1

My Zynq board has SPI, I2C but does not have kernel level GPIO (The GPIO on the MIO is sent to a bunch of other things) so I can't get it from the headers. Believe me when I say this.

I need some kernel level GPIO so I can drive a touch screen interface. I need to map some GPIO to the stmpe610 touch screen driver (Device Tree compatible = "st,stmpe610"). This is all well and good. So what I want to do is somehow map the I2C to GPIO (which will be connected to the display), and pipe the driver to interface through I2C. This way I can access the GPIO pins of my i2c expander from kernel space.

I looked at the i2c-gpio driver, but it does the opposite of what I want (http://lwn.net/Articles/230571/). It takes GPIO and makes it I2C by bit-banging.

I have an i2c expander mini-board that will take I2C and spit out GPIO. So if I have a gpio-i2C that would be great.

Maybe I have wandered too afar and off the beaten path. Does the stmpe610 have an i2c driver? This would also alleviate my issue.

<<

Xofo
  • 1,256
  • 4
  • 18
  • 33

1 Answers1

3

If I have understood you correctly, you have a GPIO expansion board that you can connect to your Zync main board.

If the above assumption is correct, what you have to do is find the correct driver for your GPIO extension board. What model do you have ? What chip is there on it ? Maybe there is already a driver for it in the kernel. If so, you then just have to declare it under your I2C base controller node in your device tree so that its GPIOs can then be referenced in your device tree for your stmpe610 touchscreen node.

If the chip does not have a driver yet, you then will have to write a GPIO driver for the chip. One good example to start with is the GPIO driver for the MAX 7300, that is connected via I2C as well. Have a look at gpio-max7300.c and gpio-max730x.c

Simson
  • 3,373
  • 2
  • 24
  • 38
Longfield
  • 1,505
  • 1
  • 12
  • 24
  • Thank you. This is a good answer. Can you please provide an example of the i2c to GPIO mapping in a sample device tree. I want to make sure I get the syntax correct. – Xofo Jul 20 '16 at 00:09
  • I found this: http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/gpio/gpio-max732x.txt and this: http://stackoverflow.com/questions/26667082/max732x-c-i2c-io-expander-gpio-keys-w-linux-device-tree-not-working Thanks! – Xofo Jul 20 '16 at 03:59