Pi setup is as follows:

  • version 4B
  • 64 bit OS
  • ethernet cable from router to Pi
  • power cable from Pi to laptop USB port
  • SD card 16 GB
  • Router recognizes, lists Pi in devices, can SSH to it

If I move the connection of power cable USB end from laptop to iPhone plug in wall socket, I see power lights, ethernet lights as before on the Pi, but the device isn't listed on the router. Why is this? How do I resolve this?

I have enabled SSH, userconf has username:hash-password, wpa_supplicant.conf as follows:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev

  • 1
    Not enough power?
    – joan
    Jul 9, 2022 at 19:38
  • How do I resolve this? ... simple, don't use the iPhone plug
    – jsotola
    Jul 9, 2022 at 23:34

1 Answer 1


You are suffering from a classic problem of not enough power. Assuming you have 3 cores it needs about 5 watts of power. The Raspberry Pi 4 requires a power adapter that outputs at 3 Amps at 5 Volts. The iPhone will give you 5V at how many watts? There is a reason they recommend minimum capacity form the power supplies, you are experiencing it. If you connect peripherals add the additional power requirement(s) to the power supply requirements. I will say A proper power supply will solve your problem.

USB 2 ports are designed to supply 5V of electricity with a maximum current of 0.5A. This wattage is standard standard across the majority of computers and means the overall power output will be 2.5 Watts at best.

USB 3 ports are designed to provide up to 900mA or 0.9A, which translates into 4.5 watts.

  • Do not keep spreading this misinformation. All models will operate on a decent 1A supply. Even the oldest Apple PS are rated at 5W supply. There is NO "recommend(ed) minimum capacity" See raspberrypi.stackexchange.com/a/51616/8697
    – Milliways
    Jul 10, 2022 at 1:04
  • I agree with @Milliways, it isn't the power (laptop usb ports supply limited current). You are setting up two network connections one wired and one wireless to the same network which is going to cause confusion. Check the output of 'ifconfig' or 'ip addr' when using the laptop and note which adapter(s) has connected and the ip addresses. I would disable the wireless and work with the fixed wire until you have it working. The ethernet port should retain the IP address from the router so you can try pinging it without having to consult the router. Feb 3 at 15:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.