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Re: Lexicon 200 problem help need

Couldn't find any 200 in their product catalog, even legacy. They have the MX200 and MXP200, but no keyboard... Need it to be able to help you...
2 questions: did you check the row outputs of these buttons. Since they ohm out ok and since they are likely on the same row, seems they are not fed by the demux (demultiplexer). Check it out at the colon column.
It works this way: to use the fewer wires possible, one of the switches contact on each column are connected together. The other switches contacts are connected with their row neighbors. Then each row is fed by its own sense signal, which is a pulse. The sense signals are organized in such a way that each row has it own delay for sending the pulse. The microcontroller senses the column outputs. When you press a button at coordinates (x,y), the µcontroller receives a sense signal on line (x), whose pulse is delayed in a (y) manner, so it can know line (x) and column (y). The different delays are built by a component called a demultiplexer (if not done in the µC), which receives a clock and a cycling row address and sends the clock only to the addressed row.
So: do each of your rows receive its sense signal? Can you see the sense signal from one of the column output when a button is pressed?
Oh, depending on the implementation, the roles of rows and column can be inverted. In this case, test the row output when a button is pressed.


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  • Re: Lexicon 200 problem help need - Jacques 03:03:31 08/30/05 (0)


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