Shortening redundant code

Brian Carpenter · 2006-02-01 05:03

Hey guys.· I am going to be using the I2C command set alot for this project that i am working on.· Here is a snippet of what i wrote

' -------------------------------------------------------------------------
' Subroutine Code
' -------------------------------------------------------------------------
FontSequence0:
 I2CStart SDA   'Display First set of sequence
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $00
 I2CSend  SDA, $01
 I2CSend  SDA, $00
 I2Csend  SDA, $01
 I2CStop  SDA
Pause ScrollSpeed
 I2CStart SDA   'Display Second set of sequence
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $01
 I2CSend  SDA, $00
 I2CSend  SDA, $01
 I2Csend  SDA, $00
 I2CStop  SDA
Pause ScrollSpeed
Return
 
FontSequence1:
 I2CStart SDA   
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $02
 I2CSend  SDA, $03
 I2CSend  SDA, $04
 I2Csend  SDA, $05
 I2CStop  SDA
Pause ScrollSpeed
 I2CStart SDA   
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $03
 I2CSend  SDA, $04
 I2CSend  SDA, $05
 I2Csend  SDA, $02
 I2CStop  SDA
Pause ScrollSpeed
 I2CStart SDA   'Display Second set of sequence
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $04
 I2CSend  SDA, $05
 I2CSend  SDA, $02
 I2Csend  SDA, $03
 I2CStop  SDA
Pause ScrollSpeed
 I2CStart SDA   'Display Second set of sequence
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $05
 I2CSend  SDA, $02
 I2CSend  SDA, $03
 I2Csend  SDA, $04
 I2CStop  SDA
Pause ScrollSpeed
Return

FontSequence2:
 I2CStart SDA   
 I2CSend  SDA, TopSlaveID
 I2CSend  SDA, $60
 I2CSend  SDA, $20
 I2CSend  SDA, $0A
 I2CSend  SDA, $06
 I2Csend  SDA, $20
 I2CStop  SDA

I know that i should be able use one SendIt command that would have all the I2C stuff in it and just send the variables to it.· I can write it like this

Wing Var Byte
M0 Var Byte
M1 Var Byte
M2 Var Byte
M3 Var Byte
SendIt:
 I2Cstart SDA
 I2CSend  SDA, Wing
 I2CSend  SDA, M0
 I2CSend  SDA, M1
 I2CSend  SDA, M2
 I2CSend  SDA, M3
 I2CStop  SDA

i cant understand how to send the data to the variables and to the SendIt subroutine

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It's Only A Stupid Question If You Have Not Googled It First!!

Jon Williams · 2006-02-01 05:21

Brian,

As you figured out, your code is redundant (always sending four bytes) so you could create a subroutine like this:

Update_Display:
· temp1 = __PARAM1
· temp2 = __PARAM2
· temp3 = __PARAM3
· temp4 = __PARAM4

· I2CSTART SDA
· I2CSEND SDA, TopSlave
· I2CSEND SDA, $60
··I2CSEND SDA,·temp1
··I2CSEND SDA,·temp2
··I2CSEND SDA,·temp3
··I2CSEND SDA,·temp4
· I2CSTOP
· RETURN

Of course, you'd have to define this at the top of the program like this:

Update_Display··· SUB·····4

... and then -- here's the cool part --·you can call it from your program like this:

· Update_Display $00, $01, $00, $01

This will be easier to code, and save a lot of space as you're·expanding·fewer I2CSEND instructions.

·

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Jon Williams
Applications Engineer, Parallax

Post Edited (Jon Williams (Parallax)) : 2/1/2006 8:41:41 PM GMT

Brian Carpenter · 2006-02-01 05:25

Hey Jon, Thanks for the answer. I will try to impliment this.
thanks, Brian

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It's Only A Stupid Question If You Have Not Googled It First!!

Jon Williams · 2006-02-01 05:32

Have a look at the examples in the help file; they'll give you the guidance you need.

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Jon Williams
Applications Engineer, Parallax

Brian Carpenter · 2006-02-01 05:44

Jon, You Wrote

I2Cstart SDA, TopSlave

Can the address to the i2c chip be on that line? It is not shown that way in the example

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It's Only A Stupid Question If You Have Not Googled It First!!

Jon Williams · 2006-02-01 07:29

No, it can't. Remeber that I2CSTART and I2CSTOP are specific manipulations of the SDA and SCL lines, so I2CSTART doesn't send anything -- you have to do that with I2CSEND.

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Jon Williams
Applications Engineer, Parallax

Paul Baker · 2006-02-01 15:09

And if you are looking for further code space reductions, you can wrap a function around the I2CSEND function itself so that the code for I2CSEND appears only once in your code listing.

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·1+1=10

Jon Williams · 2006-02-01 15:35

Paul's idea is a good one for all of the I2C-related commands, as each of them generates a bit of code to deal with I2C-specific timing requirements.· I've pulled routines I used in another program and dropped them into a shell for you to use.· You might need to massage things a bit based on your variable use, but this should get you very close.

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Jon Williams
Applications Engineer, Parallax

Post Edited (Jon Williams (Parallax)) : 2/1/2006 3:42:10 PM GMT

Bean · 2006-02-01 16:19

Brian,
I think what has you confused is that Jon wrote "I2CSTART SDA, TopSlave"

I believe he meant:
"I2CSTART SDA"
"I2CSEND TopSlaveID"

Bean.

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Jon Williams · 2006-02-01 20:42

Whoops... sorry about that, Brian, my fault (I shouldn't stay up so late). Thanks for the catch, Bean, I've fixed the offending post.

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Jon Williams
Applications Engineer, Parallax

Shortening redundant code

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