[Discuss-gnuradio] New FrontEnd Schematic & Layout

[cfk]

Dear Guys:

    I have added a dual opamp (LT1678) to take aux_dac_a to the first tuner
agc input and aux_dac_b to the second tuner agc input with a voltage gain of
2. I also put I2C level shifter circuit into the schematic.

    The way the programming of the I2C address works is that if pin 11 is
grounded, the tuner responds to an address of 0xC0. If that same pin is left
open, it responds to an address of 0xC2. If that pin is held halfway between
ground and +5V, it responds to an address of 0xC4 and if the same pin is
connected to +5V, it responds to an address of 0xC6.

    So with the one pin, they get four different states from it.

    The board is still double sided with most of the traces on the component
side. The solder side ground is beginning to get a bit chopped up and things
are getting tight with the additional circuitry. There are about 10 routes
not yet connected. They are mostly the I2C level shifter that I added today
while I was pretending to work.

    In any case, the four links for schematic page 1, page 2, component side
layout and solder side layout.

http://home.pacbell.net/cfk/frontend4702_1.pdf
http://home.pacbell.net/cfk/frontend4702_2.pdf
http://home.pacbell.net/cfk/frontendlayoutcomponent.pdf
http://home.pacbell.net/cfk/frontendlayoutsolder.pdf

    If I could figure out how to tell Acrobat Distiller (in windows, of
course), how to not print the funky stippled background, I would. I have
tried white background. Then I tried black background. Both to no avail. I
would have thought one of them would get rid of the background stippling,
but oh well.

Charles