Timeline for How can 16 buttons be connected with only 8 wires?
Current License: CC BY-SA 3.0
22 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 8, 2017 at 14:37 | comment | added | woliveirajr | The manual of your product teaches how to demultiplex it: gotronic.fr/pj2-sbc-buttonmatrix-fr-1461.pdf | |
| Mar 8, 2017 at 9:15 | comment | added | Chris H | @MarceloEspinozaVargas the device on the left is a Raspberry Pi (model 3). Those GPIO pins are configurable quickly and easily in code. It looks like all pins of the keypad are connected to GPIOs (nothing to GND) but the marked up photo isn't all that clear | |
| Mar 8, 2017 at 6:20 | answer | added | Darrell Harriman | timeline score: 0 | |
| Mar 8, 2017 at 4:31 | comment | added | slebetman | Check out this animation: upload.wikimedia.org/wikipedia/commons/f/f2/… (note: the switching in row and column is not a hardware thing. It is your code going "OK, now set pin1 to high, now read what's the state of pin5" etc.) | |
| Mar 7, 2017 at 22:51 | comment | added | Nick T | deskthority.net/wiki/Rollover,_blocking_and_ghosting | |
| Mar 7, 2017 at 21:43 | comment | added | Matthew Whited | cs.ucr.edu/~ehwang/courses/cs120b/04summer2/labs/lab9.html | |
| Mar 7, 2017 at 21:07 | history | tweeted | twitter.com/StackElectronix/status/839220892462956544 | ||
| Mar 7, 2017 at 19:05 | history | edited | JRE | CC BY-SA 3.0 |
edited title
|
| Mar 7, 2017 at 18:48 | answer | added | Harper - Reinstate Monica | timeline score: 9 | |
| Mar 7, 2017 at 18:18 | comment | added | Gábor | @Basj: having multiple presses is not a problem. You scan all four lines one after the other. If a button is found pressed in line 1, you note it. When it comes to line 3, you find another button pressed there, you note it, too. In the end, you get both buttons. As long as you're able to scan significantly faster than people can press buttons, you won't miss it. | |
| Mar 7, 2017 at 14:42 | comment | added | Basj |
I'm sorry @TonyM but it's probably easy to read for someone who already knows, but for me, seeing assembler and MOV A,@0X11;disable WDTis not particularly simple to understand how a keypad with multiple-button-presses-at-same-time works...
|
|
| Mar 7, 2017 at 14:38 | comment | added | TonyM | Sure :-) www.emc.com.tw/eng/database/Sa2/Gp/An/Gf/AN-009.pdf | |
| Mar 7, 2017 at 14:35 | comment | added | Basj | @TonyM Thanks for pointing me this. Can you link the PDF instead of making a mystery ;)? Maybe I searched with other keywords than keypad, etc. and I probably didn't find the same. | |
| Mar 7, 2017 at 14:33 | comment | added | TonyM | I did that search and the second result was a pdf answering in detail your Q1, Q3 and part of Q2. You can see my point, can't you - this is already documented and better than we will explain it here. Take a look, you'll get detailed answers. | |
| Mar 7, 2017 at 14:32 | answer | added | bobflux | timeline score: 1 | |
| Mar 7, 2017 at 14:25 | comment | added | Marcelo Espinoza Vargas | It depends on the actual multiplexing code, if it's as simple as sending +V across every row and use each columns as an input then it won't be able to do it, but if it switches around every row and column (taking all 8 pins as input and output) and can hold on memory what button is pressed it may be able to detect multiple buttons pressed at the same time | |
| Mar 7, 2017 at 14:22 | answer | added | Olin Lathrop | timeline score: 23 | |
| Mar 7, 2017 at 14:21 | comment | added | Basj | @MarceloEspinozaVargas Ok. Then what do you think about question #2 ? | |
| Mar 7, 2017 at 14:20 | comment | added | Marcelo Espinoza Vargas | The device on the left must have a code of multiplexing inside it | |
| Mar 7, 2017 at 14:15 | comment | added | Basj | @TonyM Of course I did, many searches, and I even ordered a few multiplexer chips 74HC164 that arrived at home a few days ago. I was about to wire everything with this multiplexer chip when I found this. Then I was wondering "how can this work without any multiplexer" ? | |
| Mar 7, 2017 at 14:10 | comment | added | TonyM | This is common knowledge as you'll find with a Google search for 'keypad multiplexing' or suchlike. Did you not try that first, before posting this? | |
| Mar 7, 2017 at 14:05 | history | asked | Basj | CC BY-SA 3.0 |
