Forum: ARM programming with GCC/GNU tools About PIOA pull up Resistera

von Min G. (minge519)

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Hi All,

I have a question. I use PA27-30 as switches input. I connect my switch
to PORT pin via 1K ohm RES (For protection). When press switch, pull
port pin to low. I enabled AT91SAM7S64 Internal pull up RES (10K ohm
according to datasheet) and set pin as input. I found when I press
switch, the voltage on port pin is only 1.8V (I use 3.3V Power Supply).
and there is 1.8 voltage voltage accross the 1K Ohm RES. That confusing,
if the internal Pull upis 10K, the 1K Ohm RES should have only 1/10 *
3.3V, why is that so high.
Is there anybody run into this problem?


Min Ge


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