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Frank N. Furter
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Joined: 28/05/2012
Location: Germany
Posts: 1133

Posted: 06:19pm 06 Jul 2026

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Perhaps my report here will be useful to other PicoCalc users as well.

Some of you may have noticed my issues with the PicoCalc. After I installed newer beta versions, the device would only turn on sporadically. At first, at least the V22 seemed to run stably (coincidence?). I had equipped my PicoCalc with a Pico2. After I replaced it, the problems seemed to disappear for a short time. But then even the V22 stopped working.

Frustrated, I set the device aside for the time being and checked it with an oscilloscope yesterday. Okay, after turning it on, the voltage at VSYS fluctuated a bit, but it was still within normal limits. To me, all the signals looked the same during both a successful and an unsuccessful boot attempt.

So I asked ChatGPT about my problem. Since my PicoCalc has been working fine for about half a year now and I haven't made any changes to it, ChatGPT also suggested that something on the circuit board might have aged.

ChatGPT suggested that I trigger the QSPI CLK signal at power-on. In fact, no signal was present there during a failed boot attempt. ChatGPT concluded from this that the firmware couldn’t possibly be involved at that point and that the error was likely due to the power supply. ChatGPT says that the RP2350 is more sensitive to voltage dips than the RP2040, and even small glitches can cause the Pico to hang during bootup. ChatGPT says that these glitches can be so brief that it would be difficult to see them with my oscilloscope.

ChatGPT told me to remove the display and the CF card. In fact, the device often turned on successfully when the CF card was removed. Now I was supposed to solder a 22-47 µF capacitor between VSYS and GND on the Pico.
I had a 22 µF electrolytic capacitor on hand. After I soldered it in, my problems were gone! The PicoCalc started up 25 times in a row without any trouble.

I'd already had the feeling that Clockworkpi had skimped on the capacitance on the board. It does indeed seem that the device was built very tightly to spec. Either a capacitor has actually aged, or it has sustained some other kind of damage.

The fact is that the PicoCalc is currently running stably with the additional electrolytic capacitor, and I haven't had any problems with the current release version either. Without ChatGPT, I wouldn't have found a solution so easily.

It remains to be seen whether this capacitor will actually solve the problem in the long run, or whether there is some other damage somewhere that is causing this capacitor to be necessary in the first place.

Frank

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