crosstalking in megadrum

[Itamar_M]

hello
i have build the synthex 2.7v pcb board , and when i try testing it , it seams that triggering one drum it triggers some more 10 inputs , depends how strong i hit.
all other inputs are disconnected. also when i'm powering on the board , one input is minimally triggerd by it self and when i'm touch the board a few tims it disappears.

there are some ideas ?

thanks!

[dmitri]

viewtopic.php?f=3&t=352

[Itamar_M]

Hey
My pcb is synthex 2.7V with 32 inputs. the mcu is atmega32 (16PU) , the crystal frequency is 20Mhz , the firmware version is 20091217 (megadrum32_20_32_20091217).
i'm using midi over usb with pic18f2550 and 12Mhz crystal.
the drum pad is home made from a drum shell with piezo triggers.
i tried the 4558 and the 74hc4851 multiplexers , and both showing the same result of crosstalk to about haft of the inputs , but it depends how strong i hit.
the loaded settings is the default that came with the firmware.
i'm using the usb port as power supply.
when i testing the module, only one drum pad is connected and no hh pedal connected.
any details i forgot?

Thanks!

[dmitri]

So, is it MAX4558 or 74hc4851 at the moment?

[Itamar_M]

hey
right now the 74hc4851 connected.

thanks!

[dmitri]

Make sure that 4851s are properly soldered or sitting sitting tight in sockets.
Make sure that resistors on the ADC inputs of Atmega (pins 34-40) are in fact 4k7 and not more (47k by mistake?).
Make sure the ground wire from the piezo is properly connected.