seems more complicated than i thought. And to be honest i don't have any Idea what excatly I'm doing with allocated Pins, I just follow the Instructions here ;-)

[William Hermans]

So you're trying to make a device tree file for the beaglebone black and not recompile a kernel ?

I have no idea why John has you off recompiling the kernel when all you need is a simple cape disable line in uEnv.txt for the eMMC. Depending on what kernel version there are a few different ways to go about this.

[Brandon I]

halfbrain,

> - If I used the EMMC pins I would need to boot from SD Card everytime? 

Correct. You'll use the beaglebone white/sd card images. The beaglebone will automatically boot from the SD card since it wont be able to find the EMMC.

> - And if I used the HMDI Pins it wouldn't be possible to connect the uHdmi Cable to the bbb and connect some screen to it? Because they are connected to the same pins?

No HDMI if you disable HDMI, but you can still ssh/vnc in.

The way I'm suggesting is the proper way to disable built in overlays that are loaded at boot. For some reason, only the hdmi and emmc interfaces are added as overlays that can be disabled at boot. i2c and the likes are hard coded in the dts file. Why? I don't know. Maybe there's a good reason, probably not.

--Brandon

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[halfbrain]

Thank you Brandon and William for your answers and tips. It seems that you both write about the same method... changing some lines of code in the uEnv.txt etc

I will try this one out as soon as possible and will hopefully give you a positive feedback then ;-)

[William Hermans]

From my own blog site:

optargs=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN

This is both for hdmi video and audio. This was prior to later kernel version "images" that now use two different uEnv.txt files. You have a first stage uEnv.txt file and a second stage uEnv.txt file ( for loading secondary environment variables ).

here is an example of the secondary uEnv.txt file which sits in /boot/ on the rootfs.

#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0

uname_r=3.8.13-bone62

#dtb=

cmdline=quiet init=/lib/systemd/systemd

##Example
#cape_disable=capemgr.disable_partno=
#cape_enable=capemgr.enable_partno=

##Disable HDMI/eMMC
#cape_disable=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN,BB-BONE-EMMC-2G

##Disable HDMI
#cape_disable=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN

##Disable eMMC
#cape_disable=capemgr.disable_partno=BB-BONE-EMMC-2G

##Audio Cape (needs HDMI Audio disabled)
#cape_disable=capemgr.disable_partno=BB-BONELT-HDMI
#cape_enable=capemgr.enable_partno=BB-BONE-AUDI-02



##enable BBB: eMMC Flasher:
##make sure, these tools are installed: dosfstools rsync
#cmdline=init=/opt/scripts/tools/eMMC/init-eMMC-flasher-v2.sh

I believe that came out of RCN's August 5th LXDE standalone image.

[John Syn]

From: William Hermans <yyr...@gmail.com>
Reply-To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Date: Thursday, September 4, 2014 at 1:05 PM

To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Subject: Re: [beagleboard] Can "allocated pins" on BBB be used as GPIOs ?

So you're trying to make a device tree file for the beaglebone black and not recompile a kernel ?

I have no idea why John has you off recompiling the kernel when all you need is a simple cape disable line in uEnv.txt for the eMMC. Depending on what kernel version there are a few different ways to go about this.

If you look in /arch/arm/boot/dts/am335x-bone-common.dtsi, i2c2 is used for the cape eeprom. You cannot disable this with uEnv.txt. The OP wanted to use the i2c2 pins for GPIO and the only way you can do this is to rebuild the DT. However, this isn’t explained anywhere for me to reference, but there is a good reference for rebuilding the kernel. 

Regards,

John

[William Hermans]

It is explained in multiple places. You can use dtc to decompile the device tree file on the bbb currently. Open the resultant file in a text editor, and modify it accordingly, then recompile the file with dtc.

This has been explained on these forums at least once( for troubleshooting the sdcard slow 4bit speeds ), and I'm fairly certain ( but not positive ) this technique has been explained on hipstercircuits too.

[John Syn]

From: William Hermans <yyr...@gmail.com>
Reply-To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>

Date: Thursday, September 4, 2014 at 2:22 PM

To: "beagl...@googlegroups.com" <beagl...@googlegroups.com>
Subject: Re: [beagleboard] Can "allocated pins" on BBB be used as GPIOs ?

It is explained in multiple places. You can use dtc to decompile the device tree file on the bbb currently. Open the resultant file in a text editor, and modify it accordingly, then recompile the file with dtc.

This has been explained on these forums at least once( for troubleshooting the sdcard slow 4bit speeds ), and I'm fairly certain ( but not positive ) this technique has been explained on hipstercircuits too.

You are asking a newbie to do what? You can see from his original posting that he was completely lost, so the aim is to keep thing simple. If it isn’t explained on 

http://eewiki.net/display/linuxonarm/BeagleBone+Black

I tend to avoid the solution. 

[halfbrain]

it finally works :-)))

Thanks so much guys for your tips and help, espacially william.

I just added

optargs=capemgr.disable_partno=BB-BONE-EMMC-2G

in the uEnv.txt file to disable all the emmc Pins. now I have more than enough pins for my project.

[chris...@gmail.com]

Thanks A lot! I've been trying to figure out why this was allocated in the mux for sometime.

You wouldn't happen to know where the program that is controlling the user LEDS is located I want to use them for my own purpose, so I want to remove control from whatever program is providing this heartbeat or whatever.

Also, would you know where I can find information on how to load a program at startup of debian?

Sorry for all the questions you just seem to know what your talking about,

regards,

Chris