Sunday, December 28, 2014

Finding and fixing minor bugs in keypunch interface, problems crop up with SAC Interface


I kept returning to the printer to search for the lost spring, but as of the end of the day I still haven't located it. As a backup, I crawled around on the floor extensively plus searched deep inside the 1130 just in case the spring took an odd hop outside of the typewriter mechanism.

The typewriter will sometimes fail to reset after a carrier return, attempting two or three before resetting the latch. I suspect that the lost spring is somewhere in the string of parts, levers and clutches that handle the CR, interfering with its proper operation, but even with that suspicion it is extremely hard to find.


I completed the detailed test plan last night and set out to work through it step by step today. I discovered a parsing error which I corrected before resuming the testing early in the afternoon.
Progress was steady as I worked through my plan, identified and corrected problems, then restarted any steps where my changes could have an effect.

As the daylight faded, I closed up the garage, took a breather from live testing on the keypunch in order to correct a few anomalies I discovered and improve one area of the code that I don't like.
I will also put together a quickie Python program that will use the keypunch interface to read a deck of cards into a hollerith format or an ascii file.

I will use that to read in some small decks that I want to transfer to other enthusiasts. Once my stacker, release and autofeed are working more reliably I can attack some larger decks but currently I will be hand feeding and nursing the cards through the keypunch.


Everything was ready for the next round of testing. When I removed the 160 pin connector to check the wiring to my interface boards, I discovered that a couple of female pins had been pushed into the socket openings, thus not making contact with the male pin on the cable. One of them was for B register bit 1, one of the signals that had been missing. I pushed them forward into place but given the high force used to seat the cable onto the socket, I have to hope that these are not pushed out of place again.

I found that even with a fresh day and load, I am unable to successfully read and write to the registers using the USB link. I don't know what is wrong yet. I rebooted my PC in case the drivers on the PC side or in the SDK had fouled up, but I suspect it is a more fundamental wedged state of the USB link. I have to understand the condition and build in a means of clearing it as part of the startup of my PC side program.

When I loaded the new logic configuration to the flash and brought up the 1130 with the SAC box, nothing worked. I didn't see any signals and my interrupt request wasn't detected. I leaned over to look at the back of the 160 pin socket and could immediately see several female pins pushed out of contact. Although every signal on the cable is a twisted pair, IBM didn't connect the ground wire on both sides of every signal. Instead, just one pin is used to link grounds.. If that pin is pushed back like several of the others, it would cause exactly this symptom.

My first task is to get all those pins back into position contacting the male pins of the cable. Given the thicket of wires emerging from the back of the 160 pin socket and limited maneuvering room as the box is assembled, this will take a bit of time. I didn't finish this by the end of the day today.

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