Only a solid red light and no ethernet lights after broken script

Question

Model: Pi 3 B+

I wrote a script using GPIO pins and I'm fairly certain there was no way for it to cause a short circuit. I ran the script, and was unable to stop it using ctrl+c, so I pulled the plug on the Pi and when I tried plugging it back in, all I got was a solid red light. The ethernet lights are also not on when I have an ethernet cable plugged in. I've tried recovering the SD card by reformatting it and reinstalling the saved disk image, and also tried putting a blank copy of NOOBS on it, but it still isn't working. I used a voltmeter to test the GPIO pins, and the 5V is working. The 3v3 doesn't seem to be working, however...

Any thoughts? Do I just need to get a new Pi? I just got this a few weeks ago and would hate to have to redo everything.

Answer 1

If there is no 3.3V the Pi is DEAD!

No script can damage the Pi (although it can corrupt the OS - as can pulling the plug).

NOTE poking a voltmeter at the header pins is a BAD idea. Even it the Pi wasn't dead, a momentary short between the 3.3V & 5V pins (which are adjacent) is invariably fatal.

Answer 2

Question

I wrote a script using GPIO pins and I'm fairly certain there was no way for it to cause a short circuit.

Answer

Well, if you are connecting a GPIO pin to any pin of a 5V powered device, then there is risk of frying the Rpi or shortening it life。 You might like to read the following posts for more details.

DHT11 sensor and the wrong voltage may have fried my RPi3 [Rpi Latching Up Instant Suicide]

Circuit wiring issue [Rpi Latching up Slow Suicide]

Reading Output signal from external circuit using Rpi GPIO Pin

Rpi Latch Up Discussion Notes 1

Rpi Latch Up Discussion Notes 2

Rpi 5V Low Trigger Relay Latching Up Risk Notes

Appendices

Appendix A - Warning on dangerous pulling up GPIO pin to 5V

GPIO Electrical Specifications Raspberry Pi input and output pin voltage and current capability - Mosiac Documentation Web

GPIO pin circuitry

The internal diodes shown in the figure are not really substrate diodes, but they are actually parasitic FETs.

Electrically, their I-V characteristic looks like a diode's, but with a greater forward drop and a more gradual knee.

They may protect against low current transient events caused by transient out-of-range voltages applied to the pins, but they are not intended to protect against the application of voltages greater than the supply voltage or less than ground, even with an external series resistor.

In brief, you should never deliberately forward bias those "diodes".

Consequently, you can not safely place an external pull-up resistor to 5V on the I/O pin. That would forward bias a parasitic FET and owing to its poor internal impedance to the chip's internal power rail it may overheat, or worse, it may bias up parts of the chip to voltages greater than they can handle.

So, don't do it!