I'm building an electronic drum set and I need more than 8 analog inputs, so I can't use a single 4051 multiplexer. Since some of the consecutive hits on a single sensor (say the snare drum for a drum roll) will be fast, I'm looking for the fastest method of multiplexing, so that each hit is registered.
Also, if anyone has any other suggestions to ensure that each hit is registered, please fill me in.
Thanks!
Just use more multiplexers. you can have up to eight multiplexed outputs going to another multiplexer. You cycle through the first multiplexer and then the next and then the next. Basically you multiplex the out puts of your multiplexers. This gives you sixty four inputs with six control lines. Three control lines for the 'master' multiplexer (the output of which goes to your arduino) and three that are shared by the eight input multiplexers (the outputs of which go to the eight inputs of the master multiplexer) . I'm fairly sure it can run fast enough for musical proposes, if you are using switches you might also need to debounce them and this is were you are likely to see latency.
so I can't use a single 4051 multiplexer
You can run one multiplexer on each analogue input, this shows two being used but you get the idea:-
http://www.thebox.myzen.co.uk/Hardware/MIDI_Footsteps.html
However, the more you have the longer it takes to get round them all. It is not so much the switching time but the settling time. If you have enough to trigger a logic input you could put a port expander on the SPI bus the MCP23S17 is typical. This would have 16 inputs and could be set to trigger an interrupt when any input changes state. The interrupt service routine then gets the data from the chip to see which input changed. You can have up to 8 of these chips on the SPI bus without any further work.
Thank you both for your suggestions. I think I'm going to use two 4051's to allow for future expansion.