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I am hoping to get some advice, below is the hardware I am using,

Initial power tests, I see that my modem can draw nearly 350 mA during Tx/Rx, and the whole system (processor, hat, modem) is drawing approx. 500 mA during that time.

At idle (no modem activity) it is nominally 185 mA, please see below. This power draw is the processor, USB hat and modem at idle The zero is the sole source of power via the micro USB from an Adafruit DC power supply.

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Two problems occasionally occur,

  1. The USB Hub itself powers off, the red LED, RJ45 port and modem LEDs are not illuminated - I have yet to probe the rails on the Hub, but this is quite indicative its become unmounted(?)
  2. Only the modem powers off, the power LEDS are not illuminated.

This project tends to run headless so I haven't spent a great deal of time seeing the logs, it also happens so sporadically its hard to see in real time. Could someone advise where to check to see if this is a power issue or some other hardware issue? Looking into lsusb or dmesg | grep USB comes to mind, not sure what I should look for.

Unplugging and re-plugging always works. I think rebinding the drivers may be a solution, if a certain error message is stated in the lsusb or dmesg log.

Cheers.

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Checking the published information your Pi can draw just about 3 watts. Pi = 580mA, Modem = 350mA, Other items ???, Total = 930mA Minimum. USB depending on version could supply from 500mA to 1A unless type C. Knowing there are some pulse loads that you are not measuring (meter cannot respond that fast) I would suggest it is your power supply is not capable of supporting this load. You need at least 3 amps, 3 or more would be great.

Your statement: "The USB Hub itself powers off, the red LED, RJ45 port and modem LEDs are not illuminated - I have yet to probe the rails on the Hub, but this is quite indicative its become unmounted(?) " also indicates that it is over loaded.

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  • Thanks for the reply, I am using a Joulescope that has nanosecond resolution. I see the Tx/Rx transmissions, etc. My 2A power supply, seems capable enough, since I am only drawing about 550mA maximum, (120mA from Pi, peripherals 80mA and modem 350mA).
    – Beaker
    Jul 7, 2022 at 13:52

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