GPIO on dm816x-evm

B M

As a newbie, can I ask for further information on gpio and possible sysfs. I have read Documentation/gpio.txt Documentation/sysfs-rules.txt to try to understand this better but I am still in the dark. I would like to be use the command line to modify some gpio lines (along the lines of "Paths in Sysfs" in Documentation/gpio.txt). I am using the DM816x Spectrum Development Kit (816x/389x EVM and I/O daughter card). There is a lot of information across multiple documents and wikis. I hope that someone with experience in this area can provide a quick route to gpio testing.

I would like to understand better the relationship between the MUX setup, GPIO number and relationship with gp0 and gp1 and what they map to on the EVM board. Any hints or links to GPIO on the DM816X would be appreciated.

Thanks!

over 14 years ago

0 MarcPyne over 14 years ago

TI__Mastermind 25055 points

Hello,

From a hardware perspective, please refer to the GPIO Terminal Functions table and the PINCTRLx Registers table in the datasheet for pinmux info. The pinmux utility available in the product folder can also be very helpful. The EVM information is available at:

http://support.spectrumdigital.com/boards/evm816x/reve/

Regards,
Marc

0 B M over 14 years ago in reply to MarcPyne

Prodigy 210 points

Thanks Marc, I have been working through these documents.

For my testing purposes, I have chosen the GPIO on JP2 (just because it is accessible on the daughter card for probing), in particular GP0[24].

So I set TI816X_MUX(SC1_C4, OMAP_MUX_MODE1) in linux-2.6.37-psp04.00.00.10/arch/arm/mach-omap2/board-ti8168evm.c.

Now I use sysfs to access this pin

root@dm816x-evm:/sys/class/gpio# echo 24 > export
root@dm816x-evm:/sys/class/gpio# cd gpio24
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo "high" > direction
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo 1 > value

I do not see any change on the pin level. What is the flaw in the above steps. Should I target another, more appropriate GPIO pin on the EVM board?

Thanks!

0 Anil over 14 years ago in reply to MarcPyne

TI__Expert 6655 points

Hi LiamD,

1. Follow these steps for controlling the GPIO lines from sysfs entries.

a. Export, which GPIO pin you want to control. Below steps are done with respect to GPIO30 (an example).

$ echo 30 > /sys/class/gpio/export

b. Change the GPIO pin direction to in/out

$ echo "out" > /sys/class/gpio/gpio30/direction

$ echo "in" > /sys/class/gpio/gpio30/direction

c. Changing the value

$ echo 1 > /sys/class/gpio/gpio30/value

$ echo 0 > /sys/class/gpio/gpio30/value

d. Unexport the GPIO pin

$ echo 30 > /sys/class/gpio/unexport

Sysfs entries are created from 0 - 63 in case of DM816X because it has two GPIO banks 0 and 1.

Note: GPIO's which are used already in the drivers can not be control from sysfs, unless untill driver export that particular pin.

Run these commands for knowing what are the GPIO's already requested in the drivers.

$ mount -t debugfs debugfs /sys/kernel/debug

$ cat /sys/kernel/debug/gpio

2. Please go through this section for details on pin mux settings from software

http://processors.wiki.ti.com/index.php?title=DM816x_C6A816x_AM389x_PSP_User_Guide#Modifying_Pin_Mux_settings

Regards
Anilkumar

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0 B M over 14 years ago in reply to Anil

Prodigy 210 points

Hi Anil,

Thanks for the reply. I did try to follow the instructions in Modifying_Pin_Mux_settings. This is the reason I added the following code:-

TI816X_MUX(SC1_C4, OMAP_MUX_MODE1) in linux-2.6.37-psp04.00.00.10/arch/arm/mach-omap2/board-ti8168evm.c.

I now realise my error. In setting SC1_C4 I thought I was configuring gp0[24] but in fact this is gp0[25]! For gp0[24] I need to set TI816X_MUX(SC1_DATA, OMAP_MUX_MODE2).

I can now change the value on the pin by using ths sysfs interface.

As an aside, the Spectrum schematics are a bit misleading in the name changes from gp0[25] on main board and GP1[12] on daughter, as it passes from processor to jumper 2 on daughter board.

Processor GP0[25] (Pin H4) -> SC1_C4 -> J20.P50 -> SC1_C4 -> GP1[12] -> JP2.P3

Thanks for confirming I was taking the correct steps.

0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

HI ALL

my ezsdk = ti-ezsdk_dm816x-evm_5_02_01_59

kernel coming from the prebuilt-inamges and rootfs = nfs

1> i have no /sys/class/gpio/ director in my system

2> why

3>help thank you

0 Anil over 13 years ago in reply to jim snoopy

TI__Expert 6655 points

Hi Jim Snoopy,

Build uImage with proper kernel configuration. Follow bellow steps for enabling the GPIO sysfs entries

1. make CROSS_COMPILE=arm-none-linux-gnueabi- ARCH=arm ti8168_evm_defconfig

2. make CROSS_COMPILE=arm-none-linux-gnueabi- ARCH=arm menuconfig

3. Enable this GPIO sysfs interface

Device Drivers ---> GPIO Support ---> /sys/class/gpio/... (sysfs interface)

4. Rebuild the kernel and boot the board with new uImage.

Then you are able to see the /sys/class/gpio entries.

Regards

Anilkumar

0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

thank you so much Anilkumar

0 jim snoopy over 13 years ago in reply to jim snoopy

Expert 1070 points

Hi Anil

my ezsdk = ti-ezsdk_dm816x-evm_5_02_01_59

kernel coming from the rebuilt-inamges Following above steps for enabling the GPIO sysfs entries and rootfs = nfs

ti8168evm + vs daughter board

1> i can see /sys/class/gpio entries

2> but I can't change the gpio's value

root@dm816x-evm:/sys/class/gpio# echo 24 > export

root@dm816x-evm:/sys/class/gpio# ls
export gpio24 gpiochip0 gpiochip32 unexport

root@dm816x-evm:/sys/class/gpio# cd gpio24
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# ls
active_low edge subsystem value
direction power uevent

root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat direction
in
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0

root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo "out" > direction
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat direction
out

root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo 1 > value
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0

3> why help?

4> change to use GPIO1-12

5> but GP1[12] pin is still 0V

note : GP1[12] -> vs daughter board -> JP1[3]

6> WHY HELP

thank you so much

0 Anil over 13 years ago in reply to jim snoopy

TI__Expert 6655 points

Hi Jim Snoopy,

Have you taken care of pin-mux configurations? If not, Please go through above posts.

If pin mux configurations are not proper then what you are setting in s/w will not reflect in hardware.

And make sure that you are probing the correct GPIO pin (While checking the voltage of GPIO pin)

As coming to the GPIO sysfs entries, GPIO numbers are starting from 0. Make sure that you are configuring the correct GPIO what you required.

I can say GPIO44 is nothing but 12th pin of GPIO - 1. GPIO0 has 0-31 pins and GPIO1 has 32-63

Run these commands for knowing what are the GPIO's already requested in the drivers.

$ mount -t debugfs debugfs /sys/kernel/debug

$ cat /sys/kernel/debug/gpio

Regards

Anilkumar

0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

hi Anilkumar

1 > in order to operate GP0[24] -> VS daughter -> JP1 -> P1

2 > i have added TI816X_MUX(SC1_DATA, OMAP_MUX_MODE2), to the static struct omap_board_mux board_mux in the linux-2.6.37-psp04.00.00.12/arch/arm/mach-omap2/board-ti8168evm.c

3 > rebuilt kernel

4 > my steps

root@dm816x-evm:~# mount -t debugfs debugfs /sys/kernel/debug/
root@dm816x-evm:~# cat /sys/kernel/debug/gpio
GPIOs 0-31, gpio:
gpio-0   (vgpio 0             ) out lo
gpio-1   (vgpio 1             ) out hi
gpio-2   (vgpio 2             ) out hi
gpio-3   (vgpio 3             ) out hi
gpio-20 (nor                 ) out lo

GPIOs 32-63, gpio:
root@dm816x-evm:~#

root@dm816x-evm:~# echo 24 > /sys/class/gpio/export
root@dm816x-evm:~# ls /sys/class/gpio/
export      gpio24      gpiochip0   gpiochip32 unexport
root@dm816x-evm:~# cd /sys/class/gpio/gpio24
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# ls
active_low edge        subsystem   value
direction   power       uevent
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/class/gpio/gpio24/direction
in
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/class/gpio/gpio24/value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo "out" > /sys/class/gpio/gpio24/direction
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/class/gpio/gpio24/direction
out
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/class/gpio/gpio24/value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo 1 > /sys/class/gpio/gpio24/value
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/class/gpio/gpio24/value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24#

5 > why value is still 0 ?

6> Regards

0 Anil over 13 years ago in reply to jim snoopy

TI__Expert 6655 points

Hi Jim Snoopy,

Could you please checkout the GPIO sysfs status without connecting the VS daughter card to the base board?

Thanks

Anilkumar

0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

hi Anilkumar

root@dm816x-evm:/sys/class/gpio# ls
export      gpiochip0   gpiochip32 unexport
root@dm816x-evm:/sys/class/gpio# echo 24 > export
root@dm816x-evm:/sys/class/gpio# ls
export      gpio24      gpiochip0   gpiochip32 unexport
root@dm816x-evm:/sys/class/gpio# cd gpio24
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# ls
active_low edge        subsystem   value
direction   power       uevent
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat direction
in
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# ls
active_low edge        subsystem   value
direction   power       uevent
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo "out" > direction
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat direction
out
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo 1 > value
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# mount -t debugfs debugfs /sys/
kernel/debug/
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/kernel/debug/gpio
GPIOs 0-31, gpio:
gpio-0   (vgpio 0             ) out lo
gpio-1   (vgpio 1             ) out hi
gpio-2   (vgpio 2             ) out hi
gpio-3   (vgpio 3             ) out hi
gpio-20 (nor                 ) out lo
gpio-24 (sysfs               ) out lo

GPIOs 32-63, gpio:
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# echo 1 > value
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat value
0
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24# cat /sys/kernel/debug/gpio
GPIOs 0-31, gpio:
gpio-0   (vgpio 0             ) out lo
gpio-1   (vgpio 1             ) out hi
gpio-2   (vgpio 2             ) out hi
gpio-3   (vgpio 3             ) out hi
gpio-20 (nor                 ) out lo
gpio-24 (sysfs               ) out lo

GPIOs 32-63, gpio:
root@dm816x-evm:/sys/devices/virtual/gpio/gpio24#

####################### nothing change

Thanks

0 jim snoopy over 13 years ago in reply to jim snoopy

Expert 1070 points

hi Anilkumar

i have test gpio interface in the ezsdk = ti-ezsdk_dm816x-evm_5_02_01_59

from gp0[0] to gp0[31] i can not change thier value

from gp1[0] to gp1[31] all are ok

why ?

thanks

0 Anil over 13 years ago in reply to jim snoopy

TI__Expert 6655 points

Hi Jim Snoopy,

I added this code toboard-ti8168evm.c file

TI816X_MUX(SC1_DATA, OMAP_MUX_MODE2), /* GPIO0_24 */

Then I tested the status on my board and it is working fine with respect to GP0_IO24, see my log

=============================================================================

Arago 2009.11 ti8168-evm ttyO2

ti8168-evm login: root
login[1214]: root login on `ttyO2'

/* Checking the PINMUX settings from kernel, 0x2 means it is operating in mode 0x2 */

root@ti8168-evm:~# devmem2 0x48140b18
/dev/mem opened.
Memory mapped at address 0x40293000.
Value at address 0x48140B18 (0x40293b18): 0x2
root@ti8168-evm:~#

root@ti8168-evm:~# cat /sys/class/gpio/
/sys/class/gpio/export       /sys/class/gpio/gpiochip32/
/sys/class/gpio/gpiochip0/   /sys/class/gpio/unexport
root@ti8168-evm:~# echo 24 > /sys/class/gpio/export
root@ti8168-evm:~# cat /sys/class/gpio/
/sys/class/gpio/export       /sys/class/gpio/gpiochip32/
/sys/class/gpio/gpio24/      /sys/class/gpio/unexport
/sys/class/gpio/gpiochip0/
root@ti8168-evm:~# cat /sys/class/gpio/gpio24/
/sys/class/gpio/gpio24/active_low /sys/class/gpio/gpio24/subsystem/
/sys/class/gpio/gpio24/direction   /sys/class/gpio/gpio24/uevent
/sys/class/gpio/gpio24/edge        /sys/class/gpio/gpio24/value
/sys/class/gpio/gpio24/power/
root@ti8168-evm:~# cat /sys/class/gpio/gpio24/value
0
root@ti8168-evm:~# cat /sys/class/gpio/gpio24/direction
in
root@ti8168-evm:~# echo "out" > /sys/class/gpio/gpio24/direction
root@ti8168-evm:~# cat /sys/class/gpio/gpio24/direction
out
root@ti8168-evm:~# cat /sys/class/gpio/gpio24/value
0
root@ti8168-evm:~# echo 1 > /sys/class/gpio/gpio24/value
root@ti8168-evm:~# cat /sys/class/gpio/gpio24/value
1
root@ti8168-evm:~#

=============================================================================

Could you please verify the same on other board?

I have one question from your last post. did you add all mux configurations for GP[0-1]_IO[0-31] to board file?

Please tell me the kernel version what you are using?

Regards

Anilkumar

0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

thank you so much

Anilkumar

1> my kernel come from ezsdk5.02 added config gpio/sys interface

2> now all are ok

before , i did not execute devmem2 0x48140b18 cmd

root@ti8168-evm:~# devmem2 0x48140b18
/dev/mem opened.
Memory mapped at address 0x40293000.
Value at address 0x48140B18 (0x40293b18): 0x2
root@ti8168-evm:~#

3>now i want to know

why "devmem2 0x48140b18" cmd must be executed ?

what is its functions ?

4>thank you so much

Anilkumar

Regards

0 Anil over 13 years ago in reply to jim snoopy

TI__Expert 6655 points

Hi Jim Snoopy,

That command is for checking the status of PINMUX configurations. Whatever we set from the kernel is exactly reflecting in the hardware or not?

Just for isolating the problem

Regards

Anilkumar

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Please click the Verify Answer button on this post if it answers your question.

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0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

thank you very much Anilkumar

all my problems have been resolved

wish everything go well with you work

see you

0 Anil over 13 years ago in reply to Anil

TI__Expert 6655 points

Hi Jim Snoopy,

Could you please tell me the Kernel version (like 04.00.00.XX) what you are using?

Thanks

Anilkumar

0 jim snoopy over 13 years ago in reply to Anil

Expert 1070 points

i am sorry

Anilkumar

i forgot it

my ezsdk = ti-ezsdk_dm816x-evm_5_02_01_59

kernel source = linux-2.6.37-psp04.00.00.12

my kernel image = come from rebuilded the above kernel

add the config of device -> GPIO -> sys in the kernel menuconfig

thank you again Anilkumar

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GPIO on dm816x-evm