MCP23008 IO Expander - Demultiplexer

 

Module sizing considerations

http://www.blogger.com/blogger.g?blogID=1840459474737789074#editor/target=post;postID=4984270296873400858

Now I have soldered the MCP23008 GP0 ~ GP7 bus wiring, from MCP23008 side to 2 HC573.  There are 8 wiries x 2 = 16 wires to do.  If each point to point soldering takes 3 mintues, then the whole job is about 45 minutes, and including resting time, 16 point to point soldering is about 1 hour's work.

I now find this small protoboard is almost optimum as a hardware modules.  I once thought about using a bigger size board and squeeze in 4 HC573, or even using a still bigger board and place 8 HC573 on board.  But I think that would be difficult to divide the work into reasonably times parts, say within one hour for 16 point to point soldering.

Another contrainst is that if I need to use 8 LEDS for each HC573, then even a much bigger board would be tight to space in 32 LEDs and the wring would include too many crossovers and again too awkard to handle.

And for a 2 buffer board, the coupling is loose enough to do swap testing.

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