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Topic: Eastrising RA8875 480x272 SPI Black screen (Read 140 times) previous topic - next topic

TobyOne

Just taken delivery of the above display but am having a few issues. Have connected it up via SPI on my mega (pins 50,51,52,53, GND,VSS) but I get just a black screen. I would expect to see the LCD back lights come on even if I'd got the SPI connections wrong. Have downloaded Eastrisings library and examples. Anybody familiar with this display?


TIA
Chris

TobyOne

#1
May 04, 2019, 09:01 am Last Edit: May 04, 2019, 09:16 am by TobyOne
Nobody? Mr Prentice, I believe that you have had one of these in the past, will it display a white screen when power is supplied or have I got a faulty one? it has jumper 8 set for 5 volts. Just need to know if this is duff so I can stop wasting my time trying to get it working. I have contacted East Rising but they have not replied yet.

david_prentice

You will destroy a 3.3V chip if you  use 5V logic.

BuyDisplay provide Adapter Shields for punters who have 5V Arduinos.
They also provide documentation for those punters that are too mean to buy the Shield.

David.

TobyOne

Ah..so even though the board is configured to run off 5 volts and I'm using the SPI bus I still need a shield?

david_prentice

A Shield makes life easier.   But you can do the level-shifting yourself if you want.

They provide a document that explains how to connect 3.3v controllers to 5V logic.

The average Arduino punter ignores advice.   It does not matter with a Red ST7735 board.   If it does not work they have not wasted much money.
BuyDisplay are more expensive.   You do not want to throw it away.

David.

TobyOne

I suspect then that I've screwed this one as I would expect the backlight to come on when powered up, which it doesn't. Yes, that was an expensive mistake  :( Oh well, so if I use a 3.3v Arduino and SPI bus I won't need the shield? If not I could use something like a TXS0108 to shift the levels, I couldn't find the documentation on their website about level conversion.

ZinggJM

#6
May 04, 2019, 12:44 pm Last Edit: May 04, 2019, 01:58 pm by ZinggJM
@TobyOne,

I don't know if your display uses this feature, but the RA8875 has a backlight control and power save feature. So the backlight might be off until the controller has been set up. I don't remember the details with my Waveshare 7" 800x480 RA8875 display, but this is a code snippet from init:

Code: [Select]
 /* Clear the entire window */
  writeReg(RA8875_MCLR, RA8875_MCLR_START | RA8875_MCLR_FULL);
  delay(500);
  writeReg(RA8875_PWRR, RA8875_PWRR_NORMAL | RA8875_PWRR_DISPON);
  writeReg(RA8875_GPIOX, 1);
  writeReg(RA8875_P1CR, RA8875_P1CR_ENABLE | (RA8875_PWM_CLK_DIV1024 & 0xF));
  writeReg(RA8875_P1DCR, 255);
No personal message please; any question may be useful for other users. Use code tags for code. Make links clickable with URL tags. Provide links to the product in question.

TobyOne

Thanks ZinggJM, I'll have a look later but since I've been pumping 5v down the SPI bus I'm assuming the worst.

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