How to get rid of the blink­ing rain­bow square on your Rasp­berry Pi pic­ture frame

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Do you have a slow­ly flash­ing 1 cm rain­bow square in the top right cor­ner of your Rasp­berry Pi pow­ered dig­i­tal pic­ture frame? This is your computer's way of say­ing that there is a prob­lem with the pow­er sup­ply. Here is how to fix it.

It hap­pened one day

A few years ago, I built two iden­ti­cal dig­i­tal pic­ture frames with a Rasp­berry Pi 2B+. I used a Rydges 2A/5V pow­er sup­ply which came with a four-star Ama­zon review aver­age and an attached mini USB cable.

About three years lat­er, I noticed a col­ored square in the upper right cor­ner of the screen, which on occa­sion, fad­ed in and out very soft­ly. It was about a cen­time­ter in size. Then it was gone for weeks, came back for a few min­utes, and was gone again.

I start­ed think­ing that my screen was about to expire. As there was no reg­u­lar­i­ty to the appear­ance of the mul­ti-col­or square, and I had nev­er come across a sim­i­lar issue, I was clue­less first.

But, as always, a lit­tle Inter­net research will go a long way.

It turned out that the com­mon­ly called rain­bow square was an under­volt­age warn­ing. It meant that the pow­er sup­ply did not pro­vide the required pow­er any­more. The sig­nal is trig­gered at 4.75V.

But why was every­thing fine for three years and then with­out any hard­ware or soft­ware change, from one day to the oth­er, it wasn't?

The slow and painful death of pow­er sup­plies

The answer is that pow­er sup­plies can lose pow­er over time. The good ones are not sup­posed to, but I guess the $10 USB pow­er sup­plies for our Rasp­berry Pi are not exact­ly rat­ed mil­i­tary grade and can dete­ri­o­rate over time.

Inter­est­ing­ly enough, the oth­er dig­i­tal pic­ture frame which I built at the same time and with the same com­po­nents also start­ed to dis­play the same symp­toms a few months after the first. So it wasn't an iso­lat­ed inci­dent.

When read­ing up on the sub­ject, I found that pow­er sup­ply degra­da­tion is often the result of high tem­per­a­tures and a per­for­mance reduc­tion of about 20% is not unheard of.

The pow­er sup­ply was glued to the met­al back of the bare dis­play, but the IPS dis­play did not get very warm, and nei­ther did the pow­er sup­ply. But it didn't get a lot of ven­ti­la­tion either.

What I found inter­est­ing was the grad­u­al­i­ty of the degra­da­tion. We are used to dig­i­tal com­po­nents, either work­ing or not, but my pow­er sup­ply was fight­ing death for almost six months.

At first, I saw the rain­bow square appear only a few short sec­onds, then noth­ing for weeks, and then a few times dai­ly. In the end, it stayed on per­ma­nent­ly.

By the way, dur­ing all these months, I didn't notice any oth­er tech­ni­cal issue with my Rasp­berry Pi. Every­thing was work­ing as before.

How to fix it the right way

Should your Rasp­berry Pi dig­i­tal pic­ture frame show the same symp­toms, then it's time for a new pow­er sup­ply.

But choose wise­ly as the Rasp­berry Pi pow­er require­ments have increased with the lat­est mod­els.

While the Rasp­berry 2B+ was hap­py with 2A, the lat­est mod­el from June 2019, the Rasp­berry Pi 4 demands 3A.

But it's not just the pow­er sup­ply. It's also the cable.

In my case, the cable with a mini USB plug was firm­ly attached to the pow­er sup­ply, so I did not have a choice.

How­ev­er, should you get a pow­er sup­ply with a detach­able cable, don't skimp on the cable. The thick­ness of the cable is prob­a­bly a good indi­ca­tion of its qual­i­ty. You can lose a lot of per­for­mance with a bad cable. How­ev­er, unlike a pow­er sup­ply, I don't think a pow­er cable will degrade over time.

How to wing it

If every­thing else works fine and it's just the rain­bow square which keeps appear­ing in your pho­tos, then you may be able to pro­lon­gate the remain­ing life of your pow­er sup­ply by telling your Rasp­berry Pi to ignore under­volt­age and stop pes­ter­ing you about it.

A dig­i­tal pic­ture frame is no mis­­­sion-crit­i­­cal appli­ca­tion (although my wife and sis­ter would beg to dif­fer) so you can try the fol­low­ing:

ssh into your Rasp­berry Pi

ssh@your-IP-address

Then

cd /boot/
nano config.txt

Go to the end of config.txt and add the line

avoid_warnings=1

Save, reboot, and the rain­bow square should be gone.

Mind you, if you expe­ri­ence strange behav­ior with your Rasp­berry Pi, then it is indeed time to get a new pow­er sup­ply. You will be sur­prised how many "unex­plain­able" issues can be traced back to an inad­e­quate PSU.