Buttons 1-4 double 5-8

[Guest Matthias]

Hello!

I am experiencing a problem with the 8 buttons of my MIDIBox 16, running on a 16F874-20 PIC. Buttons 5-8 work as they should, but if I press one of 1-4, the equivalent of the second four is also pressed (electronically). That means, if 1 press button 1 e.g., two MIDI messages are sent, those assigned to buttons 1 and 5. Same with 2 and 6, 3 and 7, 4 and 8.

Does anybody know what I can do about it? Thorsten already said in reply to an earlier forum posting I did he wanted to write something about it in the FAQ, since he needed to explain a couple of things about this problem.

Who else has made the same experience? Who knows what one can do to solve this malfunction? Has anyone found an explanation by Thorsten?

Thanx in advance,

Matthias

[TK.]

Hi Matthias,

the explanation for the problem can be found here:

http://www.ucapps.de/midibox/midibox_plus_16.pdf

Magnify the red text beside of the 8 additional diodes.

Best Regards, Thorsten.

[Guest Matthias]

Hi Thorsten,

thank you very much for your quick reply. Trouble is only, that it also appears to me if I press only ONE button. I did not really intend to use several buttons at the same time like a sort of "piano with eight programmable keys". I only press button 1, and the message assigned to no. 5 is sent as well. The display also shows these asterisks for both buttons. But it does not appear when I press button 5, so RD0 and RD1 cannot be connected unintendedly(does that word exist?).

Any other suggestions? Or might it work with the diodes nevertheless? I already wonder where there might be enough space on the vectorboard left to implement 8 more diodes...

Hope to hear from you soon,

bye,

Matthias S.

[TK.]

Hi Matthias,

I think that your PIC is damaged. The diodes might help, but I cannot give any success guarantee... don't waste PCB area for the diodes, just solder them directly to the buttons.

Best Regards, Thorsten.