ON 20050118@5:58:05 PM at page:
http://techref.massmind.org/techref/io/keyboard.htm#38370.7486689815
James Newton[JMN-EFP-786] Says
Uche Nwoko of Multi-Electronics Design Says:
A simple experiment for those looking for, a common keyboard that is capable of encoding 9 key strokes into four binary bit. what I did was to use an IC 74HC147, known as 10 to 4 line priority encoder, as a keyboard to controle a wireless remote system, with this IC I can be able to achive an Output of 4 binary code from 0 to 9, whereby i interface the binary output with any encoder to give me the right data i needed to controle my design.
To construct a keboard from 74Hc147 all 1 to 9 input pins should pull high with 10k resistors, then each of the input is connected to micro push buttons,with this buttons i can be able to sellect any of the input from 1 to 9, if all of the 9 iputs are on high position, the output will be Automatically 0 (Zero), i.e if the output is invert, that is why I did not have 0 button on my keboard, with the help of cd4511 you can be able to read out the output from 7 segment display.
Below is the input and Output Table.
A B C D 1 2 3 4 5 6 7 8 9
1 1 1 1 = 1 1 1 1 1 1 1 1 1 when output invert = 0, if not invert = F
0 1 1 0 = 1 1 1 1 1 1 1 1 0 when output invert = 9, if not invert = 6
1 1 1 0 = 1 1 1 1 1 1 1 0 1 when output invert = 8, if not invert = 7
0 0 0 1 = 1 1 1 1 1 1 0 1 1 when output invert = 7, if not invert = 8
1 0 0 1 = 1 1 1 1 1 0 1 1 1 when output invert = 6, if not invert = 9
0 1 0 1 = 1 1 1 1 0 1 1 1 1 when output invert = 5, if not invert = A
1 1 0 1 = 1 1 1 0 1 1 1 1 1 when output invert = 4, if not invert = B
0 0 1 1 = 1 1 0 1 1 1 1 1 1 when output invert = 3, if not invert = C
1 0 1 1 = 1 0 1 1 1 1 1 1 1 when output invert = 2, if not invert = D
0 1 1 1 = 0 1 1 1 1 1 1 1 1 when output invert = 1, if not invert = E
The above table is exctly how the input and out out look like, if necessary the output can be invert with the help of Ic CD4069 or CD4049, I wish any reader a success, if you want to try this simple design.
ON 20050118@5:59:08 PM at page:
http://techref.massmind.org/techref/io/keyboard.htm#
James Newton[JMN-EFP-786] edited the page. Difference:
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ON 20050125@10:13:00 PM at page:
http://www.piclist.com/techref/io/speech.htm#38377.9256944444
James Newton[JMN-EFP-786] Says
/techref/fileext/gsms.htm
GSM Audio