Zedboard Oled Petalinux

[Ilesar]

Hi,

I'm new in the world of embedded linux and i want to create a program to write words on the Oled display on zedboard. I use Petalinux 2018.2 and apparently the oled driver is not there by default. So i added the drivers created by digilent https://github.com/Digilent/linux-digilent/blob/86b46b6606eea44c59af56b732e5393f2eb0adce/drivers/staging/pmods/pmodoled-gpio.c in a petalinux module.

But now i want to use the functions defined by the driver in a application in order to use later a TCP server to get the words to display in the oled by another device. But i can't made the link between the driver and the application.

Am i using the wrong method ?

Somebody can help me ?

 

[Ionel]

Have you issued petalinxu-config --get-hw-description=/path/to/hdf/directory ?

[Ionel]

For that driver you need AXIGPIO not the pmodoled IP. If you do not use the driver(which is obsolete) the pmodoled IP will be accessible in user-space via uio (libuio). And for this you can find examples in many other projects.

[Ilesar]

14 hours ago, Ionel said:

 

I don't find the answer in this topic, i think it miss few messages.

[Ionel]

 

[Ilesar]

Thanks for your time !

I replaced &gpiops by &gpio0, apparently it is the only one that made the device tree compile, ( otherwise i got system-top.dtb: ERROR (phandle_references): Reference to non-existent node or label "gpiops") but i still have the sames errors that in my previous message when i launch petalinux. I see in the documentation that there are two examples with differents pin numbers. Where i can find the right one for my design ?

 

Thank you !

[Ionel]

Also notice that PmodOLED IP has no IRQ so none should be specified in device tree.

You can find the parameters for pmodoled node here

Pmods were removed in commit: 3953cedd78464cab

[Ionel]

/include/ "system-conf.dtsi"
/ {
};

&PmodOLED_0 {
	compatible = "dglnt,pmodoled-gpio";
	/*other prameters you need to adjust excpt reg*/
};

your system-user.dtsi should look like this.

[Ilesar]

yes it does, there is the pl code :

/ {
	amba_pl: amba_pl {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "simple-bus";
		ranges ;
		PmodOLED_0: PmodOLED@40000000 {
			compatible = "xlnx,PmodOLED-1.0";
			reg = <0x40000000 0x10000 0x40010000 0x1000>;
		};
	};
};

 

[Ionel]

Was the pmodoled-gpio@e0010000 added in pl.dtsi ?

[Ilesar]

Okay, i found the syntax error, it was the "pmodoled-gpio_instance: " witch shoudn't be there. But now, how do i find the correct values to set in the node ? Is it with Vivado ?

Furthermore, i got this when i launch petalinux :

pmodoled_gpio: loading out-of-tree module taints kernel.                        
platform spi_gpio.2: spi_busnum_to_master(2) returned NULL                      
pmodoled-gpio zed_oled: add_gpio_pmodoled_device_to_bus failed: -38             
pmodoled-gpio: probe of zed_oled failed with error -38  

Could you help me ?

Thanks.

[Ilesar]

Yes i did, this is the command i used :

$ petalinux-config --get-hw-description=~/external_mux/external_mux.sdk

[Ilesar]

Thank you,

I implemented the the pmod oled ip in the following project :

but when i write the node in system-user.dtsi, following the module readme, i got an error in compilation ( the value are set random for now as i don't know how to find the good ones) :

/include/ "system-conf.dtsi"
/ {
		pmodoled-gpio_instance: pmodoled-gpio@e0010000 {
			compatible = "xlnx,pmodoled-gpio";
			reg = <e0010000 0x1000>;
			interrupt-parent = <&intc>;
			interrupts = < 0 26 4 >;
		};
};

Do you known where that come from ?

Thank you in advance.

[Ionel]

Yes in system-user.dtsi you will add your node or changes to the node.

For application you will need to read write from file (character device file provided by the driver in /dev/)

 

[Ilesar]

Thanks,

i will try that. The device tree file i need to modify is system-user.dtsi, right ?

For the application c code, will i need to add something (like an include) or will the functions of the driver be defined by default ?

[Ionel]

After you add the pmod oled IP in vivado project.

Then you set petalinux project to use the new  hdf(includes bitstream).

Then you need to add a node for it in the device tree to load this driver.

[Ilesar]

Thank you for your anwer, I got :

root@oled:~#  lsmod | grep gpio
pmodoled_gpio 16384 0 - Live 0xbf000000 (O)

but only after i launch insmod with the path you gave me, otherwise lsmod display nothing.

[Ionel]

For insmod you need to provide the path to .ko.

If the module is somewhere under /lib/modules/{kernel-vesion}/ it may already be loaded.

Please post output of this command.

lsmod | grep gpio

[Ilesar]

I got : insmod : can't insert 'pmodoled-gpio.ko': no such file or directory.

[Ionel]

what is the output of lsmod ?

[Ilesar]

Thank you for your answer,

the module is build, i have the .ko file, but the driver don't seems to be loaded into the board.

 

 

[Ionel]

Have you managed to build the module(search for it in /lib/modules/ )?
Did the driver load? (check boot log or dmesg for "PmodOLED display driver")