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Brightnes adjustment of Midas 7' 1024x600 display

tjam

Hi

Does anyone know how to adjust the back-light of the Midas MCT070HDMI-B-RT display?

I am using these on Raspberry with Rasbian.

It would like to turn the display off without interrupting the attached Raspberry PI.

 

The data sheet does not reveal any info about this.

 

regards

tjam

  • Best I can see on the datasheet is to make use of gpio 18 (Back light Enable). this is probably under software control right now but there may be a way ?

  • in reply to Robert Peter Oakes

    Thanks, the gpio 18 at 1 will turn off backlight and 0 will turn it on. This info was not available in data sheet at the Farnell item catalog.

    The backlight is very strong when on, so I will check some more to see if it is possible to adjust it. The "xbacklight" does find the display.

    Any tip is most welcome....

    tjam

  • Hi Torgeir,

     

    I know nothing about the display you're using, but the alternative raspberrypi.org 7" capacitive display has driver control for brightness. You may wish you check whatever driver you're using, to see if there is also control in a similar or slightly different way. For example, check /sys/class to see if backlight exists, and try to see what paths are there. With the raspberrypi.org display, control would be as follows:

    echo xx > /sys/class/backlight/rpi_backlight/brightness

    where xx is a value between 0 and 255 (255 is brightest).

     

    If you do not have such a thing, you may wish to load a device tree fragment file to try to do it using pulse-width modulation (PWM). For instance, see here for a list along with a paragraph explanation for each one:

    https://github.com/raspberrypi/firmware/tree/master/boot/overlays

    You can see one there called hdmi-backlight-hwhack-gpio which might meet your needs.

    Again, I've never used this so you're going to have to experiment I think..

    If you don't get anywhere with drivers, try PWM from (say) Python code. If that works, then you could always have it running as your own user-space service, rather than a real driver. A bit of effort, but there's a chance it may be good enough.