Main Site Documentation

IDC Cable Lenghts


#1

Hi Guys
Whats the maximum usable length for the IDC cables? I see that they are available up to 50cm but can they go much longer?

Cheer Hughb


#2

There will be some maximum practical limit. For parallel signals increased cable length causes an increase in the differential in time in which each signal takes to traverse the cable. This can cause the device receiving the data to try and latch the data bus before all signals are valid. There will be similar limits for something like the USB module as the signal will degrade. For simple I/O timing will not be as critical but longer cables stand a greater chance of picking up electrical noise from the environment.

If you have a specific use case in mind it might be easier to give more specific advise.


#3

Hi Jeff
Many thanks for the fast reply. I was thinking of using the extender module as a kind of edge device type connector. The best example would be something like an RFID reader and lock actuator where the extender module is located close to the lock and reader and the Spider mainboard located elsewhere with say upto 10 meters of cable between the two. I guess an alternative would be to have a Fez Mini and a Xbee at the remote end?


#4

The question is what will the cable do, not what does the module do.

Example, you have a module that needs serial data at low baud rate like 1200? Then make the cable as long as you can. Maybe a cable with on/off signal? Then make it as long as you like.

On the other hand, a module like display may need 30Mhz or more on the wires and so, make the cable as SHORT as you can.


#5

Many thanks for the update Gus. I think the serial method will work nicely.
Really looking forward to the future of the spider and the projects that people come up with.

Cheers all
Hughb