Faster DIG algorithm

[pedja089]

/My english isn't good. Tabsoft got it right.
I'll try to explain better...
I have word variable Pressure.
I need to extract digits from Pressure variable to 4 different variables for displaying on static 7 segment LCD.
Offtopic:
To dive LCD just connect pin to pin LCD with MCU, and in ISR XOR LAT with mask every 20mS or so...
BANKSEL PORTA 'Select Bank
MOVLW 11101111b 'Mask unused pins
XORWF LATA,F 'Invert unmasked pins and write to LATA
It should have lower power consumption than multiplexed LCD wit LCD module on PIC.

Back to topic:
One thing that I tried is to use DIG and 4 variable. If I can extract one digit much faster, then do same thing for all 4 digits. That is why I ask for faster extracting for one variable...
Other way is to use arraywrite, and DEC4 to extract digit. Each byte in array will have one digit.

Tabsoft, thank you. You give me an idea:
Pressure = 1234
tmpDig0 = Pressure // 10 'tmpDig0 =4
pressure = Pressure / 10 'Pressure=123
tmpDig1 = Pressure // 10 'tmpDig1=3
pressure = Pressure / 10 'Pressure=12
tmpDig2 = Pressure // 10 'tmpDig2=2
tmpDig3 = Pressure / 10 'tmpDig3=1
This will be probably ok. It takes just under 1,5mS.
I didn't mention that I'm using PBPL and running on intosc at 16MHZ for all test.
I'm waiting boards to arrive, so I can't measure current consumption jet. So there is always option to go back to PBPW.

Thank you all.

[Tabsoft]

I confirmed you observations when I reran the routines @ 16MHz and PBPL.

I did notice if you use PBP's "DIG" command, the number of instruction cycles used are not consistent for various 4 digit numbers.

Here is the data I collected.

Algorithm 1:
Pressure = 1234
'Start Stopwatch in MPLAB Simulator
tmpDig0 = Pressure dig 0
tmpDig1 = Pressure dig 1
tmpDig2 = Pressure dig 2
tmpDig3 = Pressure dig 3
'Stop Stopwatch in MPLAB Simulator

Algorithm 2:
Pressure = 1234
'Start Stopwatch in MPLAB Simulator
tmpDig0 = Pressure // 10
tmpDig1 = Pressure / 10
tmpDig2 = Pressure / 100
tmpDig3 = Pressure / 1000

tmpDig1 = tmpDig1 // 10 
tmpDig2 = tmpDig2 // 10
tmpDig3 = tmpDig3 // 10
'Stop Stopwatch in MPLAB Simulator

Algorithm 3:
Pressure = 1234
tmpDig0  = Pressure // 10 
pressure = Pressure / 10 
tmpDig1  = Pressure // 10
pressure = Pressure / 10
tmpDig2  = Pressure // 10
tmpDig3  = Pressure / 10
'Stop Stopwatch in MPLAB Simulator


PBPW @ 16MHz
Algorithm   Inst Cycles     Time
1           2958            739.50 us
2           2086            521.50 us
3           1783            445.75 us

PBPL @ 16MHz
Algorithm   Inst Cycles     Time
1           9626            2.406500 ms
2           6830            1.707500 ms
3           5839            1.459750 ms

Obviously PBPL slows down the routines considerably.

Good luck.

[pedja089]

Thanks.
I'll post current consumption when I get PCB.

[ruijc]

Hi guys,

This is an interesting topic.

I was wondering if the following line ( i dont know how fast it runs ) can also run faster with the technic shown above:

LCDOUT $FE,LINE2,"FREQ ",DEC DISPFREQ DIG 2,DEC DISPFREQ DIG 1,",",DEC DISPFREQ DIG 0, " KHz    "

Best regards
Rui

[Tabsoft]

Yes, it will reduce the number of instruction cycles in your example.
Given that you are only extracting 3 digits of your DISPFREQ variable, Algorithm #2 will be faster.

Assuming you are using PBPW not PBPL here are the instruction cycles results.

Using the DIG method: 7606 Inst Cycles
Using Algorithm #2: 7293 Inst Cycles

That is a savings of 313 instruction cycles. If you are running a 4Mhz Fosc/4 MCU then that would be a 313us savings.
Though it is a small savings on cycles and time, it does come at a cost of 3 extra byte variables to hold the values.

Here are the two code options tested.

tmpDig0 var byte
tmpDig1 var byte
tmpDig2 var byte
DISPFREQ var byte
LINE2 con $c0


DISPFREQ = 1234

'Start Stopwatch in MPLAB Simulator
LCDOUT $FE,LINE2,"FREQ ",DEC DISPFREQ DIG 2,DEC DISPFREQ DIG 1,",",DEC DISPFREQ DIG 0, " KHz    "
'Stop Stopwatch in MPLAB Simulator
'Output: FREQ 23,4 KHz

'Start Stopwatch in MPLAB Simulator
tmpDig0 = DISPFREQ // 10
tmpDig1 =DISPFREQ / 10
tmpDig1 = tmpDig1 // 10
tmpDig2 = DISPFREQ / 100
tmpDig2 = tmpDig2 // 10

LCDOUT $FE,LINE2,"FREQ ",DEC tmpDig2,DEC tmpDig1,",",DEC tmpDig0, " KHz    "
'Stop Stopwatch in MPLAB Simulator 
'Output: FREQ 23,4 KHz

[ruijc]

Greetings Tabsoft,

Thank you for the information and tip.
Very helpfull !

Regards
Rui