Building an Input register Pt 2
Having built my keyboard See here . I went on to build the actual input module. Firstly here are the parts I intended to use (the final design is different!) The list is 1 x 74C922, 2 x AM2918 Russian clone 2 x DM9368 hex to 7 segment driver and a 2 digit display bought during Maplins' closing sale. The first attempt has 1 x AM2918 and 1 x DM9368 driving one half of the display. The 4 single LED's are used to indicate which key has been pressed. However something odd happened with this version, the 7 segment display showed key presses 1 press delayed. What do I mean? On power up the display would show '0'. On the first key press the single LED's would change, e.g. if I pressed 3 the right hand 2 would light, but the display would stay at '0' The next press e.g. 7 would cause the right 3 LED's to light, and at the same time the display would change to '3'! This turned out to be completely repeatable and consistent. Puzzled I dug out th
