0
\$\begingroup\$

After trying a lot on QTouch Matrix for ATmega8,It didn't work for me. So sharing the trouble here.

I have taken reference from this beautiful article. Here he had provided a schematic and PCB design also. I have followed the same schematic and PCB layout, used same code for ATmega8 @16MHz crystal and with fuse bits: 0xc9ff, still it is not working at all. I got calibrating message on terminal, then after that, when I touch the Pad, it displays random numbers on terminal and that was only for three keys! others are not working. also those three keys are not working covering with a plastic sheet.

If somebody can direct me towards right path and give some tips, it would be better for me to move ahead.
schematic diagram: enter image description here I have set up ATmega8 on General Purpose PCB. touch Pad is connected through jumper wires.Below are Images of the test setup. MATRIX PAD: enter image description here MATRIX PAD Wiring: enter image description here TEST SET UP: enter image description here ATmega8 Board: enter image description here

\$\endgroup\$
  • \$\begingroup\$ How much capacitance do you think those long wires can pick up? \$\endgroup\$ – Ignacio Vazquez-Abrams May 5 '15 at 15:15
  • \$\begingroup\$ Long wires may be the issue? \$\endgroup\$ – isoln May 6 '15 at 5:17
  • \$\begingroup\$ thanks Ignacio Vazquez-Abrams for the comment. there may be one of the problem, but I have read few lines from the article mentioned above, from which i inspired to do this , says: "There's a little problem however. All AVR inputs are protected from overvoltage by the internal Shottky diodes which have very low bandgap of 0.2V. This puts a serious constraint on the design: |quant.suff | should be not above 0.2V, or nothing will work out at all." Can anybody explain me this please? \$\endgroup\$ – isoln May 6 '15 at 5:59
  • \$\begingroup\$ I thing there is a PCB design fault. I am designing new layout for QTouch Matrix touch pad in altium design software. \$\endgroup\$ – isoln May 7 '15 at 14:25
2
\$\begingroup\$

You have missed the jumpers to join "Y-wires". If you look at page2 fig4 image closely and read the fig4 text in the: QMatrix™ Technology White Paper

enter image description here

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.