SMT prototype progress

Well, the SMT prototype is almost working. There's some sort of bug (maybe) with the mikroProg programmer I'm using which seems to be ignoring the CPUDIV configuration fuse that I need. As a result the MCU clock runs at 48 MHz instead of 24 MHz...not good. The LCD shows that it is trying to establish a USB connection but not quite making it.

I put an OnSemi MC14066B Quad Bilateral Switch on the prototype (instead of the Maxim MAX4066 that I originally intended). The MAX4066 has a lower "on" resistance (around 45 Ω compared to about 100 Ω for the MC14066B at 5V) but it's probably more important that the "off" resistance is high - otherwise you could see weird behaviour. Still not tested yet, but in theory it should work.

Posted by Andrew Armstrong 2013-12-17

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