Error in LONG variable addition?

[James Whyte]

I am using a HX711 Strain Gauge amplifier that has a 24 bit output, so I am using LONG variables and trying to do some averaging, but I have been having problems doing addition with LONG variables.

The plan is to take 4 x 24bit samples, add them, then divide by 4 to give a 4 sample average.
However the math does not come out right.
Rather than actual samples which will changed over time I have set my code to a constant for testing.
For example if I set;
HX711_DEC = 16735960
I get 02fd7b60 = 50166624 (x3), when it should be 66,943,840 (x4)

However if I set;
HX711_DEC = 11111111
I get 02a62b1c = 44444444 (x 4 = Correct)

What am I missing here?

`; ----- Configuration

#chip 16F877A, 4.00
#config OSC = XT, ;MCLRE_on, PWRT_ON

; ----- LCD connection settings

#define LCD_IO 8 'Sets up ports and pins to be used with LCD screen
#define LCD_RS PORTC.3
#define LCD_RW PORTC.4
#define LCD_Enable PORTC.5
#define LCD_DATA_PORT PORTD
#define LCD_Speed Meduim

dim HX711_RAW as long ;Raw Sample
dim HX711_AVG as long ;Cumulative average
dim HX711_DEC as long ;2's Complement converted to decimal

CLS
Locate 0,0
Print "START" 'Prints subroutine info on LCD
wait 1 s

MAIN:
Do forever
;HX711_DEC = 16735960
HX711_DEC = 11111111

'1st Sample
HX711_AVG = HX711_DEC
'2nd Sample
HX711_AVG = HX711_AVG + HX711_DEC
'3rd Sample
HX711_AVG = HX711_AVG + HX711_DEC
'4th Sample
HX711_AVG = HX711_AVG + HX711_DEC

CLS
Locate 0,0
;Print hex(HX711_DEC)
Print hex(HX711_AVG_E)
Locate 0,2
Print Hex(HX711_AVG_U)
Locate 0,4
Print hex(HX711_AVG_H)
Locate 0,6
Print hex(HX711_AVG)

wait 1 s

Loop`

[Anobium]

There is nothing wrong with you code. I get correct result here. I adpated your code to give me more debug but I get 66,943,840 (x4)

Post the the top line of your (program).asm file. It will look something like this.

;Program compiled by Great Cow BASIC (0.98.<<>> 2020-03-28 (Windows 32 bit))

My program:

#chip 16F877A, 4.00
#option Explicit
#config OSC = XT, ;MCLRE_on, PWRT_ON
; ----- LCD connection settings
#define LCD_IO 8 'Sets up ports and pins to be used with LCD screen
#define LCD_RS PORTC.3
#define LCD_RW PORTC.4
#define LCD_Enable PORTC.5
#define LCD_DATA_PORT PORTD
#define LCD_Speed Meduim
dim HX711_RAW as long ;Raw Sample
dim HX711_AVG as long ;Cumulative average
dim HX711_DEC as long ;2's Complement converted to decimal
CLS
Locate 0,0
Print "START" 'Prints subroutine info on LCD
wait 1 s
MAIN:
Do forever
HX711_DEC = 16735960
;HX711_DEC = 11111111
'1st Sample
HX711_AVG = HX711_DEC

'2nd Sample
HX711_AVG = HX711_AVG + HX711_DEC
'3rd Sample
HX711_AVG = HX711_AVG + HX711_DEC
'4th Sample
HX711_AVG = HX711_AVG + HX711_DEC

CLS
Print "Seed = d"
Print HX711_DEC
Locate 1,0
Print "AVG  = h"
Print hex(HX711_AVG_E)
Print Hex(HX711_AVG_U)
Print hex(HX711_AVG_H)
Print hex(HX711_AVG)

HX711_AVG = HX711_AVG/4

Locate 2,0
Print "AVG/4= h"
Print hex(HX711_AVG_E)
Print Hex(HX711_AVG_U)
Print hex(HX711_AVG_H)
Print hex(HX711_AVG)

Locate 3,0
Print "AVG/4= d"
Print HX711_AVG


wait 1 s
Loop

[James Whyte]

Yes, that was the problem.
Was: (0.98.00 2017-09-23)
Now: (0.98.06 2019-06-12 (Windows 32 bit))

I should have chcked that first.... well I did actually. The problem is the installer that I checked does not have the full version number. Even now the latest installer is GCB_Installer-98.exe and I thought I had updated, but must have not used the latest installer even hough I thought I had.

Anyhow, with latest version the problem does go away. Thanks for your help and keep up the good work.

Off topic: Is that some sort of virtual LCD screen capture you posted?

[Anobium]

Pleasure.

It is the Real Simulator. It is OK for simulation. But, @caroper is the real expert on Sims.