Dangerous Prototypes

We've been on a multiyear quest to make a durable, affordable, usable probe cable for the Bus Pirate. The one currently sold by Seeed is inexpensive (good) but not very long lasting or particularly usable (not good). I typically use male:female individual probe wires.

With the Bus Pirate education kit almost sorted, we MUST have a better probe before launch. Ideally it will be something with male ends that stick into a breadboard and labels on each probe.

A few times over the past year we've tried to get a new cable put together with labeled probes, but various barriers and misunderstandings about heat shrink and cable labeling always got in the way. It's beyond time to bite the bullet and make an example to shop around for quotes.

This is a opportunity to buy a new toy: a shrink tube printer. At first I looked at several DYMO RHINO models. They are cheap in the US, but extremely expensive in China. All use special cartridges of shrink tube that run about $30 for 5 feet. To compare - 200meters of shrink tube is about $5 in Huaqiangbei... There's also the risk that none of the sizes of shrink tube cartridges available would be adequate or the right color. I mean, what if we want hot pink labels?

A Taobao dealer selling the BYMO RHINO referred us to a professional heat shrink printer that was only about $100 more expensive. In the end the professional setup was less than $40 more expensive because we bought cheap heat shrink in a bunch of sizes and colors instead of the expensive cartridges used by the RHINO.

We chose the L-Mark LK-320P over other brands because it's exported and very google-able. Some of the other options were more enticing, but seemed less known which could lead to ribbon supply issues later. The "P" version means it has a USB port and connects to a computer, where it's much easier to deal with the Chinese interface (and hack?). We paid about $250 for the Chinese version of the machine. You can find the English export version on Alibaba for $400+. We ordered it from a company in northwestern Shenzhen (Bao'on) in the morning, and it arrived in the evening.

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In the box we got the printer, one label cartridge, one black acetate transfer ribbon (called color tape in Chinese), software, manual, and some cables.

We tested it out with the label cartridge first. Not only is the interface (of this version) in Chinese, it's about the clunkiest thing ever. After some fumbling we spit out a few labels with some confusions about what word too long errors and paragraph settings meant.

Next we removed the labels and stuck in some yellow heat shrink tube picked up yesterday in Huaqiangbei. Did you know most heat tube is already printed? I had never noticed before until I tried to find blank tube. I ended up with something with small printing, today I can pick up a reel we ordered from the factory with no printing.

We printed a few Vpu (voltage pullup probe) labels for the Bus Pirate cable. The tube seemed to wander around and printing was inconsistent. Then we realized the label cartridge has a plastic arm that works as a feeder for the tube, holding it down during printing. It's not clear if this is intentional, and it isn't mentioned in the manual. With the tube threaded through the cartridge things started to work great.

The interface, even if not in Chinese, is wretched. We decided to give the PC connection option a shot. Drivers for the USB to Serial chip (by http://www.winchiphead.com/ (http://www.winchiphead.com/)) failed on Windows 7. Ok. Drag out the wonky Windows XP netbook and everything installs fine.

The printer enumerates as a USB to serial device so it's probably very sniffable and hackable. Open it up, bring out the serial, and use a modern converter chip with updated drivers. That presents a minor issue as the software seems to look for it's specialized drivers (no way to set a serial port manually), but sniffing would be very easy and a simple app to send commands from a CSV spreadsheet could be whipped up in no time... But I digress, none of this gets us closer to a sample Bus Pirate probe cable.

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The software isn't great, but it's way better than the terrible menus and poorly debounced keyboard on the machine itself. Each heat shrink label tube diameter, length, font size, cut type (half, line, none), darkness, repetitions, etc are set in a spreadsheet like interface. It's in Chinese but you only need to recognize a few characters to get the basics, mostly cut type. There's an option to import a spreadsheet of labels, which seems like the easiest option, but as of yet we've found no example of the format needed (and the native file is binary which gives no hints). There's an English version of the 320/330 so the software might be available in English, but the downloads on L-Mark's English website fail.

We were up and printing meters of probe labels in a few minutes with the PC connect software.

And then the acetate transfer ribbon (ink, basically) broke. Just snapped. And we had no spares. Using a little screw driver and the smallest fingers in the room we pried open the ribbon cartridge with minimal damage. We tied the ribbon back together and did what we could to rethread it properly. Amazingly this worked!

One thing we spotted in the cartridge is possibly an RFID chip to either ID the type of ribbon, or worse, to prevent third party replacements. The ribbon isn't "cheap" at ~$6 for 80meters. Other machines are much cheaper. However given that we could open the cassette and repair it with minimal damage, we'll probably just respool it with cheap (and plentiful, and high quality) acetate ribbon that's used all over Huaqiangbei to print fake cell phone battery labels with the Postek G-3106 or C-168 (our model).

Verdict: it works, and we're closer to a probe cable I like. Worth the money? Sure, especially if I bought it 12 months ago and didn't waste so much time with false starts on the cables this past year. I wouldn't buy it from Alibaba for $400, that's for sure, and I would stay away unless you've got some basic Chinese reading skills or a friend who can help translate.

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The end probe with GRND on it looks handy. No more "is that cable white or grey"..

Are you going to sell these loose or are you only going to ship them with the "education" kit?

I'll give away sets if theres interest. The new cables at Seeed will have them, and it will aslo be the cable in the education kit.

Does it allow custom font (i.e. wingdings) or has it some things built in?

Besides the crapiness of the machine it looks a cool addition to your workshop.

since you are looking on things like this, can those be used to label ethernet cables? (big enought to pull over the contact, and shrink enough to sit good?)

[quote author="neslekkim"]since you are looking on things like this, can those be used to label ethernet cables? (big enought to pull over the contact, and shrink enough to sit good?)[/quote]

You have sheet of special adhesives for this. about 75% of the adhesive is transparant and 25% is white. After printing you can wrap them around the cable. A random link to the sheets: http://www.ncusa.com/labeling/main.htm (http://www.ncusa.com/labeling/main.htm)

and that works?, we have tried some brother/dymo but the adhesive loosens and makes an sticky goo on the wires, so I thought something heatshrink based would be nice.

@Neslekkim - Proper trade labels for use with proper industrial printers like Brady, etc. work pretty well. As Sjaak pointed out, they have a clear section as a portion of the label and that wraps over the print to laminate it. It works OK for many applications, but heatshrink or hard plastic labels are better in some applications. Yes they can slip and get messy in some applications, but better than normal commerical stuff like Brother / Dymo.The industrial stuff from Brady, etc. is not cheap though.  You can also use Raychem (and others) type of heatshrink sleeves such as these http://http://australia.rs-online.com/web/p/cable-label-printer-accessories/2672578/ and many of these types can be used with standard old-fashioned Epsom dot-matrix printers when you use a special ribbon. The print becomes permanent when it is heated / shrunk and will resist even diesel, solvents, etc. Lots of different types / prices, so check around the trade suppliers.

[quote author="neslekkim"]and that works?, we have tried some brother/dymo but the adhesive loosens and makes an sticky goo on the wires, so I thought something heatshrink based would be nice.[/quote]

Not had problems with them. removing them gets very messy though ;)

Some ideas:
- If you can open it up and directly sniff out the data lines, you can write you own program for it. You have to try bunch of different settings and match them up with the sniffed signal. Another way can be using the software sniffers in Linux and running an XP virtual machine on top for the program. Not sure if better or possible but something to think about.
- RFID chip: Probably it stores some sort of ID number so that the printer can adjust the settings of the printer. Saw a similar thing on the crappy mobile printer I bought recently. It has a paper cartridge with black squares and couple of light sensors on the machine. According to the manual, it uses the sensors to identify the type of paper and adjust heater elements and other stuff. Anyways, the RFID data can be read, it's probably 125 kHz, then you can program your own RFID stickers and use any cartridge.

Nice to hear from you Ian!

Yes, the later model Brady Industrial printers use RFID on the ribbon rolls, as do other professional print systems, it's mainly to identify the type of ribbon, film, etc. to save you having to manual enter the details - and probably so they can charge more for their own branded stuff. It is possible you may be able to just peel it off and use it over and over with another better/cheaper/etc. cartridge.

Print quality

Print quality seems to depend heavily on the shrink tube. Cheap, highly flexible tubes that compress flat in the printer look beautiful. Expensive, thick tubes range from fair to crap.

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We picked up 20 meters yellow and 20 meters white high quality shrink tubing, 3.2mm diameter, 3:1 shrink ratio on Taobao for $0.20 per meter. Most tube has some kind of marking on it already, but this tube is totally blank. We thought it would be perfect for printing, but it's too stiff and doesn't hit the print head properly. The white tube printed ok, but the yellow tube looks awful.

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Next we grabbed a reel (200 meters) of white and yellow shrink tube from Huaqiangbei for less than $7.00 per reel. This stuff is very thin, flexible, and the prints look great. It already has marking along one side, but if we hold it right it stays on the back of the tube and doesn't interfere with the print. It's a pain, but it's just a prototype.

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From left to right: expensive white, expensive yellow, cheap white, cheap yellow.

Sample cables

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Here's a sample cable in yellow, and one in white. The white one looks cleaner, but the yellow looks a bit cooler.

Additionally, there's two styles of printing - one justified to the left edge of the pin housing, the other centered in the shrink tube. Both cables have half of each. I like the left justified better because the print is much larger and more readable over the crimp housing, however it's also "upside down". I'd prefer right justified but the label printer doesn't have that as an option.

Hopefully for the final cable we can also source an extra long housing that's easier to handle.

I'd really appreciate your feed back on:
1. Yellow or white tubing?
2. Left, right, or center justified printing?

I have a bunch of sample tubes I made while experimenting, and you can have a set in exchange for your opinion :)

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Can't you right justify by sliding it on upside down?

I prefer the left justified.  I find my eyes start at the end of the material anyway, when they encounter nothing the blank space feels confusing.

I guess printing on both sides is out of the question?

Just for reference, this is what Xilinx does.  I guess the real question is when are you looking at the labels?  Mostly during hookup, once they're in place do you read them?

For making instructions photos I guess it is handy to have them at the circuit, but perhaps colour is enough?

I'd also like to see a little more heat-shrink too, longer lengths just feel more robust (provided it is thick enough)


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[quote author="ian"]I'd really appreciate your feed back on:
1. Yellow or white tubing?[/quote]

White, definitely. Also it will be a better platform if you ever start experimenting printing in colour (to match the wire colour?).

2. Left, right, or center justified printing?

Well that depends on whether your cable goes from left to right or right to left on your bench. But since left-justified is easier to realize than right-justified, go for the left.

Also I'm not convinced longer housing is that great an idea. In your pictures the wrap is way too long (I understand it was to print two label styles), and it kind of decouples the pin from the wire colour, which is what becomes important after a few uses and you've memorized what colour is what signal. Since the heat shrink label has to be longer than the housing and overlap the wire, regular sized housing sound good, especially given that the heat shrink itself will become the new handle since it's relatively stiff once shrunk.

I would vote for black on yellow, as this it is the colours of dangerousprototypes. Besides that i find it more appealling to read.

I would say left justified, so the text start on the same position. Or sell also a right justified version for lefthanded people ;)

Just thought I'd add a quick +1 to Sjaak's remarks.  I prefer yellow as it should be easier to find on my cluttered bench.  And now he's pointed out it conforms to DP branding guidelines I can't unsee that.  Left justification should also look neater on the breadboard (text starting nearest the board).  So it's yellow with left justification please.

I can imagine you can't place the pins next to each other on a .1" spacing, due to the tubeshrinking?

Walked the cable around for a quote. NOBODY does heat shrink labels, and the heat shrink place said our printing was better than theirs lol. Seeed's cable girl gave a great tip though - dip the cable in boiling water to shrink it. That looks beautiful!

We'll be doing two batches of cables. A company is making 200 cables without shrink tubes. We also ordered 100 printed shrink tubes from the only place that would do it (and they're expensive!). The cable company will put the 100 tubes on 100 cables for free. The other 100 cables we'll print tubes ourselves and apply them in-house. That should give an idea what the cost of our various options vs quality are. All 200 cables will probably go in the giveaway drawer, but might end up at Seeed too.

[quote author="ian"]Seeed's cable girl gave a great tip though - dip the cable in boiling water to shrink it. That looks beautiful![/quote]

Isn't that going to capture moisture or even liquid water between the cable and the tube? This might leak progressively and be problematic for electronic work, no?

It's pretty open and we'll hang them up to dry in front of a fan for a day. I cut a bunch open we did like this and there was no problem.

Professionally printed shrink tubes arrived for the Bus Pirate probe cable prototype. 110 each of 10 labels cost 180RMB ($30). These about about 5x more expensive than printing them ourselves on the L-Mark (ribbon+tube cost). They are really nice, the print quality is more consistent than ours and the font nicer, but when it's shrunk on the cable there's little difference. I think we can probably print these ourselves and get the cost of the cables a little cheaper.

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I +1 the Yellow, my experience with white out in the field is that it gets dirty very quickly. Yellow isn't far behind, but but is a bit better.  The boiling water idea I don't think is great, liquids can go up inside the wires and also between cable jackets and wires - I've seen it dozens of times. A heat gun works great so long as you don't go nuts, but the hot-air reflow unit works great. If you must use water, then I'd suggest a good dip in IPA afterwards        ...Oh and don't use the water for your cuppa' afterwards ;)

Pity you can't have decently thick wires on it, in Industry on Multicore cables, it's very common to have the numbers and / or various other info printed on the wires themselves and with say 0.5mm[sup:]2[/sup:] or above, it's usually pretty easy to read.

Ian,

I wonder if this is a good time for a customer survey to see what people use their bus pirate(s) for.  eg. I have one that is dedicated to avr programming.  I finally made an adapter cable this week.  Perhaps there is a market for a kit of uP programming cables for the pirate, avr perhaps arm jtag, not sure what else - xilinx?

Tom


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We sent the professionally printed heat shrink tubes to the cable people and they put them on 100 cables. We have another 100 cables without the tubes that we'll apply ourselves.

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The cables look great, and they did a great job applying the professionally printed shrink tubes. The manufacturer complained though that it took 8 hours to apply the labels to 100 cables. Not great, that's just over ten per hour. Yikes.

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We fired up the L-Mark and printed shrink tubes for 100 cables. It is a nightmare job. Each probe wire has to be peeled back, then the tubes applied and aligned before being shrunk. We're doing a bit better than the factory, but not by much. It will probably take 4-5 hours to finish 100 cables.

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I suspect this is why labeled heat shrink isn't more abundant

It would probably be quicker with some form of jig. 'Plug' the ends into the jig plate (or header if female), that way you can push the heatshrink down to the jig plate and not have to worry much about alignment. Then just heatshrink the lot in one go. I imagine that would be a lot quicker than doing them individually. There's still the termination of course, but you see lots of breadboard jumpers on ebay, etc. so they obviously manage to do that part at a profit. With 3:1 heatshrink, it should be fairly easy (albeit fiddly) to slip it over the terminal and then just push it back till it hits the jig plate.

Kit job?

Using the heat shrink does provide a nice end solution however it sounds as if the amount of labor required to assemble these just doesn't really make economic sense. Have you looked into having the ribbon cable inserted directly into a break-apart 1x10 plastic housing that is slightly extended and just silkscreening the labels onto it? It would drastically reduce the assembly costs since the wires do not need to be separated and less chance of an accidental mis-label.  Heck, you might be able to find a shop to produce an inexpensive mold that has the labels embossed right into the ends... maybe even nice round ends with simple strain reliefs. I would gladly pay $10-15 for a cable set if it would last and was made of good material.

I understand these are for the BP kit and so you want them male for bread-boarding, but myself I generally prefer female terminals, so that I can hook them onto XKM e-z hooks and the like.

Got my cable from the giveaway today. They surely look nice - thanks to DP!

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The labels feel rather stiff, this makes the pins much easier to hanel in my opinion (better grip on them). Unfortunately I didn't remember that I have the Sparkfun version of the BP - so the header is reversed and none of the label match :( SO I will try to carefully open the connector and reverse the cable.
The pins itself look cheap, OTOH. They look like the got just cutted out of a large sheet of metal:

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(Compare with normal header pins as reference) I'm not sure how much of a problem that is, but it surely looks strange.

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Someone else is doing this, check out the labels on this cloned xilinx cable....

http://www.ebay.com/itm/Xilinx-Platform ... 0809652326 (http://www.ebay.com/itm/Xilinx-Platform-USB-Download-Cable-Jtag-Programmer-for-FPGA-CPLD-C-Mod-XC2C64A-/390809652326)


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I think those are cable labels and not heat shrink. The L-Mark can print both. I was really hung up on the heat shrink, but should really check out the labels too.

So thanks to the Free PCB coupon program I got a set of white labels. The sure look nice too even without the cable:
[attachment=1]
(Ok, one of the "3.3V" prints looks wrong, but apart from that its really nice)
My plan was to use them on my other two Buspirate probe cables. I have one with IC hooks attached and a Sparkfun cable (with female headers). It turns out that it doesn't work:
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I don't think the labels will shrink that much, so I'm stuck. No "free label build" this time :(

Any ideas? I might use real headers instead. Or trying to stuck something inbetween the cable and the label. That might also work with the IC hook cable then.

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A little bit of hot-melt glue should do fine. Put a little on the female header (keep it away from the connection end) and then pull the label over it. Then rotate it a bit to get the glue all around. Alternatively, you could use smaller heatshrink to build up a layer or two, then shrink the label over that.

Thanks for that tip - it worked like a charm:
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I did place a small string (about 5 to 10 mm) of glue right where header and wire meet, then just pushed the label over it. No need to rotate or fill out the label, it just needs to stick. When the glue cooled down, I used the hot air station (set to 180°C) to shrink the labels. While doing so the glue starts to melt again slightly, and due to the shrinking label it nicely fills out the inside.

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Glad to see it worked for you. Just as a side note, hotmelt glue can corrode some types of (bare) wiring. This shouldn't be any issue in your application, but I did find this when repairing some tinned wiring on a laptop power supply cable where the glue was in direct contact with the tinned wiring.