HSerReceive in a Do..While loop

[Peter]

I have a GSM modem which communicates via serial.

To send an SMS I need to wait for a ">" prompt to appear.

This works

  Dim inChar as Byte
  Do
    HSerReceive inChar
  Loop While inChar <> 62

But this doesn't:

  Do
  Loop While HSerReceive <> 62

Is there a way to get the second version to work, just to keep the code neater?

I'm using 0.97.01.

[Anobium]

Post the section of errant ASM please. Let us look at what is happening.

[Peter]

I think this is the working ASM:

;Do
SysDoLoop_S1
;HSerReceive inChar
  pagesel HSERRECEIVE377
  call  HSERRECEIVE377
  pagesel $
  movf  SERDATA,W
  movwf INCHAR

;Loop While inChar <> 62 'Wait for > prompt
  movlw 62
  subwf INCHAR,W
  btfss STATUS, Z
  goto  SysDoLoop_S1
SysDoLoop_E1

And I think this is the one that doesn't work:

;Do
SysDoLoop_S1
;Loop While HSerReceive <> 62
  movlw 62
  subwf HSERRECEIVE,W
  btfss STATUS, Z
  goto  SysDoLoop_S1
SysDoLoop_E1

In the second case is it treating HSERRECEIVE as a variable and not a function?

[William Roth]

Hserreceiveive subroutine and not a function so the second method will not work.

Correction. It is both a sub and a function so it should work I think

But the the ASM does not show an HserReceive sub. Only the HserReceive Variable

With limited testing it appears that a function cannot be used as part of a conditional statement

This DOES NOT Work

waitforchar62:   
If hserreceive <> 62 then goto waitforChar62

The function is never called since there is no function or sub for hserreceive in the ASM

ASM

[mmotte]

Peter,
We have run into similar situation because of function overloading.

I tried William's example and as he says it don't call the HSerreceive function.

But if you change the hserreceive to hserreceive1 then it might work.

WAITFORCHAR62
;If hserreceive1 <> 62 then goto waitforChar62
    rcall   FN_HSERRECEIVE1
    movlw   62
    subwf   HSERRECEIVE1,W,BANKED
    btfss   STATUS, Z,ACCESS
    bra WAITFORCHAR62

Note now it does call FN_HSERRECEIVE1 and returns the value into the variable HSERRECEIVE1.

HSERRECEIVE1 is a valid function saying it is using com port number 1. it is in help file.

Calling hserreceive as a function don't really lessen your code because it calls the same subroutine and then puts it into a variable like your very first code.

BR
M

[Anobium]

@Mmotte is correct. This is caused by the compiler.

I thought I had written this up in the Help. But, I have failed you all.

Hugh will correct me....

These work;

  'Call the function by adding the braces 
  '
  Do
  Loop While HSerReceive() <> 62

  'Please the constant first - this is the general rule.  Always put the constant first.
  '
  Do
  Loop While 62 <> HSerReceive

This fails as the function will not be called

  Do
  Loop While HSerReceive <> 62

[Peter]

Both of those alternatives are neat enough for me.

[Anobium]

Please review this Help.. you will have to scroll to the bottom of the page....

What changes are needed to improve this Help page?

And, this is a constraint of the current compiler. This constraint is a low priority in terms of being removed.

[William Roth]

@Peter
While using the function may make neater looking GCB source code, it also uses 5 more words of program memory and takes longer to execute than using the sub with no function.