Developers guide

Chapter 5: Backlight
Backlighting
Psion Teklogix Mobile Devices SDK Developers Guide 29
5.1 Backlighting
The Mobile Devices SDK provides functions that control the display and keyboard backlights on
Psion Teklogix computers. The intensity of the backlight and the conditions under which it is acti-
vated can be queried and set using the SDK.
To conserve battery power, you can configure the backlights to switch off or dim to half intensity
after the computer has been inactive for a selected length of time. The following diagram shows
how these times are related:
The last device activity is one of the following:
• A key is pressed on the keyboard.
• The touchscreen is pressed.
• The scanner trigger is pressed.
• Data is received from the host.
If the computer is operating with external power, you can configure the backlights to remain on at
all times.
5.1.1 Thresholds
On Psion Teklogix computers with ambient light sensors (7530 & 7535), there is a threshold value
that specifies the light level at which the backlights will turn on. The values for the display and
keyboard backlight thresholds are configured independently.
Threshold values are integers between 0 (zero) and 100. A value of 0 ensures that the selected
backlight is always off. A value of 100 ensures that the backlight can turn on at all lighting levels.
Intermediate values control the level of ambient light at which the backlight turns on. The lower
the value, the darker it must be before the keyboard backlight can turn on. Regardless of the
threshold settings, the backlights will only come on if there is activity to trigger it, such as a key-
board or touch screen event.
5.1.2 Timeouts
Using the Mobile Devices SDK, the backlight on-times and dim-times can be set to any positive
integer within the range of the parameter (typically 0 to 2147483647, measured in milliseconds).
However, when setting the values using the Control Panel, the choices are limited to a handful of
predetermined values presented in a drop-down list.
Full intensity
(on-time)
Half intensity
(dim-time)
Off
Last device activity
Time