Porting small OLED display to i.MX6ULL 14x14 Evk

[mannsikchung]

I'm using i.MX6ULL 14x14 Evk. 

I succeeded to build Yocto and my evk can boot-up.

Now, I want use small OLED disaply.

My small OLED display is SSD1306.

I found kernel driver code in below path

"linux-imx/drivers/staging/fbtft/

I connected it to ECSPI4 as below picture with help of my H/W member.

Resolution is this OLED is just 128x64. 

Can I use this with "core-image-sato" with X11 ? Or should I choose other bb?

I need to draw some image and text in various font.

How can I enable this display?

Device tree need to be modified? Or, Kernel need to be modified?

I have no idea to start porting this.

Any information needed. Thank you.

[mtx512]

Once you have the SPI interface enabled in the kernel, you should be able to write a test program from userspace program to verify the OLED is working before using the framebuffer. FYI I have SSD1306 running on imx6sx but using the cortex m4 via SPI.

[chaunguyenngoc]

Sorry but my knowledge is short. 

I thought SPI interface enabled since I ran "fbtft_device" success &  /dev/fb0 is created.

But can you help more specific about that

Jas Math wrote:

Once you have the SPI interface enabled in the kernel, you should be able to write a test program from userspace program to verify the OLED is working before using the framebuffer. FYI I have SSD1306 running on imx6sx but using the cortex m4 via SPI.

[mtx512]

If you disable FBTFT via menuconfig (ie don't use it), then the spi interface should be available as a linux device ie something like /dev/spidev1.4 . You can then use the linux spi ioctls to open and transmit commands/data to the SSD3106 directly. This way you can verify the spi interface and display work. For SPI see example mxc_spi_test1.c in imx-test-5.3.

[chaunguyenngoc]

Thank you. I get it.

[alexishernandez]

Hi Mannsik, what configuration will you use?, that breakout can be used with either spi or i2c interface. From that picture i notice that you're mixing the SPI and I2C pins (at least that you've modfified the IOMUX config), if so, verify your connection first.
You can use the i2c interface (spi maybe needs to be activated through menuconfig), and do some tests from userspace  using the console with a HDMI monitor.. Using the i2ctools you can see if your display is connected and send it test commands see this.
The next step would be a kernel module, see more info.

[mannsikchung]

Thank you Alexis

I connected it to ECSPI4. And, I2C pins will be used as GPIO for D/C and Reset. 
So, I can not test with i2ctools which you mentioned. Any similar tool to do test over SPI?

BR.

Mannsik

[alexishernandez]

Hi Mannsik

I haven't use it yet but maybe you can utilize the spidev driver, see the Documentation, the driver could be disabled from the kernel, if it is the case you can activate it from the menuconfig.

Here i left some links that may be helpful.
Using SPI w/Linux

Enable SPIDEV for all SPI using i.mx6 (Thread)
Driver extensive description

Best Regards.

[mannsikchung]

To enable this I added some in device tree as below.
In file "imx6ull-14x14-evk.dts"

&iomuxc {

    pinctrl-names = "default";

    pinctrl-0 = <&pinctrl_hog_1>;

    imx6ul-evk {

...

        pinctrl_ecspi4: ecspi4grp {

            fsl,pins = <

                MX6UL_PAD_ENET2_TX_CLK__ECSPI4_MISO   0x70a1

                MX6UL_PAD_ENET2_TX_ENi__ECSPI4_MOSI    0x70a1

                MX6UL_PAD_ENET2_TX_DATA1__ECSPI4_SCLK 0x70a1

                MX6UL_PAD_ENET2_RX_ER__ECSPI4_SS0     0x70a1

            >;

        };

...

};

...

&ecspi4 {

    pinctrl-names = "default";

    pinctrl-0 = <&pinctrl_ecspi4>;

    status = "okay";

};

...

And added my boardname "tarta-tt" and some code as below.
In file "fbtft_device.c"

{

        .name = "tarta-tt",

        .spi = &(struct spi_board_info) {

            .modalias = "fb_ssd1306",

            .max_speed_hz = 16000000,

            .mode = SPI_MODE_0,

            .bus_num = 4,

            .platform_data = &(struct fbtft_platform_data) {

                .display = {

                    .buswidth = 8,

                },

                .gpios = (const struct fbtft_gpio []) {

                    { "reset", 30 },

                    { "dc", 31 },

                    {},

                },

            }

        }

    },

And enabled some feature in menuconfig as below to enable SSD1306 OLED display.

--> Device Drivers
  --> Staging drivers
    --> Support for small TFT LCD display modules
      --> <*> FB driver for the SSD1306 OLED Controller
      --> <M> Module to for adding FBTFT devices

Build was successful. But, when I do modprobe spi_busnum_to_master returns NULL.
I tried busnum option from 0 to 4, but all of try returns NULL as below.

root@imx6ull14x14evk:~# modprobe fbtft_device name=tarta-tt busnum=3

fbtft_device: module is from the staging directory, the quality is unknown, you have been warned.

fbtft_device:  SPI devices registered:

fbtft_device:      74hc595 spi32766.0 100kHz 8 bits mode=0x00

fbtft_device:  'fb' Platform devices registered:

fbtft_device:  spi_busnum_to_master(3) returned NULL

fbtft_device: failed to register SPI device

modprobe: ERROR: could not insert 'fbtft_device': Invalid argument

root@imx6ull14x14evk:~#

Please help me to enable SSD1306 for display.

[mannsikchung]

And one more thing, I enabled SPI_SPIDEV feature in menuconfig.

Best Regards.

Mannsik

[alexishernandez]

Hey Mannsik

Sorry for the late response, i've been really busy this days. I think that maybe you're loading the fbtft module before the spi-bus controller, i don't have the i.mx with me so i can't verify the exact directory but you could try to insert the spi controller module before the fbtft in /etc/modules-load.d/fbtft.conf .

Best Regards.

[mannsikchung]

After I modified ecspi4 section in dts as below
SPI3 is working.

&ecspi4 {
   fsl,spi-num-chipselects = <1>;
   pinctrl-names = "default";
   pinctrl-0 = <&pinctrl_ecspi4>;
   status = "okay";
};

fsl,spi-num-chipselects = <1>;

should be added.

And now, I can test framebuffer with below command.

# fb-test -f 1 -p 0

Thanks.

BR.

Mannsik

[chaunguyenngoc]

Hi Mannsik

Can you tell me how can you get these value:

1. value "0x70a1" in your code below

===

...

        pinctrl_ecspi4: ecspi4grp {

            fsl,pins = <

                MX6UL_PAD_ENET2_TX_CLK__ECSPI4_MISO   0x70a1

                MX6UL_PAD_ENET2_TX_ENi__ECSPI4_MOSI    0x70a1

                MX6UL_PAD_ENET2_TX_DATA1__ECSPI4_SCLK 0x70a1

                MX6UL_PAD_ENET2_RX_ER__ECSPI4_SS0     0x70a1

            >;

        };

===

2. the number "30" , "31" in code below

===

                    { "reset", 30 },

                    { "dc", 31 },

===

[mannsikchung]

The value 0x70a1 is for SW_PAD_CTL_PAD_XXX registers.

[chaunguyenngoc]

Thank you. I see it. 

I'm stucking in OLED display (Oled C click) with imx7s (WARP7) by FBTFT driver.

I think it will have same procedure to boot up. 

But in final result, can you run OLED display with imx6ull by FBTFT driver only after enable SPI & run "modprobe fbtft_device...." ?

[mannsikchung]

Yes I enabled OLED.
After enable the fbtft driver and then add the device name in /etc/X11/xserver-common .

"tarta-tt")

  ARGS="$ARGS -screen 128x64@180"

  DPI="100" ;;

And in some case you need to modify /etc/X11/xorg.conf

to select correct frame buffer in section "Device"

Option "fbdev" "/dev/fb0"

[chaunguyenngoc]

I think you used "core-image-sato" , is it right ?

[mannsikchung]

Yes, I used core-image-sato for the first time. 

And could enable OLED-Display. 

Currently, I'm woking on my own bb based on core-image-sato. 

BR.

Mannsik

[igorpadykov]

Hi Mannsik

one can use it with "core-image-sato" with X11 but driver for that lcd

should be included in image. May be useful to start with uboot logo and below links may help

How to use SPI slave within U-Boot? 

GitHub - mkschreder/hack-ssd1306-openwrt: Tutorial on how to connect an ssd1306 oled display to Open... 

Best regards
igor
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[mannsikchung]

Thank you for your informative reply.

But, I think Kernel code is quite different from the U-Boot implementation.