footprint mistake m / f header - Page 1
Forum section: electronics / projects

author: djacobow
author_rank: Super Contributor
timestamp: August 06, 2022, 09:40:59 pm
content: I used a female head footprint on my PCB when I should have used the male footprint. (The IDC cable I want to use is f/f and the other board is male.) As a result, the even/odd pins are mirrored.Is there an easy fix for this other than spinning the board? I'm thinking of some kind of cable orientation shenanigans.As a one-off, I solder the header on shifted so that the top connector pins were on the bottom pad row, then used wires to connect the bottom connector pins to the top pad row. It worked, but yich, I don't want to do it again.

author: DavidAlfa
author_rank: Super Contributor
timestamp: August 06, 2022, 11:24:48 pm
content: So it's mirrored, not rotated?The only solution I can think of is to try to find a pcb to pcb female connector and make a small board for it, like a sandwich.Can't you just use the female connector and change the cable type?

author: djacobow
author_rank: Super Contributor
timestamp: August 06, 2022, 11:48:48 pm
content: Maybe I can just use a female connector and use a male/female cable as you suggest. I have a hard time visualizing this. Am I the only one who does?

author: exmadscientist
author_rank: Frequent Contributor
timestamp: August 07, 2022, 10:13:48 am
content: Quote from: djacobow on August 06, 2022, 11:48:48 pmNope! Ribbon cable orientation stuff is one of the worst parts of this job. I usually have to whiteboard something three times before I get it right (or even stand a chance)... and that's when there are only two possibilities!From the it-could-be-worse department: we once had a ribbon cable row pitch issue (thanks TI). My colleague produced this horrid three-chained-custom-adapter-cable monstrosity that managed to successfully get Tab A into Slot B. I... just crimped the right connector onto the cable that was supposed to make the connection (losing about a half inch of cable length and still leaving the original connector usable if wanted). The anxiety over whether I'd actually gotten the orientation right, or whether this solution was even possible, was very palpable, along with the dread of certain humiliation should I be hoist on my own petard. Fortunately, I flip-flopped on my answer the right number of times and it just worked! Every subsequent cable was then produced in the usual Gold Standard way:make it exactly like that one!I hate ribbon cables.

author: Ian.M
author_rank: Super Contributor
timestamp: August 07, 2022, 10:42:55 am
content: No matter which way you fit the female connectors to the cable (without much splitting and twisting), pin 1 (or the max. pin no. if you reverse it) will always connect to the first wire of the ribbon. You'll never get pin 2 to connect to the first wire.However if you mate two female connectors with a long pin header in-between to join them, or fit a through hole header from the opposite side of the PCB, it swaps pins odd-even (1-2, 2-3 , 3-4 etc.) because from the underside of the header footprint its mirror imaged.Lastly if you split the ribbon cable after every second wire, and twist each pair 180 deg, then somehow hold all the split twisted pairs in place and fit the connector you'll get the odd-even swap you need.You don't appear to have room under the board to put the header on the underside, so your options are limited to fitting a female header and using a male IDC connector, or using a short second F-F cable + a long pin header as a odd-even reverser, or building the mega-hacked twisted cable I just described.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: August 07, 2022, 07:43:30 pm
content: What Ian suggested in his second paragraph will be easiest.Cut the ribbon cable, crimp on a female plug on each end and plug them together with a male header that's long enough to make good contact with both plugs.This will undo the mirroring.No soldering required.

author: djacobow
author_rank: Super Contributor
timestamp: August 08, 2022, 03:49:15 pm
content: Thanks. I'll order the male header to try this