Saturday, September 26, 2015

Using fiber optic camera to work on 1053, plus continued SAC Interface enhancement work


The fiber optic camera arrived today - may be a problem getting all the way into the small spots as it has an 8mm diameter (just under 1/3" for the metrically challenged). It also focuses 1" from the lens, which is a huge distance compared to my problem area, but we will probably get a better idea of what is going on inside, even if not perfect.

Fiber optic camera - inexpensive but quite useful
Looking with the camera in one of the few spaces it can fit, I did confirm that the problem is the rearward pulling spring that hooks to a bar at the back of the typewriter frame and with its front over a hook shape on the tab interposer. The spring is not hooked to the interposer.

So far, the camera does not give me a view of the critical area - the hook shape on the interposer and the far end of the spring - which is what I need to attempt a reconnection. I found a few other angles where I can insert the camera.


I worked further on the PC side code, to allow the reader files to be opened, a 'blank deck' file to be created for punching, and to have the system convert between the 1130 word format and the file format. Before I can fire up this version of the SAC Interface Box, I need to have either:
  1. The logic for the virtual 1442 disabled so that it doesn't react to the area code for the device                                                            OR
  2. The device adapter circuits in the 1131 disabled by tying the area code 2 signal to ground
Ideally I can set up a logical switch, set by the PC program, such that the SAC Box ignores area code 2 unless I have set the DSW to ready. I will work on that circuitry in the fpga next.


I think I might change from the current medium speed link - an SPI protocol to link to Arduino controllers - and instead make use of a shared I2C bus to several IO concentrator boards. These boards control 16 IO pins (plus more) and can be strung together on the 400KHz I2C bus to handle all the slow speed signals for devices like the 1134/1055 paper tape units, the 1627 plotter and so forth.

I have ordered some boards which I should have in a week, so I need some design work to take advantage of these. I can always hang Arduinos or similar microcontrollers to deal with transient signals and other timing that might be too slow for the I2C link delays.  The board I bought.
I2C 16 pin IO breakout board

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