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6 years, 8 months ago.
Another White Screen
Hello Firstly I would like to thank you for creating this library for the RA8875, I have high hopes for what I can do with it in the future, however before that can happen I will need to solve this problem.
Upon power up I am met with a white screen and nothing else, I have two screens which are both setup for 4 wire SPI, one is 5V and the other is 3.3 V, both are 4.3" WQVGA.
I have tried several of the example programs you have made available with the same result for each one, my own attempts at writing code have been equally unsuccessful, the SPI pins on the LPC1768 I am using also appear to be working as it can communicate with the LCD on the mbed application board through the same pins (p5, p6, p7, p12). All solder blobs appear correct.
I have noticed through probing with an oscilloscope that there is no data being transmitted on any of the pins for both boards, all 4 pins are held high at 3.3V.
I have exhausted all paths I can think of right now, if you have any suggestions they would be much appreciated.
Ryan
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1 Answer
6 years, 8 months ago.
hi Ryan,
Sorry I didn't spot this sooner - I didn't get any auto-notification email...
So, let's start with your LPC1768 and the 5v version of the display. That should exactly match what I have.
Next, part way down the RA8875 Based Display page, is my wiring "example for 4 inch Display". Hopefully, you can wire it exactly like that.
Next, let's think about your power source. You're probably powering it all from your PC or Laptop. Some USB ports are lower power, and some may be marked as higher power. I'd suggest the higher power if you have both. As a test, I'm running for an unlabeled USB port on my laptop, and my demo program won't start reliably. I updated the lcd.init( ) function to start with the backlight at about 50% brightness, and now it starts 100% of the time. I'll update the minimum sample on the RA8875 Based Display page with those details.
Next, the software. I just did a few quick checks, and there is some sensitivity to the version of mbed. I have done very little with mbed os 5, because of the RAM memory footprint increase. Using mbed2 v146, it works. Using a newer mbed lib, the lcd.printf() function is not working properly. Graphics objects appear to work ok.
Update: Immediately after writing this, I tried to update the component page. While I was the original author, I'm now greeted with a denial. I've sent an appeal to the mbed team.
In the meantime, try minimum sample, or try changing your init( ) line to:
lcd.init(480,272,16,100);
This sets the screen size, and the color depth (to 16 bits per pixel), and it turns the display on to a little under 1/2 brightness (100 out of 255). If your PC USB port isn't willing to provide enough power at 100%, this may be the solution.
Many Thanks for your Reply, I can confirm Mine was wired exactly as yours was and that I have tried powering it from a laptop USB, PC USB and regulated 5V from a bench PSU.
I will try what you have suggested as soon as possible and report back on what I find.
posted by 26 Aug 2017Hello again, I have done as suggested with much more success, reverting to version 146 seems to have done the job, there has been no repeat of the white screen of death so far, in fact i have struggled to repeat it intentionally. I will keep playing around with it for a while and see what happens.
one little side note, in your RA8875_Demo example code the for command in line 40 did not work until i included a int before the i >> for (int i=0; i<=30; i+=5)
Thanks for your help once again and I look forward to using the RA8875.
posted by 27 Aug 2017