1

refereing to Adjusting the Brightness of the Official Touchscreen Display

I had success adjusting the back light power and brightness on one system, but trying the same commands on another RPi the brightness is entirely "binary", values < 128 are off and >=128 are on.

Am I missing something?

thanks,

Just tried a 100% vanilla raspbian jessie lite image and the results are still "binary". On a 2B.

The working hardware is 2B, Linux kivypie 4.1.19-v7+ #858 SMP Tue Mar 15 15:56:00 GMT 2016 armv7l GNU/Linux

Community
  • 1
Dave Lawrence
  • 165
  • 1
  • 7
  • 1
    Could you give us some differences between the Pi's use are using? – Darth Vader Jun 14 '16 at 17:47
  • Hi, I don't have access to the original hardware any more, but I know it was a 2B, runinng the kivypie 0.8 image based on Jessie. I have the other system in front of me. It's a 3B also kivypie 0.8, jessie, just updated to 4.4.11-v7+. I can probably get access to the original system in the next few days. – Dave Lawrence Jun 14 '16 at 17:57
  • please can you tell me what information would be useful to collect to work out what is the significant difference. Thank you. – Dave Lawrence Jun 14 '16 at 19:25
  • I can't say for certain, but I'd bet that there's something weird going on with your distribution. – Jacobm001 Jun 14 '16 at 21:54

1 Answers1

3

A Problem With the Version

Depending on when you purchased your official Raspberry Pi display, you either own Version 1.0 or Version 1.1.

Judging from the specific nature of your error (values < 128 are off and >=128 are on), I am almost entirely certain the problem you're facing is that you own the Version 1.0 model of the official Raspberry Pi display. That version does not support brightness control - it only turns the display on or off. To summarize brightness control between Version 1.0 and Version 1.1:

Version 1.0: Setting the brightness, or n, to anything between 0-127 is "off" and anything between 128-255 is "on".

Version 1.1: Brightness adjustment works properly between 25-255, as you would expect. A word of warning: "Unless you have a remote connection to your Pi, or really know what you're doing then don't set the backlight brightness below 20 or turn the power off. It's not easy to type when you can't see!" - Phil Howard, a Pimoroni Forum moderator

As far as I know, this was a fix that the team designing the official Raspberry Pi display implemented at Version 1.1. This is the simplest reason I have to explain why brightness control is not available in Version 1.0 but available in Version 1.1.

Beyond just my personal experience with the product, I tried looking around for some official documentation to support my answer. All I could find was some relevant discussion of this bug in the official Raspberry Pi Forums.

Checking Which Version You Own

The words "Raspberry PI Display V1.0" or "Raspberry PI Display V1.1" are printed right next the Raspberry Pi logo on the display.

Tweaking Version 1.0 for Adjustable Brightness

Unfortunately, I could not find any legitimate foolhardy approaches to making the brightness adjustable beyond the binary "on" / "off" that is implemented in Version 1.0.

The best solution is to purchase a new Raspberry Pi display module: the ones on sale are >= Version 1.1.

Community
  • 1
Vladislav Martin
  • 148
  • 5