Is there a standard way to number lines on a FFC (Flexible Flat Cable)? In other words, if you see the FFC end from the side with exposed contacts, do you usually start counting from the left or from the right?

  • \$\begingroup\$ Which end is left? \$\endgroup\$
    – Andy aka
    Mar 28 '15 at 11:49

A common solution for determining cable wire numbering is to look at the connector that it is mating with see if the connector manufacturer has assigned a pin 1 to the connector. That works fine in most cases but can fall flat when beginning to use FFC that is a simple straight end to end cable.

As you can see in the image below if you define pin one at the arrow on one end of the cable then the cable routing demands that pin 1 be at the location of the other red arrow at the opposite end. So for your cable one end from the left and the other end it is from the right!!

enter image description here

(image borrowed from here)

So this becomes a careful job of systems engineering to correctly comprehend the signal routing when FFC cabling is in use.

  • \$\begingroup\$ Yes, you are right. I completely failed at noticing this. Sorry for the stupid question. \$\endgroup\$ Mar 28 '15 at 13:01
  • \$\begingroup\$ @giomasce - It is not a stupid question at all. You would be amazed at how many times in this industry that board designers have copied the connector pinning schematic from one board (similar to above) and pasted the exact same pinning into the second board schematic. Without comprehending this correctly they have to re-spin their boards. In some cases they get lucky and have used FFC connectors that support both top and bottom contacts. In such case prototype boards can still be used for testing if you put a 180 degree twist into the FFC cable. \$\endgroup\$ Mar 28 '15 at 13:11

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