Difference between revisions of "Newhaven LVDS Capacitive Display Set"

Revision as of 17:04, 26 July 2022

This section shows information about the Newhaven LVDS Capacitive Display Set. The iMX8M Industrial Development Kit in this configuration is equipped with Yocto dunfell, kernel 5.4 to support LVDS display with a touchscreen layer. In this case the display is installed on the top of the iMX8M Development Baseboard.

Mechanical connection

When combined with the complete iMX8M Industrial Kit, the Display Set creates a compact, ready-to-use solution. To assemble them together, the following mechanical and electrical accessories were designed and selected to be part of the Display set:

TFT LCD 1024x600 Pixels display with LVDS interface and Capacitive Touch with SiS9509 controller
4x Hex Standoff Threaded M3 30.00mm long [Manufacturer PN: 971300321]
40 Position flat flex cable 50.80mm long [Manufacturer PN: 0150200427]
6 pin touchscreen flat flex cable
necessary spacers

Hardware connection

To enable smooth communication between the board and the display, connect the 40 Position FFC cable for LCD and 6 pin touchscreen FFC cable. To implement the display capabilities, following connections need to be made:

connection between LVDS Display and iMX8M Development Baseboard connector LVDS0 NHD (J12) using a 40 Position FFC cable
touchscreen connection between iMX8M Development Baseboard connector NHD Touch (J13) and Touchscreen 6 pin FFC cable

LVDS and Touchscreen cable

Hardware jumpers Newhaven LVDS

Make sure that configurable 0R resistor are moved to Newhaven LVDS0 interface

Software instructions

iMX8M Industrial kit is preinstalled with Yocto dunfell operation system enabling LVDS and touchscreen capabilities by default. Manual configuration is necessary, Devicetree in U-Boot have to by set to NHD LVDS0 LCD.

LVDS0 NHD Devicetree in U-Boot

Manually booting with LVDS interface as a primary source for video output:

Fastboot: Normal
Normal Boot
Hit any key to stop autoboot:  0
u-boot=>
u-boot=>
u-boot=>
u-boot=>
u-boot=>
u-boot=> fatls mmc 0:1
 27787776   Image
    48586   imx8mq-evk-voipac-dp.dtb
    48793   imx8mq-evk-voipac-hdmi.dtb
    49194   imx8mq-evk-voipac-lvds-koe.dtb
    49198   imx8mq-evk-voipac-lvds-newhaven.dtb

5 file(s), 0 dir(s)

u-boot=> setenv fdt_file imx8mq-evk-voipac-lvds-newhaven.dtb
u-boot=> saveenv
Saving Environment to MMC... Writing to MMC(0)... OK
u-boot=>
u-boot=> boot

.

Touchscreen test

Default Voipac iMX8M Image contain evtest utility to catch touchscreen events. Make sure SiS9509 controller is detected and bound as input device. Select the device event number 1 (generic ft5x06 (79)):

root@imx8mq-voipac:~# evtest
No device specified, trying to scan all of /dev/input/event*
Available devices:
/dev/input/event0:      30370000.snvs:snvs-powerkey
/dev/input/event1:      generic ft5x06 (79)
/dev/input/event2:      gpio-buttons
/dev/input/event3:      bd718xx-pwrkey
/dev/input/event4:      Logitech USB Receiver
/dev/input/event5:      Logitech USB Receiver Mouse
/dev/input/event6:      Logitech USB Receiver Consumer Control
/dev/input/event7:      Logitech USB Receiver System Control
Select the device event number [0-7]: 1
Input driver version is 1.0.1
Input device ID: bus 0x18 vendor 0x0 product 0x0 version 0x0
Input device name: "generic ft5x06 (79)"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value    308
      Min        0
      Max     1023
    Event code 1 (ABS_Y)
      Value    211
      Min        0
      Max      799
    Event code 47 (ABS_MT_SLOT)
      Value      0
      Min        0
      Max        4
    Event code 53 (ABS_MT_POSITION_X)
      Value      0
      Min        0
      Max     1023
    Event code 54 (ABS_MT_POSITION_Y)
      Value      0
      Min        0
      Max      799
    Event code 57 (ABS_MT_TRACKING_ID)
      Value      0
      Min        0
      Max    65535
Properties:
  Property type 1 (INPUT_PROP_DIRECT)

Touchscreen events are generated after touching capacitive touch screen.

root@imx8mq-voipac:~# evtest /dev/input/by-path/platform-21a4000.i2c-event 
Testing ... (interrupt to exit)
Event: time 1658851286.1658851286, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value 40
Event: time 1658851286.1658851286, type 3 (EV_ABS), code 53 (ABS_MT_POSITION_X), value 506
Event: time 1658851286.1658851286, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 478
Event: time 1658851286.1658851286, -------------- SYN_REPORT ------------
Event: time 1658851286.1658851286, type 3 (EV_ABS), code 57 (ABS_MT_TRACKING_ID), value -1
Event: time 1658851286.1658851286, -------------- SYN_REPORT ------------