How-to: Bus Pirate probe cable

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Update, Saturday July 4th, 2009: All preorders are closed.

A probe cable makes it easy to connect the Bus Pirate to a circuit and get hacking. Good test clips make quick connections on cramped PCBs without causing short circuits. We made two cables for the Bus Pirate v2, keep reading for an overview of our designs and list of part suppliers.

Friday, July 3, 2009 is the last day to pre-order a Bus Pirate. There’s only two days left to get your own Bus Pirate, fully assembled and shipped worldwide, for only $30.

Overview

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We use these cables to connect the Bus Pirate’s I/O pins to a microchip or test circuit. A cable consists of a 2×5 connector, a cable, and some kind of attachable probe like an alligator clip or test hook.

The gray cable (top) is a ‘junk box’ cable, we recycled it from scrap parts and old computer hardware. The ‘expensive’ cable (bottom) uses high quality and special-order parts.

2x5pin female connector

The Bus Pirate’s I/O header is two rows of five 0.1″ spaced pins. We used a 2×5 arrangement because 2x5pin female ribbon cable connectors are common and cheap. We decided against a single row of 10 pins because the connector is an expensive specialty item.

The pin names are shown above, and are silk-screened on the bottom of the PCB. See the Bus Pirate page for detailed descriptions of each pin function.

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The junk box cable uses a 2x5pin female connector from an old PC ISA card.

The expensive cable uses a black connector with a reinforced cable holder. Mouser has gray connectors ($0.69) and black connectors ($1.15).

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Ribbon cable connectors have internal pins that pierce the cable when the top part is pressed onto the bottom part.

Ribbon cable

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Standard 2x5pin female connectors attach to 0.05″ 10-strand ribbon cable. The wire thickness is usually 22, 24, or 26 AWG. We think 12inches (30cm) is a useful length that doesn’t get in the way.

Grey ribbon cable is pretty common. We salvaged a piece from an old computer connector, you might get lucky and find one with a 2×5 connector already attached.

A color coded cable makes it easy to identify each connection. DigiKey has 5 foot sections ($3.03), Mouser has it by the foot ($1.16, $1.19).

Ribbon cable is cheap and readily available, but it tends to tangle and kink. A really nice probe could use a ribbon cable stub attached to thicker test leads.

Test clips

Test clips are the most important part of the cable. They have to be easy to position, and maintain contact with the circuit. Alligator clips work, but there’s a lot of exposed metal that can create short circuits. Professional test clips have a grabber that retracts into the probe leaving less metal exposed.

Alligator clips

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The junk box cable has alligator clip probes, we pulled them off test leads like these (40 leads for $12). You could also use loose red and black clips (20 for $2.30).

Remember to put the rubber housing on the cable before soldering the wire to the alligator clip, it won’t go on later. In the photos you can see that some of our covers are cut to fit over the front of the clip because we forgot.

Round test hooks

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This is the classic, round-bodied test hook. These are great for grabbing onto 0.1″ pin headers, wires, and the leads of through-hole components. The hooks are usually too big to use with surface mount components, and the round body makes it hard to fit more than a few in a small space.

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Test hooks are easy to position. Squeeze the probe to extend a single metal hook, grab something, then release. The hook retracts into the body of the probe, securing it in place and preventing short circuits.

rndhook-apart

Most hooks come apart by pulling the top away from the body. Put the test lead through the hole in the cap and solder it to the metal tab. Push the halves together when the joint is cool.

DigiKey ($17.26) and Fry’s ($14.95) have multi-colored hooks in sets of 10. Deal Extreme has dirt-cheap 10 packs of yellow ($2.30)  and black ($2.33) hooks, but the reviews say the quality matches the price so buy extra (via [haku]).

Flat test tweezers

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Tweezer-probes are great for clipping onto the legs of through-hole, surface mount, and many smaller chips. They usually have a flat body so they fit better in tight spaces than round hook probes.

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This type of probe has tiny tweezers instead of a hook. Accidental short circuits are rare because there’s so little exposed metal when the tweezers retract.

hook-apart

Most tweezer-probes pull apart and have a metal solder tab inside. Run a cable strand through the hole in the cap, solder it to the metal tab, and then press the halves back together.

Tweezer quality varies dramatically among brands, we’ve used no-name probes that bend easily or don’t grip well. The X- series micro-hooks from E-Z-Hook are the Cadillac of tweezer-probes, we first used the XKM version that comes with the Saleae Logic. They’re intended to fit specialty test leads, but it’s easy to solder a wire to them instead. About $2 each, available directly from the E-Z-Hook website.

Conclusion

We highly recommend a cable with hook or tweezer-probes for secure connections without causing shorts. The right probe depends on the parts you use. Round test hooks work best with through-hole parts and wires. Flat test tweezers attach well to small, surface mount chips.

Please share any additional part sources in the comments. We did our best to provide a variety of sources, but there’s going to be some great places we’ve missed.

Friday, July 3, 2009 is the last day to pre-order a Bus Pirate. There’s only two days left to get your own Bus Pirate, fully assembled and shipped worldwide, for only $30.

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Comments

  1. Nick says:

    Excellent info. I’ll have to make a set of each for my Bus Pirate. whenever it arrives.

  2. so psyched

  3. Stu says:

    I already found a supplier of these in the UK, ready for when my BusPirate arrives :-)
    We have a sort of high street electronics enthusiast shop called Maplins, does them at 99p a piece for the sub-mini clips, pretty expensive, but worth it I think.

    http://www.maplin.co.uk/Module.aspx?ModuleNo=5660

    Or you can get pre-built test cables with croc-clips on the other end, a fiver for a black and a red test lead (two).

    http://www.maplin.co.uk/Module.aspx?ModuleNo=5667

    Yes we live in Britain and are regularly ripped off! We’re used to it. I just hope they’re at least the high quality clips.
    You can pay 29p for a single red LED if you shop here! Should be less than a tenth that price.
    Couldn’t find any of those cool tweezer ones though.

  4. James says:

    I have also had good luck with Pomona Grabber clips for SMT use.

  5. az1324 says:

    I really like the ez-hook xkm with square pin connection

  6. cde says:

    The DX Yellow clips have gone up in price. 2.97 for a 10 pack.

  7. mas says:

    I’ve always preferred the Pomona Grabber series

    http://www.pomonaelectronics.com/index.php?i=prodmain&getDetails=1&parent=GRABCLIP

    I find them much more robust (and more expensive, but you get what you pay for) than the EZ-Hooks. For the ultimate in side-side density (fine lead pitch) I use the 635x series. They are delicate, but the best for TQFP probing. In general I prefer probes that have 0.025″ pins – you can pull the testlead off the clip and stick the lead on a header pin. That’s also the fly-in-the-ointment – getting from a 10 pin header/IDC cable to nice 0.025″ sockets on flying leads. My best results came from canabilizing leads I found at electronics swap meets.

  8. spyguy99 says:

    It would be cool if someone could buy a bulk order then resell them to us for cheaper.

  9. Ian Lesnet says:

    The HD44780 LCD adapter for the Bus Pirate works with the LCD library in firmware v0h-nightly. It uses a PFC8574 I2C expander chip because the Bus Pirate doesn’t have enough pins to directly interface an LCD.

  10. Mephistopheles says:

    @mas – those pomona clips look nice, but $502 for a set of 10… ouch.

    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=6351-ND

    I think I’ll do my prototyping on SSOP to DIP adapter boards and stick to my XKM grabbers :)

  11. justin says:

    @stu – craplins price for the sub-mini clips is actually pretty competetive. rs components do them for 98p + VAT + delivery. Farnell – similar price.

  12. justin says:
  13. Ian Lesnet says:

    @UK people – I’m also in the EU, so I noted that Deal Extreme prices include worldwide shipping.

  14. Stu says:

    @justin
    Thanks for the info, I hadn’t considered Rapid Online, I didnt actually think they operated in the uk for some reason until you provided those links!
    wow, 20p a clip in individuals is pretty good! kind of shows maplins 99p as a bit of a rip-off.

  15. noname says:

    It would be quite interesting if somebody would source all the parts and make some kits (either assembled or do-it-yourself kind), of course with worldwide shipping.

  16. TheFallen says:

    The best supplier in the UK is Farnell.

    http://www.uk.farnell.com

    FREE next day delivery :D:D

  17. Vandrid says:

    since you were closed the pre order of bus pirate, so how I could have it one for my own ?

  18. Vandrid says:

    since you were closed the pre order of bus pirate, so how I could have it one unit new prototype for my own ?, Recommendation are gratitude.

  19. Xeracy says:

    MY BUSPIRATE V2 JUST ARRIVED! YAY

  20. picked one up the other day, awesome!

  21. Noob says:

    Guys, im a noob, can someone point me in the right direction to getting started with stuff like this. I dont have a dad to teach me anything.

  22. www says:

    Could anyone confirm that e-z hook from the link is the same as hook above

    http://catalog.e-z-hook.com/item/micro-hooks/e-z-micro-hooks-double-hook-style/xkm?&seo=110

  23. www says:
  24. Mike says:

    Ian, would you email me please? You may be the person to help me with a proprietary serial async protocol that I need to figure out how to match up to a HAM radio coupler. Thanks

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