OLDI Display

There is a known issue with the device tree in the BSP-Yocto-TISDK-AM65xx-ALPHA1 release where the LCD-018 display is not properly enabled. Please see the Known Issues page for more information and a workaround. 


The phyCORE-AM65x Carrier Board provides support for an OLDI LVDS display through the connector X24, which is comprised of an LVDS signal connector (white) and a power connector (red). These connectors support various PHYTEC LCDs, such as the LCD-018-070-KAP.

The development kit also provides a touch controller (STMPE811) at U39 and interfaces the resistive touch panel typically integrated into an LCD. Communication to and from this touch controller is accomplished with I2C and its device address which is configurable via the J8 jumper.

See the end of this guide for further information regarding advanced touch controller configurations.

This guide explains how to connect an OLDI LVDS display to the phyCORE-AM65x development kit and access it in Linux.

Materials

  • Display LCD-018-070-KAP

Step-by-step guide

Setting up the Display

Display Switches

  • There is a switch labeled "S1" on the back of LCD-018 where the backlight can be set to either: "always on", "always off", "PWM", or "potentiometer" (there is a potentiometer on the display labeled R30). In order to control the backlight via the phyCORE-AM65x as described in this guide, this switch needs to be set to PWM which corresponds to | off | off | on | off |.

Display Switch 1

Display Switch S1

  • There is a switch labeled "S2" on the back of the LCD-018 that specifies the I2C address of the EEPROM onboard the display. To ensure the address of the display EEPROM doesn't conflict with any other devices on the same bus (RTC and EEPROM on the SOM) this switch needs to be set to | on | on | off | on |.

Display Switch S2

  • With the board powered off, connect the display to the connector on the phyCORE-AM65x Carrier Board as shown in the picture.

    phyCORE-AM65x Development Kit Connected to Display

  • Power on the phyCORE-AM65x and boot into Linux. (You may need to calibrate the LCD). An application will start. 

    Displayed Powered On

Controlling Display Backlight

The backlight brightness of the display is controlled by a PWM and can be configured via Linux sysfs. 

  • Read current brightness: (Expected output is a numeric value between 0-7)

    Target (Linux)
    cat /sys/class/backlight/display_backlight/brightness
  • Set "brightness" to values 0-7, with 7 being the brightest. For example:

    Target (Linux)
    echo 7 > /sys/class/backlight/display_backlight/brightness
  • Set bl_power to turn backlight off/on. Valid values are 0-4:

    0= FB_BLANK_UNBLANKbacklight fully enabled
    1= FB_BLANK_NORMAL
    2= FB_BLANK_VSYNC_SUSPEND
    3= FB_BLANK_HSYNC_SUSPEND
    4= FB_BLANK_POWERDOWNbacklight powered down
  • Use the following command to check the state of the backlight: 

    Target (Linux)
    cat /sys/class/backlight/display_backlight/bl_power

    The backlight is on by default:

    Expected Output
    root@am65xx-phycore-kit:~# cat /sys/class/backlight/display_backlight/bl_power
    0
  • Poweroff the display:

    Target (Linux)
    echo 4 > /sys/class/backlight/display_backlight/bl_power
  • Power the display back on:

    Target (Linux)
    echo 0 > /sys/class/backlight/display_backlight/bl_power

Not seeing the display brightness change? Ensure you have the switch "S1" correctly set on the back of the LCD. See the above warning regarding the display switch settings.

Display Touchscreen

The LCD-018 has an onboard capacitive touch screen controller that is controlled by the phyCORE-AM65x via I2C. You can use the touchscreen to interact with the application running on the display. This section provides some additional information on the touchscreen implementation in Linux.

  • By default, input0 corresponds with the touchscreen controller in the phyCORE-AM65x Linux BSP. However, if additional input devices have been added, this could be different. Confirm that the name of input0 matches the touchscreen controller's with the following command: 

    Target (Linux)
    cat /sys/class/input/event0/device/name
    Expected Output
    root@am65xx-phycore-kit:~# cat /sys/class/input/event0/device/name
    EP0700M09

    We can see here that the name of the input0 interface is named "EP0700M09".

  • Use the input-events command to print out additional information when the touch screen is pressed:

    Target (Linux)
    input-events 0
    Expected Output
    /dev/input/event0
       bustype : BUS_I2C
       vendor  : 0x0
       product : 0x0
       version : 0
       name    : "EP0700M09"
       bits ev : EV_SYN EV_KEY EV_ABS
    
    waiting for events
    18:02:52.959948: EV_ABS ??? 0
    18:02:52.959948: EV_ABS ??? 297
    18:02:52.959948: EV_ABS ??? 855
    18:02:52.959948: EV_KEY BTN_TOUCH pressed
    18:02:52.959948: EV_ABS ABS_X 297
    18:02:52.959948: EV_ABS ABS_Y 855
    18:02:52.959948: EV_SYN code=0 value=0
    18:02:52.965230: EV_ABS ??? 294
    18:02:52.965230: EV_ABS ??? 852
    18:02:52.965230: EV_ABS ABS_X 294
    18:02:52.965230: EV_ABS ABS_Y 852
    18:02:52.965230: EV_SYN code=0 value=0
    18:02:52.979243: EV_ABS ??? 292
    18:02:52.979243: EV_ABS ABS_X 292
    18:02:52.979243: EV_SYN code=0 value=0
    18:02:52.993009: EV_ABS ??? 851
    18:02:52.993009: EV_ABS ABS_Y 851
    18:02:52.993009: EV_SYN code=0 value=0
    18:02:53.006912: EV_ABS ??? 291
    18:02:53.006912: EV_ABS ??? 852
    18:02:53.006912: EV_ABS ABS_X 291
    18:02:53.006912: EV_ABS ABS_Y 852
    18:02:53.006912: EV_SYN code=0 value=0
    18:02:53.020058: EV_ABS ??? 289
    18:02:53.020058: EV_ABS ??? 856
    18:02:53.020058: EV_ABS ABS_X 289
    18:02:53.020058: EV_ABS ABS_Y 856
    18:02:53.020058: EV_SYN code=0 value=0
    18:02:53.025591: EV_ABS ??? -1
    18:02:53.025591: EV_KEY BTN_TOUCH released
  • Use CTRL + C to cancel the print command


 Advanced Touch Controller Configurations

Touch Controller Solder Jumper Configurations


J8

1+2 (Default)Sets the U39 LVDS Touch Controller I2C address to 0x82
2019-07-02_20-10-32_Display Connectivity (X24)
2+3Sets the U39 LVDS Touch Controller I2C address to 0x88