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Because almost all of the components are SMT, a
printed circuitboard is necessary for prototyping the design. The
board was layed out and hand-routed (!) using CADSoft's
EagleCAD. EagleCAD
is a freeware PCB-design software that runs on linux and windows
and can easily export Gerber files. An additional library is necessary
for the CS8900 chip and the isolation transformer. Board rev. 1
was printed by AP circuits,
using their rapid prototyping service. The board can be easily adapted
to use the free drills and does not have excessive vias.
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Almost all of the components required are obtainable
from Digikey or some other
components supplier. The CS8900A and the isolation transformer are
somewhat more difficult. A search on FindChips
or similar may reveal a stockist. The following parts are pin compatible
with the transformer:
- Vitec Corp #46Z248 SMD Isolation Transformer
- Bel Fuse Inc #S553-0716-00 SMT 10BASE-T Single Port Transformer
Module
- Halo Electronics Inc. #TG42-1406N1 SMD 10BASE-T SOIC Isolation
Modules
- Valor #ST7011 or #ST7010
Make sure to check the datasheet to make sure you're getting the right
transformation ratio, and SOIC outline! They run $5-$10. The CS8900A
is $10-$15. Sometimes samples can be obtained from the companies in
question.
All of the capacitors, LEDs and resistors are 1206 sized, and relatively
inexpensive. The 4.99K resistor must be 1%, but all of the other values
are 5%. The crystal package is quite pricey, at $6, and can be exchanged
for any oscillator desired. Per board cost for components should be
around $30. |
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Actually soldering the components is a non-trivial
task...
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