RA8875 with 7'' Touchscreen
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RA8875 with 7'' Touchscreen

by King_John on Wed Mar 07, 2018 9:43 am


I recently purchased the RA8875 driver board along with the 7" 40-pin TFT display. When running off my bench power supply at 5v, the backlight just flashes for brief moment, then nothing happens. The 'Lite' pin has no affect on this behavior. Another user has asked this same question (1), but hasn't gotten a response. I'm wondering if I need to turn up the voltage to VIN to kick the screen on, but I'm not about to fry a board I just got and waste money. Another user has asked this as well (2), and hasn't gotten a response. In this forum post (3), an Adafruit rep says the board is meant for 3.3v - 5v only on the VIN pin. In this post (4), the same rep says it's ok to use between 8v-9v. Can someone please answer these questions, update the incorrect threads, and update the product page so nobody else has to go through this wild (spam filter wouldn't let me use the word g00se?) chase? I'm a huge fan of Adafruit products and typically don't require support, but this product is lacking basic info that you typically provide with other custom boards like this one.

1. viewtopic.php?f=47&t=122273&p=610386
2. viewtopic.php?f=47&t=130729&p=649864
3. viewtopic.php?f=31&t=113786
4. viewtopic.php?f=25&t=97037&p=487585

Posts: 3
Joined: Tue Oct 15, 2013 5:47 pm

Re: RA8875 with 7'' Touchscreen

by iPostHuman on Thu Apr 12, 2018 10:10 am

I am having the same issue. I am using the FT232H breakout board (p2264) with a 5V breadboard supply. My 7" display also just flashes briefly and then nothing. I have checked that I am sending the correct SPI protocol (mode0) and command/data protocol using my Logic analyzer (with a decoder enabled) and I clearly see all the commands being sent to the device--except that the RA8875 board never answers back on the MISO line.
Also, I am not using any other slave just the RA8875 and I even dropped the CLK down to 1MHz.
I even double checked using my DSO and the signals look clear and within tolerance.

I know my FT232H board works fine because I have driven several different SPI displays with it: 128x128 oled, 128x128 TFT, 320x480 TFT and Max7219 leds.

I think my RA8875 board is defective. Up to this point everything I have purchased from Adafruit has worked like a champ. This device seems dead in the water, the irony being it was supposed to be the simplest of the drivers.

Posts: 2
Joined: Mon Feb 19, 2018 2:06 pm

Re: RA8875 with 7'' Touchscreen

by King_John on Sun Apr 15, 2018 1:31 am

Hey iPostHuman,

After a bit of time I ended up contacting the support department via email (through the webform on the returns page I believe). They simply directed me back to the forums, refusing to RMA the product without troubleshooting first. They noted that they'd contact the tech support forum reps to get on this case. As you likely guessed, this never happened. I had to reverse the charge with my credit card company. After a quick inspection of other boards, it appears that the reps only answer questions about more general things like LED's and Relays. Unfortunately, this means that there is a hole in the process for returning products such as ours.

Side note, I ended up powering the screen/board on ~9v from a bench power supply. The backlight did come on, though the screen never displayed anything, despite my best efforts. I also was able to see that my MCU was communicating properly, but the RA8875 simply wasn't replying to anything.

Posts: 3
Joined: Tue Oct 15, 2013 5:47 pm

Re: RA8875 with 7'' Touchscreen

by achanpicarro on Wed Apr 25, 2018 5:07 pm

I have purchased (12) HDMI 4 Pi - 7" Display 1280x800 (720p) IPS - HDMI/VGA/PAL/NTSC for my customer in Germany. One of the display is defective. How can I get a replacement display for my customer? I have sent photos of the back and side of the display. I am unsure how the photo of the front of the blank display will help my customer to get his replacement display. The customer checked the instruments DVI interfaces and made a crosscheck with another display. He was sure that the display is out of function (also the internal menu is not visible!).

1. Model is HDMI 4 Pi - 7" Display 1280x800 (720p) IPS - HDMI/VGA/PAL/NTSC. Picarro purchase order number is PO3567.
2. You have clear photos for the back and side of the display. My customer said that serial number that does exist on display.
3. There is no software issue.
4. There is no trouble with a code sketch
5. The customer is not building a project.
HDMI 4 Pi - 7in Display 2.jpg
HDMI 4 Pi - 7in Display 2.jpg (41.44 KiB) Viewed 8 times

Posts: 1
Joined: Wed Apr 25, 2018 4:52 pm

Please be positive and constructive with your questions and comments.