Hardware revision changes for Olimex PIC-IO
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Hardware revision D - major improvements of the design

- PCB now two has layers;
- Routing improved so no wires go under relays and optocouplers;
- Replaced PTH components with SMD size;
- A lot of components replaced with better ones; 
- RS moved towards the middle;
- PWR jack replaced with the typical for Olimex boards;
- Added two mount holes for easier attachement to own boards.

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Hardware revision C1

R1, R2, R3, R4 changed from 330 to 470 Ohm since 24-1.2-1.2/330=0,065A which is more than the max for the optocoupler, and 470 Ohm max current is 45mA which is fine (max current for optocoupler is 50 mA)

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Hardware revision C

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1. Added white print logos for PB-free, antistatic notice, recycle notice.