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Engineering: the art of making what you want from things you can get.

Yaca: cabling

September 07, 2010

Yaca, as the name suggests, is (currently, because 2 RFM12 modules were built in today) based on CAN, which needs an electrical bus topology. Cabling a house in bus topology isn't that easy, though. To make cabling easier and to make "branch lines" possible, the following pin/wire configuration has been chosen for the CAT5 cable used:

pincolorsignal
1brownCANH
2brown/whiteCANL
3greenCANH (back)
4green/whiteCANL (back)
5orange+VBUS
6orange/white-VBUS
7blue+5V
8blue/white5V GND
9shield wire5V GND
(distribution side)

VBUS, the bus supply voltage, is currently 20 V, but is planned to be raised to 40 V to reduce cable losses (a wire in 100 m CAT5 has 9 Ohms resistance). 40 V is the very maximum that can be used with the TS2576 switching voltage converters used at many places.

Current list of switching converters:

The current bus connector is a common 2x5 pin header with 2,54 mm grid. The female connector is easy to crimp, the male part is easy to solder and both are easy to obtain and widely used.

On the green wire pair (pins 3+4), the bus comes back from wherever the cable went in the first place (branch line). This is the current bus cabling topology (values in brackets are the cable length marked on the cable, the cable distance between two places is the difference, the bus distance on branch lines is double the cable distance):

ControlPanel connector

In the back of the Pocket PC, the connection diagram is as follows (counting starts from the direction of the card slots):

pincolorsignal
1orange/white-VBUS
2orange+VBUS
3brownCANH
4brown/whiteCANL
5green/whiteCANL (back)
6greenCANH (back)

Last modified: February 24, 2011

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