/diy/ - Do It Yourself

>>1634431
>what happens when the parallel-load pin goes high just as a key switch is making in the other state
With the resistors involved, I don't think the voltages on the other buttons would dive to Vcc, but you might be right, I'd have to draw it as a diagram and see.
>async
No I didn't mean asynchronous, just that I'd have a small delay in the keyboard circuitry itself to offset an extra clock pulse to clock the shift register with the parallel-load enabled. The 165 IC itself has the function that the CLK input is used both for L-shift and for parallel-load, depending on the state of a third pin, meaning the CLK needs an extra pulse in there aside from the regular refreshes. Kinda wish it didn't to be honest. Pic related.
I'll probably just feed the data into a raspberry pi with the pi itself outputting CLK and LOAD for testing, no MCU required. From there I'll see if either my software can be simplified to fit on an MCU or somehow build a desktop application via USB or something, which might require some more complicated synchronicity or lack thereof. And get that godawful RS232's ±12V out of my face.
>are those the actual switches
That was a SPDT toggle I had lying about. Since a momentary switch will have unidirectional springiness / the lever doesn't have to move past an area with no torque, I imagine this timeframe will be smaller with the microswitch. Might buy a similar microswitch for a few dollars from the local scumbags to test.
>I wouldn't worry if it were my test rig
What, so go with no current limiting? I'll bust out one of my 74HC04s so I can run the capacitor experiments with CMOS impedances and see what kind of results I get with and without current limiting. Assuming a time constant of 500ns with a capacitance of 1nF, that's a 500Ω resistance, with maximum current of 10mA. Which is easily passable for long-term use.