I2C-GPIO Expander driver support for AM3517EVM

Steven Kane

Other Parts Discussed in Thread: AM3517

Hello,

I am trying to access the GPIO on the I2C Expander and I saw this commit to the Linux kernel: http://www.mail-archive.com/linux-omap@vger.kernel.org/msg22017.html. I am using a Zoom AM3517 EVM Development Kit from Logic PD: http://logicpd.com/products/development-kits/zoom-am3517-evm-development-kit and the TI Software Development Kit for AM35x processors: http://focus.ti.com/docs/toolsw/folders/print/linuxsdk-am35x.html. My question is: how do I access the GPIO on the I2C Expander from C/C++ user land using the I2C Expander driver? High speed access is preferred.

Thanks,

Steven Kane

over 15 years ago

0 Vaibhav Hiremath over 15 years ago

TI__Expert 8180 points

Hi Steven,

As you can see from the patch, the I2C expander is registered as a standard GPIO chip to Linux GPIO library (Sub-system) so all the standard interfaces which Linux provides to access/control GPIO pins can be used here. Please refer to the Linux documentation for more information on GPIO, I have copied link to the GPIO kernel documentation below -

http://www.mjmwired.net/kernel/Documentation/gpio.txt

Search/Look for "Sysfs Interface for Userspace" in this link.

Please let me know if you face any issues or need any further details on this.

Thanks,

Vaibhav

0 Aaron Ridinger over 14 years ago in reply to Vaibhav Hiremath

Intellectual 490 points

Hi Vaibhav,

I just came across this post as I am trying to access the I2C Expander GPIO as well through the Userspace. How do I know the GPIO numbers on the expander to export so that I can use them? Or do I even need to know the number?

Thanks,

Aaron

0 Norman Wong over 14 years ago in reply to Aaron Ridinger

Guru 26430 points

Try looking in "/sys/class/gpio/" for gpiochip directories. The files in those directories have details on GPIO number and a label that sometimes hints at what the controller is. Eg.
cat /sys/class/gpio/gpiochipN/base
cat /sys/class/gpio/gpiochipN/label
cat /sys/class/gpio/gpiochipN/ngpio

0 Aaron Ridinger over 14 years ago in reply to Norman Wong

Intellectual 490 points

Thanks, that was exactly what I needed.

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I2C-GPIO Expander driver support for AM3517EVM