Connector J3 is a polarized shrouded, right-angle header. There is a molded triangle intended to identify pin 1. However as used in this reference board -05, the pins of that connector are numbered such that the arrow is on the pin 19/20 row. If you use a ribbon cable and 20-contact IDC receptacle to mate with J3, it's going to cause confusion. Fortunately the board silkscreen has the correct pin numbers. To support those numbers a ribbon cable with a pin 1 stripe is going to have to be made deliberately wrong: with it's pin 1 not matching with the pin 1 triangle on the header.
What can be done about this now? I don't know if versions of a header are available with the triangle on the other end of the connector. It's possible that the pins were numbered incorrectly, without regard to the polarization markings.
It's also odd that the ref board ships with a receptacle cable which is too small for the board shell and is non-polarized, creating the likelihood that someone will plug it in the wrong way and end up damaging the board (the very thing a polarized shell should prevent).
I'll research this more asap when I have ribbon cable parts on hand.
Connector J3 is a polarized shrouded, right-angle header. There is a molded triangle intended to identify pin 1. However as used in this reference board -05, the pins of that connector are numbered such that the arrow is on the pin 19/20 row. If you use a ribbon cable and 20-contact IDC receptacle to mate with J3, it's going to cause confusion. Fortunately the board silkscreen has the correct pin numbers. To support those numbers a ribbon cable with a pin 1 stripe is going to have to be made deliberately wrong: with it's pin 1 not matching with the pin 1 triangle on the header.
What can be done about this now? I don't know if versions of a header are available with the triangle on the other end of the connector. It's possible that the pins were numbered incorrectly, without regard to the polarization markings.
It's also odd that the ref board ships with a receptacle cable which is too small for the board shell and is non-polarized, creating the likelihood that someone will plug it in the wrong way and end up damaging the board (the very thing a polarized shell should prevent).
I'll research this more asap when I have ribbon cable parts on hand.