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Backlight PWM frequency.

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Moose

6 Posts

Posted - 19 Oct 2004 : 17:00:28

Is it possible to control the backlight PWM frequency on the Bitsy X system. I have seen in the forums (and with an oscilloscope) that it is currently set to 7.2kHz. However, due to the capacitance of the FET's in our system this is too fast and we need to slow it down to about 3kHz.

akidder

1519 Posts

Posted - 19 Oct 2004 : 18:32:44

You've probably read the details at topic 673 about the PWMs available on our systems.

In particular, on the BitsyX the ADSmartIO (ATMega) microcontroller drives the Vee and Backlight PWMs (using PD4 and PD5). The PWM frequency is hard-coded in the ADSmartIO firmware, so we'd have to spin a special build for you if you needed the 900 Hz PWM output.

One alternative might be to configure PXA255 GP16 ("EIO4" on J10) for PWM operation. That option would give you more precise frequency control. However, we don't have a driver for that functionality, so you'd have to write your own if you wanted it right away.

Let us know how we can best meet your application needs.

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