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I have a new Raspberry Pi 4 and Sense HAT. I've installed Raspian Buster installed via SD-card and managed to boot headless with ethernet cable connected. Power is from a USB-C cable plugged into a wall outlet. So far so good.

However, as soon as I attach the Sense HAT, the machine freezes:

  • LEDs display permanent rainbow
  • green disk activity light stops
  • pi won't connect to the network

There doesn't seem to be anything in the logs, the machine just freezes.

What could this possibly be due to?

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    Ah, le me see. (1) Sense HAT takes big current, (2) Rainbow screen usually means power supply voltage too low, much lower than 4.8V. (3) 1 and 2 means Sense HAT overloads your weak power supply. (4) Use a bigger power supply (5V 3A eg )might solve the rainbow screen problem. Good luck and cheers.
    – tlfong01
    Mar 27 '20 at 6:11
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    Thanks for the input! I've updated the question to explain that I'm drawing power from a USB-C cable, plugged into a wall outlet.
    – Bruce Becker
    Mar 27 '20 at 6:33
  • What happens if you plug in the hat before the boot?
    – SkyPlayX
    Mar 27 '20 at 6:38
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    I'm drawing power from a USB-C cable, plugged into a wall outlet that's how you power the pi4 ... what the power rating for the power supply
    – Jaromanda X
    Mar 27 '20 at 6:43
  • @PradhyumnaNarain - the same thing as described before. It's a standard Italian 240/60Hz I think.
    – Bruce Becker
    Mar 27 '20 at 7:12
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The problem was the display resoluton. I found the solution in this github issue:

$raspi-config

7 Advanced Options

A5 Resolution

DMT Mode 4 640x480 60Hz 4:3

Since this Pi4 is booted headless, I needed to set the display resolution.

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  • I am glad to hear yourself solved the problem. I was feeling that the problem was complicated. So I googled and came to the quick conclusion that it should be a early release buster bug, most likely fixed in a late release. "Buster won't boot headless with the Sense Hat attached - rpi.org.forum 2019jun28": raspberrypi.org/forums/…. Cheers.
    – tlfong01
    Mar 27 '20 at 8:14
  • yes, I saw that. I tried a couple of things which would probably turn up here and on the forum, but only this change solved my issue.
    – Bruce Becker
    Mar 27 '20 at 9:07
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    Yes, actually I was about to point out another possible cause related to your power supply. You mentioned that you power supply is an "USB-C cable, plugged into a wall outlet". But there are two types of power supplies with USB-C connector: (1) Wall wart power supply with 5V, 3A output, (2) "Charger" to charge smart phones etc. This kind of charger might only output 2A or 2.5A maximum, no problem to charge smart phones, but too weak for Rpi4B.
    – tlfong01
    Mar 27 '20 at 9:15
  • Unfortunately, I don't have a multimeter with me, but I can confirm that the power supply was not the problem.
    – Bruce Becker
    Mar 27 '20 at 9:21
  • Yes, of course you have already solved the problem. And we don't usually use a multi-meter to do accurate currents measurements. We usually the read spec at the bottom side of the wall wart. But they are only rough numbers. Eg, if it says 5V 2.5A. then no current load voltage might be 5.5V, but drops to 4.5V when drawing 2.5A.
    – tlfong01
    Mar 27 '20 at 9:33

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