SK-AM62B-P1: Issue with accessing GPIOs in the User Expansion Header

Rahul Santhosh

Part Number: SK-AM62B-P1

Tool/software:

Hi TI,

I'm using SK-AM62B-P1 running on Debian bookworm. I was trying to set a gpio and get the state of the gpio. but I have some confusions regarding the $gpiodetect and $gpioinfo gpiochipx.

here is the output of the same:

I want to set the 13th pin of the expansion header which is the EXP_GPIO0_42 as per datasheet. Assuming that it is the line number 42 on gpiochip0,
i tried $gpioset gpiochip0 42=1
but the pin state doesn't go high. I have verified that using a multimeter.

I don't think there is an issue with gpiochip2. because i have enabled both the

line 5: "EXP_PS_3V3_En" unused input active-high

line 6: "EXP_PS_5V0_En" unused input active-high

this worked fine, and 3V3 and 5V0 was available on the expansion header. So what should I do in-order to correctly access the gpio through the expansion header?

4 months ago

0 Anshu Madwesh 4 months ago

TI__Genius 12390 points

Hello,

Can you what device tree changes you've made?

You can follow this thread for a reference: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1268671/sk-am62-using-the-gpios-in-the-40-pin-user-expansion-port/4804378

Thanks,

Anshu

0 Rahul Santhosh 4 months ago in reply to Anshu Madwesh

Prodigy 140 points

How do I get access to the DTS files? my /boot directory on have dtb folder. and only have dtbo files. Do I need to create a new dts file and build it to generate dtbo and then add it as a device tree overlay? Is that the correct method?

0 Rahul Santhosh 4 months ago in reply to Rahul Santhosh

Prodigy 140 points

Also, I don't have the k3-am62x-sk-common.dtbo file available in my /boot/dtb/ti folder.

0 Anshu Madwesh 4 months ago in reply to Rahul Santhosh

TI__Genius 12390 points

Hello,

SDK Documentation to build Linux: https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/10_00_07_04/exports/docs/linux/Foundational_Components_Kernel_Users_Guide.html#overview

.dtb files are compiled from .dts and .dtsi sources, so k3-am625-sk.dtb is the compiled dtb you want.

You'll need to change the device tree source file to add support for the GPIO then recompile the .dtb.

Thanks,

Anshu

0 Rahul Santhosh 4 months ago in reply to Anshu Madwesh

Prodigy 140 points

I downloaded the kernal sources and obtained the k3-am625-sk.dts files from it, also the k3-am625.dtsi and k3-am62.dtsi, which are included in it. However I have some issues with compiling the dts file :

the line 10 is the part where some dtsi files are included.

the dtsi files are located in the same folder as the dts file. also the dt-bindings is in the /usr/src/linux-headers-6.1.83-k3-rt/include/dt-bindings .

So, how do I include the dtsi files and resolve this issue?

One more thing, I have found k3-am625-sk-rpi-hdr-ehrpwm.dtbo file in the /boot/dtb/ti folder. Can I use it as overlay in-order to get the rpi header (user expansion header) work?

+1 Anshu Madwesh 4 months ago in reply to Rahul Santhosh

TI__Genius 12390 points

Hello,

You need to develop the AM62x device tree files on your host machine (not your EVM command line) and copying over to the SD card (or whatever boot method).

The main_pmx node in the device tree is what devices the PinMux so Linux will enable the GPIOs. This is found in either k3-am62x-common.dtsi or k3-am625-sk.dts.

The AM62x Linux Academy is helpful: https://dev.ti.com/tirex/explore/node?node=A__AEIJm0rwIeU.2P1OBWwlaA__AM62-ACADEMY__uiYMDcq__LATEST

If you want to use device tree overlays, you'll need to compile it, and follow these instructions: https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/10_00_07_04/exports/docs/linux/How_to_Guides/Target/How_to_test_MCAN_on_AM62x.html#enable-device-tree-overlay

That device tree overlay is meant to enable ePWMs on the RPI header. For other peripherals like GPIOs, you need to configure the main_pmx node.

Thanks,

Anshu

+1 Rahul Santhosh 4 months ago in reply to Anshu Madwesh

Prodigy 140 points

Hi Anshu,

Thank you for your support. This has resolved my issue.

I have another query regarding configuring a GPIO on the user expansion connector as an input interrupt pin. While I know how to set it as an input, I'm unsure about the GPIO address.

For example, in the following line:

AM62X_IOPAD(0x0088, PIN_OUTPUT, 7) /* (L24) GPMC0_OEn_REn.GPIO0_33 */

The address for GPIO0_33 is `0x0088`. How can I find the addresses for other desired pins?

0 Anshu Madwesh 3 months ago in reply to Rahul Santhosh

TI__Genius 12390 points

Hi Rahul,

This thread got lost so apologies for the delayed response.

Please refer to the datasheet Table 6-1 for information about each pin: www.ti.com/.../am625.pdf

Best Regards,

Anshu

Processors

Processors forum

SK-AM62B-P1: Issue with accessing GPIOs in the User Expansion Header