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Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Sun Aug 20, 2017 11:08 pm
by kostbill
Hello. I don't know if this the right place for this topic, so please place it in the correct board if it is not.

I am working on a bluepill and on Sloeber.
I have a 2.8 inches graphic LCD with the ILI9341 controller from buydisplay working with hardware SPI (the latest from Roger's repository).

The problem I am having is that when I update an area of 80x100 pixes, using the drawstring with large numbers (tft.setTextSize(2) and char size 6), the display flickers.

At first, I wrote on top of the previous number, the same number with the background color, and then updated the number and noticed the flicker.
Then, I erased the rectangle area and write the number of top, which I thought to be faster, but it really isn't that much faster.

I tried the "Partial Mode" of the ILI9341, but it only allows for a full segment of rows to be used, for example from row N to row K, which doesn't help because I display other things on the same rows.

Tomorrow I will try Steve's new library, but can anyone also suggest some workarounds?

If there is not good solution I will try the 8 bit mode.

Thanks,
Bill.

Re: [ILI9341] flickering on drawstring on large characters.

Posted: Mon Aug 21, 2017 8:23 pm
by kostbill
I placed a 10 mF cap between the power lines and it seems to be fixed.
It seems to be that the steep current rising on the display is causing the display to flicker.

Re: Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Mon Aug 21, 2017 9:29 pm
by RogerClark
10 milli F ?

That's a a lot.

Re: Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Mon Aug 21, 2017 11:21 pm
by zmemw16
uF ?

Re: Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Tue Aug 22, 2017 1:02 am
by RogerClark
That would be my thought

i.e micro Farad not milli Farad

10 uF isn't that much and it was unclear whether the "fickering" was something to do with the backlight

Its possible that the OP is trying to power the LED though a board which does not have a good enough regulator to supply the LED backlighting

Re: Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Tue Aug 22, 2017 12:17 pm
by kostbill
Yes sorry! I mean milli Farad.

The power supply I am using to power the LCD is from the 5V Arduino Due.

Re: Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Tue Aug 22, 2017 12:26 pm
by zmemw16
and as we have no knowledge of his setup, but could suggest he powers the backlight from another source with only
common ground.
those power supplies that plug into bread boards can usually be set as both outputs to 3v3 or 5v0 or one of each and all from a 7v5 or 9v or 12v walwart psu. i like 7v5 as it's the coolest running one.

maybe take a poll on the most useful hardware setup excluding the UUT/UUD :)

stephen

Re: Solved: [ILI9341] flickering on drawstring on large characters.

Posted: Tue Aug 22, 2017 1:17 pm
by kostbill
Well, I didn't think that it could matter at that time. I know I am not a good electronics engineer :( .