How to read keys from USB keyboard on AT91SAM9260

Linux and Unix-Like Linux
1

Hi Everyone,

I am using 2.6.26.3-olimex kernel(Embedded system) running on AT91SAM9260. I am using a Logitech USB keyboard.

It is detected as "/dev/input/event0".

I don't know how to detect key press events and read the keys?

Why can't I read the keys using scanf() like funtions?

Can anyone help me?

Regards,
Siva

2

Your embedded system's kernel may not have been built with keyboard support, being an embedded system...

3

Thanks for your response.

I have enabled the following options in the menuconfig file while building uImage.

Input Device Support --> Event Interface
Keyboards --> AT Keyboard
HID Devices --> USB Human Interface Device support
HID Devices --> PID device support
Special HID Drivers --> Logitech and Logitech force feedback

After booting the kernel, USB key board detected as "/dev/input/event0".

I don't know why I can't use this as stdin?

Am I missing some thing here?

4

You're getting closer. :slight_smile:

What kernel version? What options may depend on it. In my kernel at least, 2.6.27, you also need the <*>Generic Input Layer, under Input Device Support in Device Drivers.

5

I have enabled Generic Input Layer, under Input Device Support in Device Drivers.

But still I can not use USB key board as stdin.

Have I missed something else?

6

I'm reaching the limits of my knowledge here, I'm not sure how Linux decides what keyboard device to use with what physical terminal device. I do know that the keyboard does not literally become stdin -- that'd be an easy fix if it did, but the event interface reports raw key codes, not actual keystrokes. Instead linux pairs a physical keyboard with some sort of physical output device in order to create a terminal device to interact with.

I don't know what programs your embedded system actually has. I don't know what your embedded system actually is beyond what processor runs it. Your system may just not be configured to use it. The content of /etc/inittab, and the complete listing of /dev/, might be useful to figuring this out.

It'd also help if you replied more than once every three weeks.

7

Thanks for your response.

I am using AT91SAM9260 controller with Linux 2.6.30.4 kernel.

I have attached my /etc/initab/ entries and /dev/ entries.

Please have a look into them and share your views.

8

Well, your inittab makes one thing clear... Your system creates one and only one terminal, hardwired to the serial port and nothing else.

I don't know of any straightforward way to attach your keyboard to it instead, though, for a couple reasons:

  • A keyboard is not a terminal. You cannot write data to a keyboard. You need to somehow multiplex two things into one device here.
  • You could easily brick your machine here by messing up the primary terminal. Does it by any chance have a second serial port?

I've been looking for a way to multiplex two things into one device. Nothing yet. It might be necessary to create a pseudo-terminal device yourself and emulate it.