Q:

Arduino Nano disconnecting from PC on plugging in 3.3v NRF24L01 into PCB

I've built this PCB which includes two I2C port expanders, an Arduino nano, inputs for buttons and encoders, and headers to plug in an NRF24L01 board.

Currently, I just have code running to read two encoders plugged into J12 and J11 on this schematic, and send how far each of them have turned over the serial port.

This all works perfectly, the problem comes when I plug in the NRF24L01 into the headers on the board. As soon as I do, the arduino disconnects from the PC; I get the little noise from Windows, both the COM port and the device disappear, and it resets the arduino. However, I can still see the TX LED light up, so the code is still running and the data is transmitting over serial, the PC just doesn't see it anymore. As soon as I remove the NRF board, the nano reconnects and works as usual.
I've tried plugging in an external power source and get the exact same behavior, so I don't believe it's an issue of the NRF drawing too much power. I've tried several different NRF boards as well, so it isn't an issue with the specific board I have plugged in.
What could my problem be?

A:

Nevermind, I'm an idiot. My problem was unrelated to any power issues. I noticed that 70mA seemed much too high for a chip that's supposed to draw 12mA at the absolute most, and after taking a closer look at the PCB, I realized I swapped the two rows of four pins horizontally, so every pin was connected wrong. After wiring it correctly with jumper cables, the problem is solved and the NRF works fine.

