Laptop keyboards - Page 1
Forum section: electronics / beginners

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 02, 2013, 10:05:30 pm
content: Hello, i have a small netbooks keyboard here and i am unsure how it works?Its a nice small and compact keyboard with a little ribon cable with k6107 writen on it.How does it determin what keys are being pressed and how would i go about connecting it to a microcontroler to send serial data to it?

author: madires
author_rank: Super Contributor
timestamp: June 02, 2013, 10:17:06 pm
content: Please seehttp://pcbheaven.com/wikipages/How_Key_Matrices_Works/!

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 02, 2013, 10:31:37 pm
content: Thank youSo in my case:The first 10 pins could be inputs and the pins on the right could all be the outputs correct?

author: madires
author_rank: Super Contributor
timestamp: June 03, 2013, 12:38:21 am
content: Quote from: carbon dude oxide on June 02, 2013, 10:31:37 pmMight be possible. Check some keys with your DMM and you'll know.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 03, 2013, 05:47:52 am
content: Thats fine i was thinking maby have a small micro to decode it and output a serial to the main micro, that was i can get something like an atmeltiny with enough inputs that this needs and juat output it there ^.^

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 03, 2013, 10:46:57 am
content: I have tried doing a continuity test on te space bar but none of the lines connect. Could it be that there is too high of a resistance and that i would have to send a voltage down to find out?

author: madires
author_rank: Super Contributor
timestamp: June 03, 2013, 01:11:25 pm
content: Quote from: carbon dude oxide on June 03, 2013, 10:46:57 amMost keyboards are based on switch contacts of some sort. High quality keyboards got microswitches and cheap/small stuff got conductive pads. Of course there are other technogies too, like capacitive, but those are rarely used for computer keyboards. Please try another key too. Or put something on the keyboard to have several keys pressed. If you still don't get anything it could be some other technology.BTW: Atmel got a nice application note for matrix keyboards athttp://www.atmel.com/Images/doc2532.pdf.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 03, 2013, 02:45:33 pm
content: I tried the link but it does not exist, im going to give the keyboard another go in a bit.

author: deephaven
author_rank: Frequent Contributor
timestamp: June 03, 2013, 03:14:17 pm
content: Quote from: carbon dude oxide on June 03, 2013, 02:45:33 pmIt's the dreaded full stop at the end of the URL syndrome. Tryhttp://www.atmel.com/Images/doc2532.pdf

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 03, 2013, 07:57:59 pm
content: I have been probing the ribbon cable on the graphite uaing my multimeter. Is it better to have it connected to a pcb connector and then the metal contacts on there?

author: madires
author_rank: Super Contributor
timestamp: June 03, 2013, 08:52:26 pm
content: Quote from: carbon dude oxide on June 03, 2013, 07:57:59 pmThe end of the cable facing the laptop should be tinned. Aren't you probing at that end?

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 04, 2013, 07:41:42 am
content: There is no tinning, its still ot the conductive black traces

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 04, 2013, 08:59:26 am
content: I did truly to do a continuity teat on a different ribbon keyboard (NSK-HAA0U) from a hp g60But i could not get any continuity readings from any of the contacts. Do i have to apply a voltage down the ribbon cable or it to work?

author: C
author_rank: Super Contributor
timestamp: June 04, 2013, 09:16:17 am
content: matrix, like x horizontal and y vertical lines. where lines cross is a possable switch location.if you are testing two x lines you will not see a one button press.connect to two pins, press all keysonly shift one connection until you have tested all pins an only then shift the other connectionrepeat

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 04, 2013, 09:18:15 am
content: I was doing it the other way round, hold one key and test all pins to eachother, i shall try your way now

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 04, 2013, 09:45:10 am
content: Ok after further testing i have found out that the resistance over the ribbon cable and keys is too much for my multimeter to make a sound but it does return a reading on the screen when its got a connection, i found the number pad 5 digit and ; with readings but no soundIm going to be here a while to figure out the connections now

author: C
author_rank: Super Contributor
timestamp: June 04, 2013, 04:43:12 pm
content: Strong hint,Some times they make it easy for the software side to decode the matrix.Some times they make it easy for the PC board to be setup as a matrix.Some like nice logical pin-outs on the connectors.I would not be surprised for one of the two pins you found connects to the 5 to also connect to the other numbers.C

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: June 04, 2013, 05:50:11 pm
content: Ok i have another keyboard which i have found which has 8 power lines to switch and 20 data lines to read.Thats probably not the right names for both of them but yea.What atmel controler would be good for this? It needs to output the key press via a serial connection.

author: C
author_rank: Super Contributor
timestamp: June 04, 2013, 06:56:43 pm
content: There are many ways to do a keyboard matrix with a micro. With external shift registers you can get down to a very low pin count on the micro. As the need for speed increases a parallel choice may be better.Read app note and look at link to wikipediahttp://www.atmel.com/Images/doc1231.pdfC