should I use capacitor between gnd & Vcc ?? how could I calibrate them?
It's always a good idea to have some. Normally a little one to get rid of high frequencies (0.1uF to 0.01uF) and a big one for the DC response like 100uF or bigger. It's not too critical, you can have too little but not too much
I saw a lot of kind of capacitors.
on the monome schematic, there are 2 capacitors both about 0.1uF.
http://docs.monome.org/lib/exe/detail.php?id=tech%3Asource_files%3A40h%3Athrulogic_schem&cache=cache&media=tech:source_files:monome40h_thrulogic_schem.png
There are 2 others very near of MAX7221:
- 10uF (and polarised)
- 0.1uF
may I use 2 same capacitors 0.1µF for gnd/Vcc from arduino AND from my power supply?
Any way you like, I normally run another wie from the PSU but you can link from the PCB. It's not too important as there is not a lot of current being drawn on this connection but it needs to be connected to provide a reference for the switching signals.
all gnd together on the PCB, I guess it would be ok!
wow my eagle schematics begins to be ready... I have to send it to 4PCB ....
I hope I didn't make any mistake..
I have a little problem because I don't know how to create 2 different Vcc... but... :o