JP1 Remotes

[WagonMaster]

To anyone who's interested in building their own Do-It-Yourself (DIY) JP1.x interface hardware, I have a few recommendations and even a couple of part numbers that you may find useful.

Firstly, let me explain part of the motivation for this post. I suspect that a lot of people building their own interface hardware (and probably even some of the vendors) are using the popular IDC connectors (think of a 2x3, 6-pin version of an old IDE hard drive cable connector from a PC) and flat ribbon cable. While in many cases that will work fine, there are a couple of good reasons not to use that technique.

1. Some remote controls, like my Radio Shack 15-135 (and probably the 15-133 and 15-134) don't have an opening large enough to fit a normal 2x3 IDC connector, forcing one to hack away at either the connector or the remote's opening.
   
   
2. There's the issue (for non-JP1.1 remote control owners) of having to disconnect pin #5 of the remote control's connector to avoid problems with the software inadvertently driving a JP1.2/JP1.3 remote into the undesired 'Background Debug Mode' (BDM) or 'Tool'/I2C mode, respectively. Without taking the somewhat drastic action of breaking the pin off at the remote control's 6-pin JP1.x connector, this is more difficult than it should be if you have an IDC connector.

Therefore, when I built my JP1.x interface hardware, I used a simple connector that fits easily in the tight opening of my RS 15-135 remote. Since the contacts that go with this connector can be relatively easily removed and inserted, disconnecting pin #5 at the remote control end (which is where it must be disconnected to avoid the wire acting like an antenna and causing problems) becomes almost trivial. If you have both a JP1.1 and a JP1.2/JP1.3 remote (not as likely these days, but mentioned for clarity), you could even build this single circuit for all your remotes and enable/disable pin #5 as needed.

I purchased my parts from Mouser (www.mouser.com), but I'm sure Digikey (and probably Newark) have the same connector and contacts.

In case the part numbers change in the future, the parts are called "AMPMODU short point wire-applied connectors and contacts". The connectors are Mouser part #571-104482-2 ($0.89 in Jun 2009). NOTE: The image of the connector is only somewhat representative of the actual part. The connector shown is a 22-position model (2x11). The part number above is for the 6-position (2x3) version, which is obviously the one you want.



The contacts that you need to insert into the connectors are Mouser part #571-1-104480-4 ($0.12 each in Jun 2009). Be sure to buy (at least) 6 contacts! Since you might mess a contact up while first trying to secure one to the wire, buy extra -- you'll thank me later.

NOTE: In the contact image below, the wire is crimped on the left side and the right side goes into the connector. The little piece sticking up on the top right side is the part that clicks and locks the contact into the connector. It also allows one to remove a contact from the connector after it's been inserted -- you merely push down on it to unlock it and pull the wire/contact back out. That can be useful in the rare case where you need to enable/disable JP1 pin #5 for use with JP1.1 and JP1.2/JP1.3 remotes.



While I'm at it, assuming you only have JP1.2 or JP1.3 remotes and not the ancient JP1.1 remote, I'd recommend building the simpler of the 2 interfaces described in Tommy Tyler's design document for JP1.x interfaces. That's the one which uses a 14-pin, quad-XNOR DIP (74HC266, Mouser part #595-SN74HC266N, $0.48 in Jun 2009).

I don't have part numbers for the other parts (e.g. resistors, DB-9 end of the cable, etc), since I used what I had laying around. I used some old 6-conductor phone line that I had, but if you have some old Ethernet 8-conductor Cat-5 cable around, that should work equally well.

After bread-boarding my circuit and making sure it worked, I wire-wrapped it on a simple perf-board (available at any local Radio Shack if you don't have it), tested the circuit again, then soldered the wire-wraps for extra permanence and security.

The connector/contacts I recommended have a rated number (which I cannot seem to find at the moment) of plug/unplug cycles, but I doubt anyone will wear one out in normal JP1 use. And if you do, you followed my advice and you've already got some spare contacts, right?

I hope this advice proves useful to someone out there considering building their own JP1.x interface hardware. It's not that hard to build if you're at all handy. And you don't even have to be good with a soldering iron -- if you can twirl a wire-wrap tool (available at Radio Shack [276-1570A, $6.99 currently] and elsewhere), you can wire this circuit.

Regards,
Bill

EDIT #1: Unbeknown to me, someone (I assume it was Rob -- thanks, Rob!) thoughtfully added a couple of images from Mouser's website to my original post, in order to illustrate the connectors and contacts. I've added a couple of notes to clarify what's illustrated in the images.