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Author Topic: BT816 Screen Refresh  (Read 6883 times)

Redeye

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BT816 Screen Refresh
« on: August 13, 2020, 04:08:36 PM »

I have a VM816C50A dev kit with 5" screen which I've hooked up to my XMOS processor via SPI and seems to be working apart from one thing. I've got the display initialised and drawn some text on the screen without any problems, but after a few seconds the screen gradually fades to white or blanks out. I can stop it doing this by writing the same screen to the BT816 once a second, but I'm obviously missing something really basic somewhere that describes how often and why you need to do this. I'd assumed (obviously wrongly), that once I'd written a screen to the BT816 it would stay on screen until I told it to draw something else.

Can somebody point me in the direction of what I'm missing please?
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BRT Community

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Re: BT816 Screen Refresh
« Reply #1 on: August 14, 2020, 09:10:25 AM »

Hello,

Your assumption was correct as you can send a screen to EVE and it will persist until you draw the next screen or power down etc.

You should not need to re-send your display to refresh the screen unless you want to change the screen content.

What does your MCU/SPI bus do once you have sent the screen? Does the SPI remain completely idle or are you performing other operations (even to other SPI devices if they share the same lines with different chip select)?

If you stop sending any SPI commands after the screen is complete and displayed, does it make a difference?

Also, ensure the chip select is de-asserted when not taking to the BT816,

Best Regards, BRT Community
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Redeye

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Re: BT816 Screen Refresh
« Reply #2 on: August 18, 2020, 09:57:01 AM »

Thanks for your advice. The mistake was mine because the processing thread which owned the SPI port was exiting and it looks like that was causing strange things to happen to the SPI port. When I keep the thread running in a while() loop, as it would be in an application, everything is fine.

Thanks again for the help.
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