TOPIC:

Hi all. I'm not a noob to car stereo but this is my first time doing everything from scratch. My intended setup is a raspberry pi running Open Auto Pro sending SPDIF to the CDSP 6x8 which then sends out to the amp. I'm stuck on the CDSP powering on, though. I can't tell if anything's happening. I  have constant 12v into the appropriate spot as well as the ground. I am using the remote wire feature so I have that hooked up (and the jumper is changed) and that will send power out to the raspberry pi (and a display) running off a small USB power bank.

The catch is that I can't tell if the CDSP is powering on at all. The remote wire goes from 0v to 12v when I turn the key: all good there. The ground constantly is 0v (and an ohm meter test shows 0 ohm when I connect the other end of the multimeter to the chassis so the ground is nicely grounded.) The constant power has me stumped. When I do not have the CDSP plugged in, that wire is a solid 11.8v the whole time – and I figure that's close enough to 12v, it's what powered the factory head unit – but when I plug in the CDSP, measuring volts at the CDSP's power terminal block on the little screw on top only shows 4v.

Now it's entirely possible that I am misunderstanding car audio wiring here and this odd 4v reading is what I should be seeing when the CDSP is drawing power, but the CDSP's remote doesn't light up at this time, nor does the CDSP remote power out send 12v (regardless of how the jumper is set).

Any ideas? I'm stumped. Thanks!

Can you sketch out a simple power side wiring diagram ?

From paragraph 1, it seems like you are using the REM out wire of the CDSP; to supply power to a powerbank (which powers a display + rasp pi). 

Re: paragraph 2, can you isolate and power the CDSP externally (12V wall wart or other means) and verify it is still working (LED, USB connection) ?

@danthe0 is correct. A diagram will go a long way as the CDSP 6x8 is most likely not powering because it's not receiving +12V from the REMOTE IN? 
Just a wild guess.. Use a DC multimeter to double confirm it? 

Devteam