iMX51EVK backlight control

[martinhowell]

The Backlight control on the iMX51EVK is connected to pin DI1_D1_CS, the BSP just sets this up as a GPIO and turns the backlight on and off with this pin, however it seems it is possible to use this pin to provide some kind of PWM control to vary the backlight brightness. Has anyone doen this or can shed any light on it?

[mbp]

We did the same thing (standard PWM Backlight output control pin) and that was that works great (except our 9v-IN supply had a bit of ripple resulting in visual noise on the LCD so we switched to a more clean & stable 5v source to eliminate that).

[martinhowell]

Well in the end we just moved the backlight control pin onto a standard PWM output from the CPU on our design, and it works just fine there. (In fact possibly better, we had previously done a design with the iMX25 using the provided contrast PWM line on the LCD interface and it was a very granular control).

[mbp]

Looking into this as well.  The CLAA070* LCD provided with the Display board - has the backlight hardwired ON and the PWM is (appears) disabled as it's in a steady-state.  The Android OS still provides the backlight adjust but obviously no PWM output.  We are activating Backlight support and will be looking into where and why the PWM is 'disabled'.  

If you've discovered anything, please post it here so later this week when we get to it - we can share info.  Thanks!