Friday, March 27, 2015

New driver board installed in SAC Interface box, wiring almost complete


I visited Anchor and returned with the parts to build my new driver board. I set up the work table outside the opened garage and went to work. I worked at a decent but careful pace, ending with seven hex inverter chips, their power condition capacitors, 41 pull up/termination resistors, headers for the 41 input and 41 output signals, plus the power supply connector in place. This took me until late afternoon.

New driver board, during wiring into the SAC Interface
It was then time to carefully remove all the driven signal wires from the four interface boards which are now exclusively receiver circuits. These were being extended and connected to the new driver board, along with the wires to the FPGA board. To extend the twisted pair signals coming from the 160 pin connector, I used some twisted pair ribbon cable I recently bought, which is normally fastened to IDC connectors but I separated the leads at both ends.  I individually connected the leads to my new board and to the twisted pairs from coming the big connector.

Twisted pair ribbon cable used to connect driver board to 160 pin connector signals
By the end of the day, I had the entire set of circuits from the first board - 12 signals - wired up to the new driver board and their associated lines going to the FPGA board. Further, I had removed all twelve of the 1131 side signals from the second board, labeled them, but had not begun wiring them to the new board.

After dark, I brought in the rest of the ribbon cable stock and finished separating the leads and preparing them to make the actual wiring go much faster tomorrow.  I then moved all the fpga-side wires off of the receiver board 2, hooking them to the new driver board. The new ribbon cable was hooked to the 1131 side lines I had previously removed.

Ribbon cables prepared for wiring up circuits from boards 3 and 4
I have one more full old style interface board that has driver circuits to relocate to the new board, twelve more 1131-side signals and their fpga-side analogs. The final old style interface board is used to implement five driver circuits, thus when they are relocated to the new driver board, that fourth interface board will be removed entirely.

After this modification, the box will still have four boards for interfacing between 1131 and fpga, but three are used for the 36 incoming signals and the new board handling all 41 outgoing signals will be the fourth. The extension of the outgoing signal twisted pairs over the twisted pair ribbon cables will give me more room to mount everything in the box, also facilitating debugging and maintenance as needed. 

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