Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

foil keyboard

Topic last updated 16 Jan 2012, by Rene Greiner. 2 replies
Richard Wurzer
16 Jan 2012

http://www.google.at/imgres?q=folientastatur&um=1&hl=de&client=firefox-a&sa=N&rls=org.mozilla:de:official&biw=1280&bih=831&tbm=isch&tbnid=2mhTgiBYaSnBmM:&imgrefurl=http://shop.e-lab.de/products/de/Module-Boards/DisplaysKeyboards/Folien-Tastatur.html&docid=q7P-joGIlBdBoM&itg=1&imgurl=http://shop.e-lab.de/images/product_images/info_images/KeyboardF.jpg&w=200&h=150&ei=PRwUT6WXKOik4gS3pPC_Aw&zoom=1

I want to program a foil keyboard but I do not identify the foil keyboard has 13 pins i think the first pin is Vcc and the other pins is for numbers :*,0,#,1,2,3,4,5,6,7,8,9

X M
16 Jan 2012

Don't panic ! it is a simple switch matrix. ( normally said 4x4 matrix Keyboard , yours seems to be 4x3 ) Using an ohmmeter you can identify the columns and rows .... Look at the manufacturer documentation !!! http://www.e-lab.de/diverse/KeyBoardF.pdf

Rene Greiner
16 Jan 2012

Wow that's efficient use of mbed pins. Needs normally 12 input pins. But hey, with a simple trick just 1 pin is needed.

Connect Vcc with mbed analog input pin and connect the other pins with resistors in series.

  • -R1-0-R2-#-R3-1-R4 .... with all resistors the same value. Measure the voltage on your input pin and you can calculate the key which was pressed