Thank you for posting the links to the recently released Udoo V8 schematic diagrams and V8 User Manual, and thanks to the Udoo engineers who finally got around to making this information available. I concur with your interpretation of the V8 power connector wiring. The information on page 18 of the V8 User Manual in section 2.2 Electrical Specifications is a little ambiguous; it states: "voltage can be supplied through a DC power jack (CN5) type Singatron p/n 2DC3122-007111F. Internal pin is VIN power line" This is poorly worded, as the internal pin located centrally in the jack (marked terminal 5) appears on the schematic to be unused, and the schematic appears to indicate instead, that the inner sleeve, not the centeral pin, of the power jack (marked terminals 1 and 2) is the positive VIN power line". (The power jack images shown on the right side of the manual page fail to provide any useful information at all.) The ambiguity stems from the symbol used on the Udoo V8 schematics and the Singatron 2DC3122-007111F power jack used on the V8 board. The "V" shaped spring contact shown in the symbol (marked terminals 1 and 2) would be more correct IMHO if it pointed upward or something, as it contacts the inner diameter of the barrel jack, not its outer shell. Clearly, the outer contact of the barrel jack (marked terminals 3 and 4) is the negative VIN power line terminal. I have been unsuccessful in locating data sheets for the specific power jack and plug parts specified in the V8 User Manual as DC power jack (CN5) Singatron p/n 2DC3122-007111F Mating DC plug Singatron p/n 45P06CV230-1A00-01 , but this 2DC1003-000211F datasheet appears similar. Here is how the jack is represented on that page: So, it appears that the ambiguity may have originated with the Singatron drawing. Given that there are at least three language translations involved (Chinese, Italian, and English), it's easy to see how such ambiguity and resulting confusion can creep into technical documents.