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[Gumstix-users] Audiostix II -R781

From: Gordon Kruberg <gordon@gu...> - 2006-03-26 00:10

Thanks for the suggestions.  My commetns and status are below.

- How about moving the connector labels on the silkscreen so that they 
are still visible after the board is populated?  Printing "audio in" and 
"audio out" somewhere would be even better.
Done.

- It would be nice to have an optional null resistor or jumper between 
USB_VBUS and V_BATT, unless there is a good reason to
never connect them (?).
Done: labelled FB4

- Similarly, how about an optional jumper between V_BATT and AD0 ?  (The 
UCB400 has internal resistive voltage dividers on ADx.)
Not done, subject to my understanding a bit more about the goal.  
Question I have is whether this was really for V_Batt (vs. AVdd or Vcc)

- Still would like to see a LCD bias generator on board.  Better yet a 
MAX3325 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2117  
<http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2117>RS-232 and LCD bias!
Great idea: Not being implemented on this version primarily due to 
connector size and power plane issues (i.e. where do I put them?)


- The extra I/O pins and A/D channels from the UCB1400 should be brought 
to connector or at least to pads/vias so we can solder to them.
Done: I am interested in seeing how noisy these will be, but they're there.

- I would highly recommend considering the LEA-4H with SuperSense.  It's 
only $10 more and it is a very sensitive engine. We've been using it for 
a while and have been very pleased with its ability to resolve with very 
weak signals.
In process-- I need to see the docs to know what changes are needed.

Gordon

Re: [Gumstix-users] Audiostix II -R781

From: Pascal A. Brisset <pascal.brisset@wa...> - 2006-03-26 02:14

Gordon Kruberg writes:
 > - Similarly, how about an optional jumper between V_BATT and AD0 ?  (The 
 > UCB400 has internal resistive voltage dividers on ADx.)
 > Not done, subject to my understanding a bit more about the goal.  
 > Question I have is whether this was really for V_Batt (vs. AVdd or Vcc)

Definitely V_BATT.

Section 11 of the UCB1400 datasheet says "... This makes these
analog inputs very suitable to monitor battery voltages."
Section 15 says the input range is 7.5 V.

Disclaimer: I haven't actually tried it. But it looks like these
inputs are really intended for battery monitoring. The idea would
be to allow a system to do something before the CPU is undervolted
or before LiPo batteries get overdischarged.

-- Pascal

RE: [Gumstix-users] Audiostix II -R781

From: David Vescovi <dvescovi@ta...> - 2006-03-26 12:19

Pascal is correct. The designs I have seen use the A/D channels on the
UCB1400 for things
like battery management, supply monitoring etc. The digital IO is usually
used for things like turning the backlight of an LCD display on/off and
enabling/disabling voltage regulators for various peripherals etc.

DV

-----Original Message-----
From: gumstix-users-admin@...
[mailto:gumstix-users-admin@...] On Behalf Of Pascal A.
Brisset
Sent: Saturday, March 25, 2006 9:14 PM
To: gumstix-users@...
Subject: Re: [Gumstix-users] Audiostix II -R781

Gordon Kruberg writes:
 > - Similarly, how about an optional jumper between V_BATT and AD0 ?  (The
> UCB400 has internal resistive voltage dividers on ADx.)  > Not done,
subject to my understanding a bit more about the goal.  
 > Question I have is whether this was really for V_Batt (vs. AVdd or Vcc)

Definitely V_BATT.

Section 11 of the UCB1400 datasheet says "... This makes these analog inputs
very suitable to monitor battery voltages."
Section 15 says the input range is 7.5 V.

Disclaimer: I haven't actually tried it. But it looks like these inputs are
really intended for battery monitoring. The idea would be to allow a system
to do something before the CPU is undervolted or before LiPo batteries get
overdischarged.

-- Pascal