Calling MCP23016 pins

Newzed · 2004-11-02 17:32

I have an MCP23016 with a lot of lines working.· I need to monotor the state of just of of the pins.· Can I write

if GP0.7·= 128 then do something?

12 of the pins on the chip could be in any state but I am only concerned about the state of GP0.7

Sid

Chris Savage · 2004-11-02 17:44

Sid, if you're monitoring one bit, then it would be either a 1 or 0...

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Chris Savage

Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777

Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
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·

Jon Williams · 2004-11-02 18:10

You need to read the whole port, then check the bit in question. Something like this:

I2CIN SDA, slaveAddr, GP0, [noparse][[/noparse]temp]
IF (temp.BIT7) THEN
  ' do something
ENDIF

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Jon Williams
Applications Engineer, Parallax
Dallas Office

Newzed · 2004-11-02 19:17

I took the easy way out, Jon.· I wrote:

if GP0>=128 then dosomething.·

This statement is true only of GP0.7 is
high.· If it is NOT true, then GP0.7 must be low.

Sid

Jon Williams · 2004-11-02 22:12

You're right.· On the other hand, you could write "better" (my opinion -- please hold your flames) code by doing things like this:

flags   VAR  Byte
frGate  VAR  flags.BIT7
 
IsOpen  CON  1
 
...
 
  IF (frGate = IsOpen) THEN
    ' deal with open front gate
  ENDIF

To many this seems like a lot of work, but after 20 years of programming I can assure you that it saves the programmer time, and is immensely helpful when that same programmer wants to share his/her code with others.· It's also helpful when you change a circuit design as a couple changes in your definitions section is easier than hunting through a long listing for "magic numbers."

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Jon Williams
Applications Engineer, Parallax
Dallas Office

Calling MCP23016 pins

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