Be Cautious... Very Cautious...

When interfacing my evaluation e-paper modules to the STK3700 I had to be very aware of what's going on.

Here is a picture of the e-paper module's interface connector (box header).

Can you spot anything wrong with it?

web connector gotcha.png

At first glance everything looks fine but it's not.

A hint - Have a look where the Pin 1 indicator is on the box header and where it is on the PCB.

 

Pin 1 of the connector is the bottom left hand corner pad

Pin 1 of the PCB is the top right hand corner pad that is square in shape.

 

In other words, a top keyed right angled box header side has been used instead of a vertical box header.

Another mix up with orientation with box headers is when they are mounted on the opposite side of the PCB and if you're not careful end up in a real pickle.

 

This was a common problem with IBM PC floppy disk controllers and cables.

The makeshift solution was to cut and grind the unwanted key of the connector cable to enable it to be plugged in to match the wiring.

(Some box headers had enough flex to have the key forced in without the need to remove the key).

Another orientation protection method used was the use small rubber bungs and missing connector pins to be used as additional keys so they could not be connected the wrong way around.

 

It's not the first or last time you will encounter something like this and it's a really easy way to ruin something.

As a general rule when laying out PCBs make sure that Pin 1 is on the left hand bottom corner with the connector edge at the top because this will ensure that a top keyed right angled box header can be used.

 

http://katalog.we-online.de/em/datasheet/6120xx21721.pdf