So I got my picocalc yesterday, and there’s a weird issue where there’s this bright vignetting around the edges of the display. I originally though I had to display in too tight, but even with the back cover completely unscrewed its still there. It gets worse the longer its turned off, and gets better the longer its turned on, so after like 15 minutes of being on its basically gone, but if I have it off for a similar amount of time, it comes right back. Did I just get a faulty display or is this a known issue with a fix?
I have four PicoCalc ordered at different times during 2025 and none of them have that look. you might have gotten a bad display, but that’s just a guess on my part.
I ran into the same issue—there’s a noticeable halo effect around the edges on medium gray backgrounds, which gradually fades back to normal after the device runs for a while. According to my research, the mounting method causes physical stress on the screen edges; as the device stays on and warms up, the tolerances change slightly, allowing the liquid crystal molecules to return to their normal operating state.
It really seems to come down to low screen quality. (I’ve also noticed distinct horizontal crosstalk, checkerboard flickering caused by pixel inversion, and temporary image retention after displaying static content for too long—all classic flaws of cheap LCD panels).
The issue isn’t more widely reported simply because most people are using black backgroud,which hides it pretty well.
That’s definitely a flaw with that lcd; I’d suggest contacting Alex and getting a replacement, it’s cheap and fairly quick. The likelihood of getting two displays in a row with this same flaw is pretty low.
(and beapig, it’s not “all units do this but most people don’t see it” - it being less visible on your one faulty unit when displaying black does not say anything about the majority of displays in circulation. And there is no significant stress on the panel when correctly installed; don’t confuse that with the fact that it’s unfortunately easy to incorrectly install it.)
How do I make sure I didn’t install it incorrectly? Like I’m pretty sure it’s in there right, it feels right and matches the picture in the manual but is there a chance I did this to myself?
Based on previous posts here on the forum, installing it incorrectly usually results in a cracked/broken display (and has happened to a lot of us), and that looks different from what you’ve shown here. So I’m not sure if there’s a way to install it and not break it, but still warp it or apply pressure in some way to create this effect you’re seeing.
I agree with @beapig on the image retention – I’ve seen that myself. It only happened once, and that was because I left something on the display for a long time and when I started using it again I saw the burn-in. It eventually went away, but for a little while I thought I’d have to live with it or get a new screen. I’ve been a bit more careful since to not leave something on the display for a very long time if I’m not actively using it. Not sure if it’s relevent, but my PicoCalc was one of the ones from the earliest batches (not the first, but possibly the second, as I ordered it when announced, but I know at least one shipment arrived before mine.) That first screen got cracked, but I installed the replacement within about a month of the arrival of the original order. I’m not sure if they’ve been using the same screen for all shipments since the beginning – at one point Alex said they were going to ship with a different screen when so many were breaking, but maybe the tape fix was enough and all the screens are still the same?
I’m just guessing here since I’m not a hardware guy, but is it possible the screen halo is caused by ambient temperature being too hot or too cold, or some kind of power (battery) issue? Unlike the uConsole, the PicoCalc doesn’t require much in terms of battery so I doubt that could be it, or there would be other issues like device resets, etc. But maybe the reason it takes time to warm up is because it’s literally warming up?
Image retention will happen if the display is unexpectedly powered off while still displaying an image - the charge gets trapped in the display. But it’s not burn-in - it’s only charge and is guaranteed to dissipate, if slowly. That you saw it after displaying the same image for a while is purely a coincidence. All LCDs regardless of price/quality/manufacturer do this, it’s only by taking explicit steps are taken during power-down to display black first that it is essentially hidden - and sometimes it doesn’t happen properly.
That’s not exactly what’s happening with this border fading issue, which isn’t really image retention. It’s still trapping charge, but it’s not an intentionally displayed image which is inadvertently left in place, it’s the panel being actively driven incorrectly which unbalances it, and the edges are more likely to show this first. That could be because the panel itself is out of spec and isn’t behaving appropriately to a correct drive signal, or the panel driver chip (part of the lcd module) is faulty, or the connection to the system is bad (seriously, check that you’ve got the lcd ffc cable squarely and fully inserted into the connector), or the system driver is misbehaving, or the power to the panel is insufficient.
As someone who has developed hardware using panels at all levels of complexity professionally, I’ve seen this a lot. Sometimes it’s even my fault 
In general, if it’s transitory, it’s not likely to be a panel problem, but in this case where we’ve got plenty of examples of the hardware working properly and a couple where it’s consistently bad - those two instances are likely to be either bad panels or bad installations.
i vaguely remember something about the power control registers of the LCD - the way a lot of drivers just copy the initialization commands from other drivers it’s possible the voltages aren’t quite right for the panel the picocalc ships with. i’ve definitely seen more and less halo on mine in different firmwares made with different driver codes
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I’ve been having the same issue, reduced a bit after releasing some tension on the screws, but still present
I have been lurking around the forums and spent way too much time reading the ST7365P datasheet (the ST7796S too in case it was a better match but so far all information was borderline identical, but I digress)
I’ve noticed a lot of discussion about the proper way to run the LCD, but so far I’ve seen a lot of contradicting information and a lot of fragmentation on the drivers, so it wouldn’t really surprise me if gamma, dimming or the automatic brightness control thing could be the culprit, maybe even the brightness itself from the st32f.
The thing that worries me is that it going away after using it for a bit but reappearing after being off for a while apparently could also be a sign of delamination of the layers of the display (which changes how the surrounding backlight LEDs refract inside)
At the same time, a bit of bleeding around the edges in IPS screens is always gonna be there, especially with dark backgrounds
Ah, that’s interesting to know. Makes a lot of sense. I had observed this with mine after leaving a static image on the display for a while, so now my shutdown command briefly clears the display, then all white then all black before powering down.
I don’t know if that’s any better than simply clearing the screen, but it has a sort of “feel-good” factor to me.
Thanks,
-Gordon