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Problem with 74165

 
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Skirmitt



Joined: 19 May 2009
Posts: 60

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Problem with 74165
PostPosted: Tue Jan 17, 2012 8:15 am     Reply with quote
I'm doing a project (midi controller) that has 74165's in it. The code is supposed to send a code when a button states changes at the inputs of the 74165's.

Code:

int16 data=0;
int16 olddata=0;
int i=0;

int buttarr[];
int oldbuttarr[];


read_expanded_inputs (&data);
if(olddata != data)
{

for(i=0;i<=15;i++){
      buttarr[i] = bit_test (data,i);
     
      if(buttarr[i] != oldbuttarr[i]) midiout(144,i,buttarr[i]);
     
      oldbuttarr[i] = buttarr[i];
     
}
}
olddata = data;


74165 are well defined and wired correctly. I have 2 of them.

Problem is that it gives a state change in the code when there is none. Could there be something wrong with a bit mask ?

State change on one port:

Code:
 TIMESTAMP IN PORT STATUS DATA1 DATA2 CHAN NOTE EVENT               
   2100793  1  --    144     7     0    1  G -1 Note Off             
   2100794  1  --    144    11     1    1  B -1 Note On               
   2100795  1  --    144    12     1    1  C  0 Note On               
   2100796  1  --    144    13     1    1  C# 0 Note On               
   2100797  1  --    144    14     1    1  D  0 Note On               
   2100798  1  --    144    15     1    1  Eb 0 Note On               
   2101341  1  --    144     6     1    1  F#-1 Note On               
   2101342  1  --    144    11     1    1  B -1 Note On               
   2101343  1  --    144    12     1    1  C  0 Note On               
   2101344  1  --    144    13     1    1  C# 0 Note On               
   2101345  1  --    144    14     1    1  D  0 Note On               
   2101346  1  --    144    15     1    1  Eb 0 Note On               
Mike Walne



Joined: 19 Feb 2004
Posts: 1785
Location: Boston Spa UK

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74165 circuit
PostPosted: Tue Jan 17, 2012 9:10 am     Reply with quote
You've not given me enough information.

I know it may seem silly but, can you provide a schematic of your 74165 arrangement, an indication of cable lengths to the 74165's, and just enough compilable code to reproduce the problem.

[I'm assuming you've got plenty of ceramic caps across supply rails.]

Mike
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