Why does my MacBook Pro provide 5 V out via USB-C to micro-USB cable but not via USB-C to USB-C cable?


I’m working on an electronics project where I’m programming a microcontroller via a USB cable connected to my M1 Macbook Pro 2020.

I’ve been doing this fine via a USB-C to micro-USB cable, where the micro-USB end connects to the custom electronics I’m building.

I just got some USB-C breakout boards, which are just pin maps from a female USB-C port to jumper pins (no chips or logic in between), and switched out my micro-USB port for the new USB-C port. I then switched to a USB-C to USB-C cable. I connected the C-C cable from my computer to my electronics and -> nothing.

During the troubleshooting, I found that when I connect the USB-C cable to my computer and one of the breakout boards and check the voltage across VCC and ground, I get nothing:

A digital multimeter showing a 0.00 reading lies on a desk next to a laptop. The multimeter’s probes are connected to a small USB breakout board attached to a USB cable, which is plugged into the laptop. A hand holds one probe near the circuit board, with cables and a padded surface visible in the background.

And to sanity check, I did the same from my USB-C to micro-USB cable to confirm I do indeed get the ~5 V I expect:

A digital multimeter on a desk displays a DC voltage reading of about 5.18 volts. The meter’s probes are touching a small USB breakout board connected to a braided USB cable, which is plugged into a laptop on the right.

And I did confirm, going from breakout board to breakout board, that the cable is good on all pins. I also tested several USB-C to USB-C cables; all were fine, and none provided the 5v from my laptop (I checked all pins, just figured showing one pic of the testing setup would be enough):

A digital multimeter displays a reading of 0.07 while its probes are connected to two USB-C breakout boards. The boards are linked to a laptop via USB-C cables, suggesting an electronics testing setup to measure voltage or resistance.

So, is there something in the Mac hardware and/or software that prevents sending a 5 V signal and data signals? It doesn’t seem like this should be an issue because I’ve powered microcontrollers that have direct USB-C ports on them via the cables just fine. I’m missing something here, but I’m not sure what.

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