[Elecraft] K2 Keyboard Theory

k7hbg at dslextreme.com k7hbg at dslextreme.com
Sat Aug 20 15:47:14 EDT 2005


Good day all!
 I was trying to understand how the keyboard signaled the controller
processor that a new key was punched but to no avail. Also, the shift
reg. (U2) notes which keys are pushed but I can't see how this works. The
inputs of U2 are pulled up with external 100k r's but the input of U2
being a 'hc device loads the input circuitry very very little and so the
input would never go to a low logic level.
 I take it that until the processor is some how notified that a key is
pushed, it remains in sleep mode. Hard for me to understand without some
help but I'm sure, you guys have the answers.
 Thanks for any encouragement, Bob K7HBG





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