I am using the MSP430F42x with a static LCD.  Some units are failing
with many LCD segments coming partially on that should be off.  I have
tried replacing the micro and the LCD to no avail.  On the segments
that should be off I can see a pulse train of about 50mV PTP.
Perhaps there is a problem in the PCB, I can find none.  Failure rate
is about 5-10%.
I am wondering if anyone else has had this experience.

Thanks

Rich

Hi Richard,

It sounds like you have a code initialisation problem ?
Do you have the non-failing units running properly & displaying on LCD what
they should ?

I presume that with "static", you mean 2-mux ?
Check that all I/O pins assigned to (multiplexed) LCD segs are indeed set for
output,
and not floating.
Another possibility is that your frame frequency is way too high ? Check LCD
clock in MSP.
Too high a clock will cause crosstalk problems on the connection to segments,
and make segments
that are supposed to be off, light up erratically.

In "static" mode you should have voltages of 1/2 Vcc on the LCD, not
50 mV pp.
This also could point towards LCD clock being too high.

If this all fails, perhaps your LCD is too big, and you need more biasing
current in the
voltage divider.

Remember that an LCD should always be driven with AC, never DC (well, voltage,
not current :-)

B rgds
Kris


-----Original Message-----
From: msp430@msp4... [mailto:msp430@msp4...] On Behalf Of Richard
Sent: Saturday, 25 March 2006 4:47 AM
To: msp430@msp4...
Subject: [msp430] Strange LCD Behavior

I am using the MSP430F42x with a static LCD.  Some units are failing
with many LCD segments coming partially on that should be off.  I have
tried replacing the micro and the LCD to no avail.  On the segments
that should be off I can see a pulse train of about 50mV PTP.
Perhaps there is a problem in the PCB, I can find none.  Failure rate
is about 5-10%.
I am wondering if anyone else has had this experience.

Thanks

Rich







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Of course I meant with "static" that I presume the MSP is set to
apply
Vss-Vcc swing signals on one side of segment and 180 degree phase on other side
when "on",
as opposed to in phase when "off" on that segment, oops.

-- Kris

-----Original Message-----
From: msp430@msp4... [mailto:msp430@msp4...] On Behalf Of Microbit
Sent: Saturday, 25 March 2006 5:35 AM
To: msp430@msp4...
Subject: RE: [msp430] Strange LCD Behavior

Hi Richard,

It sounds like you have a code initialisation problem ?
Do you have the non-failing units running properly & displaying on LCD what
they should ?

I presume that with "static", you mean 2-mux ?
Check that all I/O pins assigned to (multiplexed) LCD segs are indeed set for
output,
and not floating.
Another possibility is that your frame frequency is way too high ? Check LCD
clock in MSP.
Too high a clock will cause crosstalk problems on the connection to segments,
and make segments
that are supposed to be off, light up erratically.

In "static" mode you should have voltages of 1/2 Vcc on the LCD, not
50 mV pp.
This also could point towards LCD clock being too high.

If this all fails, perhaps your LCD is too big, and you need more biasing
current in the
voltage divider.

Remember that an LCD should always be driven with AC, never DC (well, voltage,
not current :-)

B rgds
Kris


-----Original Message-----
From: msp430@msp4... [mailto:msp430@msp4...] On Behalf Of Richard
Sent: Saturday, 25 March 2006 4:47 AM
To: msp430@msp4...
Subject: [msp430] Strange LCD Behavior

I am using the MSP430F42x with a static LCD.  Some units are failing
with many LCD segments coming partially on that should be off.  I have
tried replacing the micro and the LCD to no avail.  On the segments
that should be off I can see a pulse train of about 50mV PTP.
Perhaps there is a problem in the PCB, I can find none.  Failure rate
is about 5-10%.
I am wondering if anyone else has had this experience.

Thanks

Rich







.

 
Yahoo! Groups Links



 




.

 
Yahoo! Groups Links