Lpc2000

*       We have an application where we use the GPIO I/O pins on Port 1 of
> LPC2138 to an LCV244 buffer/driver.  We found that randomly, some pins
> on the buffer driver were high or low at power-up with no program
> loaded to control the pins.  We added 32k pull downs between the 2138
> and the buffer/driver inputs to pull the lines low because the GPIO
> lines are floating inputs before program changes them into outputs.
> However, we are still randomly seeing some outputs on buffer/driver
> high and some low on power up.  We measured between 0.4 and 1.2 volts
> on those lines. Why are 32k pull downs not working for us ?

Remember that all P1.x pins have internal pull-ups of 60-300 kohm.

Karl Olsen

All,

I appreciate all who replied. Because we needed to ensure that all of our
outputs were held low through reset, we utilized the gate enable pins on the
LVC244 buffers to hold buffer output low through reset, then programmed an
output pin to drive gate enable pins low once our program is up and running.


 

Regards,

Nick

 

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