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I am powering raspberry Pi using GPIO no 2, 4, and GND as recommended. The Pi only shows RED constantly ON led and does not boot. However, if I connect the USB power source it boots up. The power supply designed is strict 5V and max 3A.

Furthermore, once the Pi is all booted up and the USB is removed it keeps working fine and even reboots perfectly. Only when I remove the battery and connect again it does not turn on as if it was shut down.

Any hints on where to look?

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    \$\begingroup\$ What does "I am powering my Pi from 2.4.GND gpios" mean? \$\endgroup\$
    – Transistor
    Apr 5, 2021 at 14:19
  • \$\begingroup\$ Updated for calrity \$\endgroup\$ Apr 5, 2021 at 14:47
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    \$\begingroup\$ Post a pic of your setup, could be that the jumper wires/connections are much worse than that of an USB cable. \$\endgroup\$
    – Wesley Lee
    Apr 5, 2021 at 15:08
  • \$\begingroup\$ Pins 2, 4 and GND are not GPIO. GPIO stands for "general purpose input / output". Pins 2, 4 and GND are the power connections, not inputs or outputs. That's what confused me. A further edit required, I think. You might want to specify which version of the Pi you're using and link to its datasheet. 'Raspberry' gets a capital 'R' as it's a brand name. \$\endgroup\$
    – Transistor
    Apr 5, 2021 at 15:29
  • \$\begingroup\$ Regarding the Raspberry Pi, "All models require a 5.1V supply" - Power Supply. Can you tweak the 5 V to 5.1 V? \$\endgroup\$ Apr 5, 2021 at 16:07

1 Answer 1

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There are two 5V. TP 1-3 is the input 5V from the mini-usb power connector. The other 5V (the usb 2.0 /3.0 port power) is hardware controlled by the regulator and turns it on after it sends a power good logic to the cpu and receives a clock signal from the cpu. Pins 2&4 should be less than 1 ohm (continuity) between pins them and tp1, tp2, and tp3 located on the bottom side of the board. If your battery is not above 4.63V it will not power up. Usually people will use a low drop out regulator in this circuit. That might be the issue. The only other thing that would be different from powering this from a battery is the usb current sense circuit, that goes back to pin 21 on the circuit. I don't know the logic behind them using that pin, as I seen it grounded most of the time in the tablets that use the MXL7704 regulator. But it shouldn't stop it from running. Low battery voltage will. On the side note, I still don't understand why they didn't put a power switch in circuit, since it is only 5 resistors and a pin header to make that circuit. Here is the schematics they provided (partial). https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematics/rpi_SCH_4b_4p0_reduced.pdf

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