Conventions for general cabling will be based on the following:
Headers are the sockets that attach to the PCB. Pin spacing is 0.1” X 0.1”
Connectors are the sockets that attach to the cable ends.
The preferred cable is twisted pair rather than flat ribbon. The wire pitch is half of the connector pin pitch and therefore is 0.05”.
Cables will be fitted with female connectors. The color-coding convention is == Dark Br pin 1 == (may not always be implemented be careful). The end wire is connected by the connectors to pin 1. The orientation of the cable through the connector either from the right or the left is irrelevant).
Standard for our project cable color:
Dark Brown=pin 1
Red =Pin 3
Light Brown=pin 4
The polarizing plugs that are commonly found on the cables are the central key and the two corner indentations. All of the polarization details are found on the same side as pin 1. Delta (Δ) labels pin 1.
The header connectors on the boards will match this convention as verified with a standard Berg connector.
(Notice that the polarized female connector fits into the polarized male so that pin 1 lines up. They are therefore a mirror image.)
The flasher system may be triggered by ecl pulses from the flight simulator, FS. The old flight simulator has male 34 pin connections oriented as shown below. The ecl-TTL/nim translators ecl inputs are oriented 180o as compared to the FS (see below). The ecl-TTL/nim translators seem to ignore the cable polarizing conventions on their front panel header. Therefore to use these the cable cannot have the polarizing nubs. The ecl conventions are True or high is –09. Volts and False or low is about –1.8 V. Triggers will be transmitted on twisted pair with the Q, Qbar on each twisted pair. The critical point is that the ECL Q signal needs to arrive on the cable on the odd number pins.
Terminating plugs will be required for the Driver boxes.
[Header Detail Note: The driver headers have a design error. The headers chosen have a right angle bend. Consider a non-bent header on the board oriented correctly. You then can bend the connector in or out, toward the center of the board or out away from the board. The correct way is to bend the connector out so that the cable is easily attached. Unfortunately the headers have the opposite convention and correct installation will have the headers facing the wrong way. The fix for the problem at this stage will be to add a polarizing slot to the opposite side of the header and taping over the current slot. This causes pin 1 to move diagonally to where pin 18 would be. If we mount the new connector on the top of the PCB board pin 1 is now in the correct orientation. The result is that the conventions described in this note are valid. This is include for completeness if someone needs to inspect the way the headers are mounted to the board.]