Variable expansion with i/o ports?

[eTech]

Is there a way to use variable expansion (in PIC Basic) with i/o ports?

In other words, is there a way to do something like this:

Dim a as byte

a = 1

If PORTB.(a) = 1 then
'do something
Endif

eT

 

[ronsimpson]

I think it will work. I have not used pic basic recently. The answer probably is on the PIC Basic forum. Do you get an error when you try it?

 

[eTech]

I think it will work. I have not used pic basic recently. The answer probably is on the PIC Basic forum. Do you get an error when you try it?

yes.

Error:
"There has to be at least one variable in the test expression"

I'm trying to write a procedure I can pass a value to flash an LED. The variable represents the port number.

So now i'm trying this approach:

Symbol led_1 = PORTC.1

Call flash_led(led_1)

Proc flash_led(ledno As Bit)
If ledno = 0 Then
High ledno
WaitUs 100
Low ledno
WaitUs 100
Else
Low ledno
WaitUs 100
High ledno
WaitUs 100
Endif
End Proc

 

[Mike_2545]

You need to :
Include "bs2defs.bas"

 

[eTech]

You need to :
Include "bs2defs.bas"

Will this work with the Oshonsoft Basic?

 

[Mike_2545]

Pic Basic Pro

 

[eTech]

Pic Basic Pro

OK..I guess Oshonsoft Basic isn't as flexible as other versions.

I can't do this:

Dim i As Byte
For i = 0 To 7 'loop for 8 counts
PORTB = %00000000 'make all pins low
PORTB.0 = 1 'make pin number i high <----compiler errors "Constant Arg cannot be used"
WaitMs 500 'pause for half a second
Next i

I need to be able to reference I/O pins with a variable.

Guess I'll look for a different compiler...

Thanks

eT

 

[ericgibbs]

hi,
This demo works on Oshonsoft

Dim i As Byte
Dim p As Byte

TRISB = 0x00

loop1:

PORTB.0 = 1
WaitMs 10''''''''''''''''''''added
For i = 0 To 7  'loop for 8 counts
PORTB = ShiftLeft(PORTB, 1)
WaitMs 10
Next i

Goto loop1

 

[eTech]

hi,
This demo works on Oshonsoft

Dim i As Byte
Dim p As Byte

TRISB = 0x00

loop1:

PORTB.0 = 1
WaitMs 10''''''''''''''''''''added
For i = 0 To 7  'loop for 8 counts
PORTB = ShiftLeft(PORTB, 1)
WaitMs 10
Next i

Goto loop1

OK...I'm not making the connection...

I need to be able to reference an I/O pin using a variable as the pin identifier.

I was hoping to be able to do this:

If PORTB.(i) = 0 Then
High PORTB.(i)
Endif

Is there a way to this?

eT

 

[Ian Rogers]

You only need to write a simple procedure to manipulate a port..

I just wrote a function to change any pin without altering any others

main:
	PORTB = writeport(LATB, 3, 1)
	PORTC = writeport(LATC, 2, 0)
	PORTB = writeport(LATB, 6, 1)
	PORTC = writeport(LATC, 1, 0)
Goto main
End                                               

Function writeport(port As Byte, pin As Byte, condition As Byte) As Byte
Dim idx As Byte
Dim buf As Byte
	idx = LookUp(1, 2, 4, 8, 16, 32, 64, 128), pin  'POWER OF 2
	buf = port  'READ PORT ( LATCH )
	idx = Not idx  'INVERT ALL BUT PIN
	buf = buf And idx  'AND TO CLEAR BIT
	If condition = 0 Then  'IF PIN NEEDS CLEARING FIN HERE
			writeport = buf  'RETURN WITH ONLY THAT PIN CLEARED
			Exit
	Endif
	idx = Not idx  'OTHERWISE WE NEED TO
	buf = buf Or idx  'SET JUST THAT PIN
	writeport = buf ' ALL DONE
End Function