/diy/ - Do It Yourself

>>1691701
I once played with a surplus keyboard extracted from thumbnail related. it was self-scanning, with the binary output of the key scanner directly connected to its interface header, or maybe there was a tri-state driver, I forget. when a key was pressed, it stopped scanning rows, asserted a key-ready output (with the key scanner stopped on the correct row and a 74xx138 encoding the column), and turned on a beeper until the key was acked by the processor. then, once the key was released by the operator, scanning continued. such KISS arrangements are far from uncommon in disco logic designs such as this and the Apple II, where processors were slow and had more important things to tend to than n-key rollover. it made a lot more sense when a system's IO was typically in the form of 74xx373 devices on the system data bus and you could use address decoding to drive state transitions

>>1691761
and you don't have to stick your thumb up your ass while you wait, either. just sample at 10ms intervals and logically combine the previous state with the current state. instead of the logical-AND used here, one can use logical-OR for faster response if the switches are constructed such that they won't accidentally unless positively operated. using a timer is a neat way to do it during low-power states tho

>>1691769
I believe they've instituted a minimum charge schedule for shipping and don't do actual cost anymore