Displaying negative numbers

Newzed

I am trying to get my LCD to display negative numbers indicating the position of the X or Y drive on my MF70 mill.

I have the origin set at 0, 0.· If I stay to the right of 0, the display is correct.· I can move .400 left - display = .400 - then move right .100 and display = .300.· All OK so far.

However, if I am at origin and I move the table right .100, then the display says 65436 instead of -.100.

Position is calculated by 0 -· dis, where dis is the travel after a go right command execution, or by 0 + dis after a go left command execution.
I am using SDEC modifiers.

Any suggestions?

Sid

Jon Williams

As you frequently suggest, Sid, perhaps you should post your code. SDEC will work in the right context. You can also do it yourself: look at BIT15 of your value; if it's "1" then the value is negative so you display "-". After that you take the ABS[noparse][[/noparse]solute] value you're working with and display it.

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Jon Williams
Applications Engineer, Parallax

Newzed

The complete code for this program is huge so I'm reluctant to post the whole thing.· However, here afe snippets covering the matter under discussion.

This is the routine that calculates travel.· It is shown for just 360 degrees:

diffd = f
IF f = 360 THEN
dis = ABS diffd*/$0046 + 2
ENDIF

dis always = 1000

to display it on the LCD, I write:

SEROUT lcd, baud, 10, [noparse][[/noparse]"B", "Travel: ", SDEC dis/1000,".", DEC3 dis, " out", 13]

To calculate the total - or net - travel (disy) from origin - 0, 0 - I write:

disy = disy - dis

To display, I write:

SEROUT lcd, baud, 10, [noparse][[/noparse]"C", "Total travel: ", SDEC disy/1000,".",DEC3 disy, 13]

The LCD displays 65.436.

If I change the display instruction to:

SEROUT lcd, baud, 10, [noparse][[/noparse]"C", "Total travel: ", SDEC disy, 13]

the LCD displays -100.· I can put a dot in front of it and get .-100 but what I want the display to say is -.100.· I have no problems as long as disy is =>0.

Is this enough of the code?

Sid
·

Newzed

Small correction to the above post - dis = 100 not 1000.

Sid

Jon Williams

You cannot do division on negative numbers in PBASIC.· Update your code like this:

· temp = ABS dis
· SEROUT Lcd, Baud, 10, [noparse][[/noparse]"B", "Travel: ", " " + (dis.BIT15 * 13), temp/1000, ".", DEC3 temp, " out", CR]

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Jon Williams
Applications Engineer, Parallax