Keypad and LCD to BS2px
mph
Posts: 13
I am working on interfacing a 5x4 keypad and a 2x16 LCD (with Hitachi 44780) to my Basic Stamp BS2px with both the LCD and the keypad sharing the same pins. I closely followed the schematic published in "Nuts&Volts (Volume 4): Column #97: Keyboard Entry and Display". The only difference is that I am using the 74C923 keypad decoder (for 5x4 keypad) instead of the 74C922 decoder (for the 4x4 keypad) shown in the article.
The keypad entry works just fine. Writing to the LCD however causes problems for particular characters such as "2" and "4". Occasionally they are output OK, but mostly writing these characters just causes the cursor to move, sometimes erratically. LCD output works fine if the keypad circuit is disconnected from the BS2px pins. So there is some interference going on.
Any thoughts what might be causing it?
Tnx!
mph
The keypad entry works just fine. Writing to the LCD however causes problems for particular characters such as "2" and "4". Occasionally they are output OK, but mostly writing these characters just causes the cursor to move, sometimes erratically. LCD output works fine if the keypad circuit is disconnected from the BS2px pins. So there is some interference going on.
Any thoughts what might be causing it?
Tnx!
mph
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