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I've got an Axiom 256 board I'm playing with and am having a
problem getting an interrupt to work on Port H the way I want it to. I've got a passive keypad hooked to it 4 pins configured as output and 4 as input. When a key is hit it ties one of the input and output pins together. If I used the polled method, turn on one output pin and then read it to see if any of the input pins are on, then it works fine. When I turn on the interrupt set all the output pins high and press a key, I get an interrupt as expected and when I read it I get the input pin high like I would expect, put when I turn around and poll it to see when output colunm is connected, I get nothing. Its like the output is turned off when you are in interrupt mode. I tried using polled mode when the interrupt flags are set and have no luck. Anyone have any experiance with this and know what my problem might be? |
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Port H interrupt on HCS12
Started by ●March 6, 2004
Reply by ●March 7, 20042004-03-07
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At 14:39 06/03/2004 +0000, you wrote: >I've got an Axiom 256 board I'm playing with and am having a problem >getting an interrupt to work on Port H the way I want it to. I've got >a passive keypad hooked to it 4 pins configured as output and 4 as >input. When a key is hit it ties one of the input and output pins >together. If I used the polled method, turn on one output pin and >then read it to see if any of the input pins are on, then it works >fine. When I turn on the interrupt set all the output pins high and >press a key, I get an interrupt as expected and when I read it I get >the input pin high like I would expect, put when I turn around and >poll it to see when output colunm is connected, I get nothing. Its >like the output is turned off when you are in interrupt mode. I tried >using polled mode when the interrupt flags are set and have no luck. >Anyone have any experiance with this and know what my problem might >be? Did you account for debouncing? Debouncing is an electrical phenomenon caused by mechanical switches. In this phenomenon the voltage will alternate between the two voltages (the old voltage and the new voltage) after pressing the keypad, which will last for some 1mSEC - 100mSEC before stabilizing on the new voltage. Maybe it is possible you are suffering from such debouncing. There are several ways to overcome the debouncing. The simplest one is to perform a delay in software to let the inputs stabilize before reading their state. Hope this helps, Doron Nohau Corporation HC12 In-Circuit Emulators www.nohau.com/emul12pc.html |
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Reply by ●March 9, 20042004-03-09
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I've got debounce logic in there, it works fine in polled mode. I can't seem to get the output configured pins to work when the interrupt is set even if it is only set on 4 of the pins. I'm writing a program to output to some LED's to test the theory. I may be stuck using polled mode when using a keypad, but that will complicate my code and screw up my timing. Dean --- In , Doron Fael <doronf@n...> wrote: > At 14:39 06/03/2004 +0000, you wrote: > >I've got an Axiom 256 board I'm playing with and am having a problem > >getting an interrupt to work on Port H the way I want it to. I've got > >a passive keypad hooked to it 4 pins configured as output and 4 as > >input. When a key is hit it ties one of the input and output pins > >together. If I used the polled method, turn on one output pin and > >then read it to see if any of the input pins are on, then it works > >fine. When I turn on the interrupt set all the output pins high and > >press a key, I get an interrupt as expected and when I read it I get > >the input pin high like I would expect, put when I turn around and > >poll it to see when output colunm is connected, I get nothing. Its > >like the output is turned off when you are in interrupt mode. I tried > >using polled mode when the interrupt flags are set and have no luck. > >Anyone have any experiance with this and know what my problem might > >be? > > Did you account for debouncing? > > Debouncing is an electrical phenomenon caused by mechanical switches. In > this phenomenon the voltage will alternate between the two voltages (the > old voltage and the new voltage) after pressing the keypad, which will last > for some 1mSEC - 100mSEC before stabilizing on the new voltage. > > Maybe it is possible you are suffering from such debouncing. There are > several ways to overcome the debouncing. The simplest one is to perform a > delay in software to let the inputs stabilize before reading their state. > > Hope this helps, > Doron > Nohau Corporation > HC12 In-Circuit Emulators > www.nohau.com/emul12pc.html > |
