Main Site Documentation

Longer Gadgeteer cables


#1

Hi

I need longer (x3) gadgeteer cables… Is there somewhere I can order them, without extending them myself? I don’t want to use the Extender Module…


#2

The cable pack we sell has different sizes. Please check the catalog.


#3

Direct link for what Gus was talking about http://www.ghielectronics.com/catalog/product/310. There is one 50cm long cable one and 3x 20cm long ones.

I know you said you dont want to extend cables, but what about making your own?jdal did and you can see what you would need here http://www.tinyclr.com/forum/topic?id=7265


#4

Look up the samtec samples thread. If you request a sample, they will send you some. Remember though that they talk about their cables in how many pins wide they are, so you want the ones with 5 in their name. They have at least 14-inch cables (ask me how i know :slight_smile: ) Edit: they will send you a PAIR of cables in each length you request; unsure how many they see are reasonable number of lengths to request at once though.


#5

Regarding longer cables, has anyone seen a need for shielded cables or a clamp-on ferrite in their high bandwidth applications?
Ferrites are easy to add but you have to pick the right material based on frequency of interest.
Shielding often works best by grounding (reference to lowest impedance) at only one end. If there is a need, I can dig up some simple illustrations showing various shield grounding schemes. The best examples IMHO are from Henry Ott’s book.


#6

I’ve done quite a bit of testing around cable length, bandwidth, and error rate–using both differential signals and standard 3V3 logic.

Here’s my short-list of best practice recommendations so far:

  1. It’s generally best to keep cables shorter rather than longer. Gadgeteer uses “chassis wiring” IDC cables which are designed for ferrying data around inside computer cases (rather than long-distance open-environment data transfer like RS232 or twisted-pair cables are designed for).
  2. 5cm cables work for most applications up to several Mbps. For faster applications, you may want to convert the signal to twisted-pair and/or shielded cables.
  3. I’ve experienced data corruption with >=10 cm cables in some applications. This is generally not a problem with socket types like R/G/B (display) or Y (GPIO) but for modules which use socket types like K/U (UART) and F (SD), you may have a better experience with shorter cables…especially if you’re in an electrically noisy environment.
  4. Avoid running high-speed data like USB HS on these cables. There is a practical upper limit to the bandwidth available with small-pitch IDC cables.
  5. The final issue to remember with longer cables is that you’ll get some voltage drop based on the length of your cables. For typical Gadgeteer project lengths, measured in centimeters, this isn’t a big deal; but when you get into measures of meters then this can start to affect your power supplies and logic levels.

A potential product idea is a “Gadgeteer Cable Extender” module which would receive an IDC cable as input and would provide an amplified differential twisted-pair output. Used in pairs, that would allow you to place modules at a longer distance from your Gadgeteer-compatible mainboard, for hardware applications which don’t have precise timing requirements. Ferrites, shielding, and “every other conductor as ground” strategies may also provide advantages, as you excellently recommended.

Chris


#7

Good suggestion Chris about the diff driver. I’ve used them (opto-isolating) on many occasions so maybe I’ll put a Gadgeteer one out there as a contribution.
I just ordered my Spider kit today!


#8

There is a thread here somewhere where someone drew one of these up and I thought they were going to make some. Anyone know what happened to that?


#9

Taking into consideration that was said above, the best way at the moment to keep module further from board is to use more Extender Modules and cables? (for example 10 meters)
Or there’s some alternatives?


#10

@ Zaborius - what are you trying to extend to that distance? lots of ways to do it, but best depends upon your specifics.


#11

For example i need to measure moisture in in different parts of garden… Or maybe keep camera further then 1 meter.


#12

@ Zaborius - the moisture module, which requires an A socket, for analog input, should work at 10m, using so a wire like cat 5 and two extender modules. it might be a little noisy, but with a little software filtering it should work. also depends upon dynamic range of sensor. if range is very small might have problems.

you would not be able to extend a camera which used a H socket. a camera which uses a U socket might work, but again noise and the distance might be too much.

best way to tell is experimentation.


#13

Oh! Great! Thanks, Mike.