Hello. My Pico explorer base LCD is not working anymore. Is there a schematic I could use to debug it?
I don’t see one published or linked too. The Pinout will tell you what pins on the PICO header, and the other header (SPI) are used for the display.
Pin 25 is MOSI
Pin 24 is SCLK
Pin 22 is CS
Pin 21 is DC
There will also be a ground and either VBUS (5V) or 3.3V used for power.
Do you or have you had anything hooked up to the SPI pins on the other header?
Have you tried a different PICO?
Does it not work at all, is the backlight on?
Any error messages when you run your display code?
I plugged the LCD in another Pico explorer base and it works fine. I also plugged the Pico board in another base board and it also works fine. I have nothing else plugged in. When I reset the Pico I can see the LCD go black and then comes back with random pixels. I can see other parts near the LCD. I suspect one of them might have failed.
Is this the built in LCD? If yes, it sounds like the screen part has failed some how?
Yes, the ST7789 LCD on the board. I connected it to another Pico explorer base board and it’s fine so it’s something on the board between the LCD and the Pico.
Bummer, if it had been the screen it would be easier to fix. You can get that screen as a breakout. It would be worth buying one to get another screen to swap in.
Being the driver your into reflow work etc. If you can figure out what failed?
I should be able to reflow or swap components. The LCD connector is a bit tricky, the pins may wick the solder all the way into the connector. There is a 6 pin part near the LCD connector. I can read GEE on it. Does anyone know what part this is?
I have no idea what it is? That’s one issue with IC’s getting smaller and smaller, especially SMT stuff, no room to write much of anything useful on them.
Maybe one of the engineers sees this can can answer please?
I do believe @hel is staff? Phil is for sure @gadgetoid, he’s more on the software side of things though.
There is a contact us link on the bottom of the Shop page. You can e-mail Pimoroni directly via that link. No guarantees on them actually giving you a full schematic though.
I just need to identify that part. That would be good enough I think.
Interestingly 1.3" SPI Colour Square LCD (240x240) Breakout – Pimoroni has the same “GEE” IC, still no schematic for this one either.
Explorer Base schematic is available here.
The six legged component is indeed the LCD backlight driver - it’s an AP2502. If it’s that component that’s failed (we’d suggest checking input voltage on the AP2502 first, to see if that gives any useful clues to what’s going wrong) then it might be replaceable if you have a hot air station and experience with SMD soldering. If diagnostic/repair attempts fail email us at support@pimoroni.com (or via the link on the shop page) and we’ll do what we can to help :)
Thank you @hel for sharing the schematic. Yes, that does look like the backlight driver. The backlight seems to be fine, I can see ramdom pixels being lit up. It looks like the SPI CLK frequency is high, around 65MHz. I suspect I just need to wash my board with some isopropyl alcohol.
Yes, thank you @hel. I concur, doesn’t sound like a backlight issue to me. I have no idea what to check, but if it was the backlight that failed I’d expect it to just not light up.
Thank you both for your help.
My board sat in a drop of water and almost completely coroded the MISO pin. If I bridge the gap it all works fine.
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