PLease do not send Word attachments. Can you resumit as text/gif Stuart ----- Original Message ----- From: "Carey Fisher - NCS" To: Sent: 14 April 2003 06:07 Subject: Re: [OT:] different approach to keyboard scanning? > Would you believe you can read 75 switches with 5 I/O lines? Check out the > attached Word doc. It has a couple methods for reading many switches with > few I/O lines. > > > ----- Original Message ----- > From: "Herbert Graf" > To: > Sent: Saturday, April 12, 2003 6:37 PM > Subject: Re: [OT:] different approach to keyboard scanning? > > > > Wow, thanks for the summary, I didn't notice this thread until now. That > is > > an excellent design! 10keys with only 4 I/O ports used!?? Gonna file this > > one in my "info" file... TTYL > > > > > -----Original Message----- > > > From: pic microcontroller discussion list > > > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of James Newton, webhost > > > Sent: April 12, 2003 18:03 > > > To: PICLIST@MITVMA.MIT.EDU > > > Subject: Re: [OT:] different approach to keyboard scanning? > > > > > > > > > source= http://www.piclist.com/postbot.asp?id=piclist\2003\04\11\174744a > > > > > > Let me see if I have all this right. Combining Scott and Eric's > > > comments you > > > could do this: > > > > > > 0 1 2 3 GND > > > | | | | | > > > 0---+--KEY-KEY-KEY-KEY- > > > | | | | | > > > 1---+---+--KEY-KEY-KEY- > > > | | | | | > > > 2---+---+---+--KEY-KEY- > > > | | | | | > > > 3---+---+---+---+--KEY- > > > | | | | | > > > > > > Weak pull-ups enabled, first read the port and check for any lows, this > > > would be a key on the GND (far right) column. If all pins are high, > ground > > > pin 0 and any lows on 1 thru 3 would be a key in the top row. > > > Then ground 1 > > > and a low on 2 or 3 indicates the two keys on the second row > > > (other than the > > > last column), finally ground 2 and check the remaining key (on the third > > > row) by reading back 3. > > > > > > That is a 10 key pad in 4 IO lines with no external components other > than > > > the keys. > > > > > > --- > > > James Newton: PICList.com webmaster, former Admin #3 > > > mailto:jamesnewton@piclist.com 1-619-652-0593 phone > > > http://www.piclist.com/member/JMN-EFP-786 > > > PIC/PICList FAQ: http://www.piclist.com > > > > > > -- > > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > > > > -- > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.