[visionegg] Re: parallel port 2nd

Have you tried grounding the pin (not just letting it float)? That may do the trick. I would try alternately grounding it and then giving it +5V and see if you can get the output to change.

Cheers!
Andrew

On Saturday, February 1, 2003, at 01:39 AM, Christoph Lehmann wrote:

Hi Andrew

I have some problems, which gets me crazy.....

with the code:


input_value = 0
while (input_value == 0):
my_debug_msg.append('before<' + str(input_value) + '>lastimage <'
+ str(last_image) + '>')
input_value = raw_lpt_module.inp(0x379) & 0x20 #I use pin 12
my_debug_msg.append('after<' + str(input_value) + '>lastimage <'
+ str(last_image) + '>')

and nothing(!) on the LPT (open port) gives me (cycling trough the whole
two times):

before<0>lastimage <0>
after<32>lastimage <0>
before<0>lastimage <1>
after<32>lastimage <1>

-> it seems that there is a logical 1 on the pin 12! why?

thank you very much, Andrew, for a hint

cheers
christoph


On Tue, 2002-12-17 at 18:07, Andrew Straw wrote:
Hi Christoph,

Your two questions about the parallel port are essentially the same.
"inp()" returns a byte (well, actually it's a Python int, but it will
always be 0-255).  When you've pointed it to the parallel port like
"inp(0x379)", 8 bits of the parallel port get stored in the return
value.  This happens according to the standard method for encoding
multi-pin digital signals.  In Python, this would be (obviously the
system drivers don't run Python...)

result = 0
for n in range(8):
     result += bit[n]*(2**n)

therefore to get bit[n], you want to do something like

for n in range(8):
     bit[n] = result & 2**n

So, if all you care about in your code is bit 4, you can just do bit4 =
result & 0x10. So, modify your code from
input_value = raw_lpt_module.inp(0x379) 

to
     input_value = raw_lpt_module.inp(0x379) & 0x10

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Christoph Lehmann
Department of Psychiatric Neurophysiology
University Hospital of Clinical Psychiatry
Waldau
CH-3000 Bern 60
Switzerland

Phone:  ++41 31 930 93 83
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