First you have to figure out what the problem is.
What are the capacitors for?
Why do you write to the output ports multiple times?
QuoteIt would take about 8.2ms just to put the data to the column shift registers plus the time i need to get that data from the other arduino (an other 8.2ms at best) which kinda limits my refresh rate.I am not sure how your have structured your hardware but it takes about 0.1ms to shift a byte into a HC595, on a 1MIPS AVR, and much faster if you use hardware spi.To drive 64 leds, you need to shift at most two bytes and that should be no more than 0.2ms, and likely much lower than that if you are running your chip at 16MIPS.As fungus has pointed out, your hardware doesn't make a whole lot of sense to me and you may want to rethink how you approach the whole thing.
It would take about 8.2ms just to put the data to the column shift registers plus the time i need to get that data from the other arduino (an other 8.2ms at best) which kinda limits my refresh rate.
its 64x64=4096 leds
Quote from: fungus on Oct 18, 2012, 08:50 pmWhat are the capacitors for? It looks to me like they might be keeping the LEDs lit up for a short time after your MOSFET switches off.for exactly that
What are the capacitors for? It looks to me like they might be keeping the LEDs lit up for a short time after your MOSFET switches off.
I still think they're the problem, not the MOSFETs. The cathodes all seem to be joined together when they arrive at a MOSFET, Is it possible that charge from the capacitor is leaking into other LEDs via. that junction? If so you need to put more diodes in there to prevent it.If you want smaller capacitances in your MOSFETS you probably have to use smaller ones. T220 MOSFETS have a big chunk of silicon inside them so capacitance is always an issue. You can try something like a VN1206L which comes in a T0226.An oscilloscope would solve this mystery far, far faster than debating in forums...
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