Re: keypad controller
- From: Spehro Pefhany <speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 31 May 2005 14:32:31 -0400
On Tue, 31 May 2005 19:23:31 +0200, the renowned Michael Lange
<leckmich@xxxxxxxxxxxxx> wrote:
>Hi you,
>
>> I want to implement a 6x6 matrix keypad controller in hardware which
>> should be able to detect multiple key presses.
>> Can anybody suggest how to go about this??
>
>if you mean more than one key pressed same time, you could use this.
>(Please expand to 6x6 matrix). Set the Y-lines to high, only one at same
>time, and read the X-lines to get the pressed key(s) in this row.
>
> Y0 o Y1 o Y2 o Y3 o
> | T | T | T | T
> | --- | --- | --- | ---
> o--o o-->|--. o--o o-->|--. o--o o-->|--. o--o o-->|--.
> | | | | | | | |
> X0 o---)-----------o-)-----------o-)-----------o-)-----------o-
> | T | T | T | T
> | --- | --- | --- | ---
> o--o o-->|--. o--o o-->|--. o--o o-->|--. o--o o-->|--.
> | | | | | | | |
> X1 o---)-----------o-)-----------o-)-----------o-)-----------o-
> | T | T | T | T
> | --- | --- | --- | ---
> o--o o-->|--. o--o o-->|--. o--o o-->|--. o--o o-->|--.
> | | | | | | | |
> X2 o---)-----------o-)-----------o-)-----------o-)-----------o-
> | T | T | T | T
> | --- | --- | --- | ---
> o--o o-->|--. o--o o-->|--. o--o o-->|--. o--o o-->|--.
> | | | | | | | |
> X3 o---)-----------o-)-----------o-)-----------o-)-----------o-
> | | | |
> | | | |
Perhaps obvious, but you do need some pull-down resistors on the X
lines. Less obviously, there is an RC time constant between the stray
capacitance and the resistors you choose (when the line is going low),
so you might want to have the processor twiddle its thumbs for enough
time to let the voltage settle. Maybe a microsecond or so with 10K
(assuming short connections), proportionally longer with higher
resistances.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.
- References:
- keypad controller
- From: praveen . kantharajapura
- Re: keypad controller
- From: Michael Lange
- keypad controller
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