Using as many internal peripherals as possible.
Hi,
I wonder how small the code can it be if I use as many internal peripherals as I could (and I know).
The task is simple, alternately slowly flash LEDs on ports RA0 and RA1. If the supply
voltage goes below 3V lit up the LED on port RA2.
I used PIC12F1840 mcu. Used it's comparator, fixed voltage reference and Timer0.
The code compiles used 42 words.
Just for fun, I wonder if it is possible to program it more effectively?
Code:
#CONFIG
__config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG
DEFINE OSC 4
OSCCON = %01101010
TRISA = %010000 ; RA4 input, rest output
ANSELA = %0000 ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256
FVRCON = %10011000 ; Internal reference to 2048V
CM1CON0 = %10100110 ; comparator uotput to C1OUT, switch on LED if voltageis beloe ref 2,048V
CM1CON1 = %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V
LATA = %000010 ; init state of pin RA0 and RA1, LEDs connected to these port
n var byte : n=0 ; init n value to 0
Main:
if INTCON.2 = 1 then n=n+1 : INTCON.2 = 0 ; if TMR0 owerflow increment n by 1, then clear owerflow flag
if n=10 then LATA = LATA ^ %000011 : n=0 ; if n=10 then invert bit 1,0. Pins RA0 and RA1 alternately flash the LEDs
goto Main
Re: Using as many internal peripherals as possible.
Even better, only 33 words.
Code:
#CONFIG
__config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG
OSCCON = %00110010 ; Clock 250kHz
TRISA = %010000 ; RA4 input for battery measurement, rest output
ANSELA = %0000 ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256
FVRCON = %10011000 ; Internal reference to 2048mV
CM1CON0 = %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 = %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V
LATA = %000010 ; init state of pin RA0 and RA1, LEDs connected to these port
Main:
if INTCON.2 = 1 then LATA = LATA ^ %000011 : INTCON.2 = 0 ; if TMR0 owerflow flip LEDs, then clear owerflow flag
goto main
I think, reached the limit of optimization.
Re: Using as many internal peripherals as possible.
How about this?
Code:
Main:
n = n + INTCON.2
INTCON.2 = 0
IF n.3 THEN
LATA = LATA ^ %000011
n=0
ENDIF
goto Main
It won't produce exactly the same frequency as your example but it's 12% smaller (37 words). I suppose there's also the odd chance/risk of the TMR0 interrupt bit being set in between checking it and clearing it. You COULD also do away with the n=0 at the start with the drawback of the FIRST iteration taking longer depending on the start value of n. AND, possibly, get rid of the GOTO Main and let the PC freerun and start over from the top.
Adding DEFINE NO_CLRWDT 1 saves one or two words depending on which version.
Using TMR1, which is 16 bits with its 8:1 prescaler instead of counting overflows should achieve similar results
Code:
T1CON = %00110001
Main:
IF PIR1.0 THEN
PIR1.0 = 0
LATA = LATA ^ %000011
ENDIF
Goto Main
Combining these I got it down to 34 words but have not checked if it actually works.
/Henrik.
Re: Using as many internal peripherals as possible.
I tested your codes, both works. The second example with TMR1 I like the most because maintain 4MHz clock. And yes, it compiles only 34 words. Just one more word than mine when I manipulate the clock speed.
Nice.
Re: Using as many internal peripherals as possible.
In my minimalist mania, I tried using interrupts. On pin RA3 hooked up 10k pullup and pushbutton to ground. On pin RA5 LED. First I tried the On Interrupt statement from PBP not work at all. Then I tried DT Instant interrupts, which worked flawlessly but the code size was a little big.
Then I came up with this. Is it ok to use interrupts like this?
I welcome comments so that I can learn from them.
Code:
#CONFIG
__config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG
DEFINE INTHAND INT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010
TRISA = %011000 ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA = %0000 ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256
FVRCON = %10011000 ; Internal reference to 2048mV
CM1CON0 = %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 = %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V
LATA = %000001 ; init state of pin RA0 and RA1, LEDs connected to these pins
T1CON = %00110001 ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000 ; Enable GIE, PEIE, IOCIE
PIE1.0 = 1 ; Enable TMR1IE Owerflow interrupt
IOCAN.3 = 1 ; Enable RA3 negative edge OnChange interrupt
; ------------ With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
; pause 10000 ; some stuff here
goto main
; ------------ INT Handler Routine ---------------
asm
INT:
endasm
IF PIR1.0 THEN LATA = LATA ^ %000011 : PIR1.0 = 0 ; Flash the LEDs on RA0 and RA1 alternately
if IOCAF.3 then LATA = LATA ^ %100000 : IOCAF.3 = 0 ; Toggle LED on Pin RA5 if button on RA3 is pressed
@ RETFIE
It compiles only 58 words, and the main section is empty, ready for some other code.
Re: Using as many internal peripherals as possible.
Quote:
Is it ok to use interrupts like this?
no , you may appear to get away with inserting pbp statements in an ASM interrupt but it is a delusion.
pbp statements set many internal variables to enable complex statements to be evaluated , executing foreign statements from an isr will pollute this process. thats why dt-ints exists.
use asm code in asm interrupts like this
Code:
#CONFIG __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG
DEFINE INTHAND myINT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010
TRISA = %011000 ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA = %0000 ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256
FVRCON = %10011000 ; Internal reference to 2048mV
CM1CON0 = %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 = %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V
LATA = %000001 ; init state of pin RA0 and RA1, LEDs connected to these pins
T1CON = %00110001 ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000 ; Enable GIE, PEIE, IOCIE
PIE1.0 = 1 ; Enable TMR1IE Owerflow interrupt
IOCAN.3 = 1 ; Enable RA3 negative edge OnChange interrupt
; ------------ With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
; pause 10000 ; some stuff here
goto main
; ------------ INT Handler Routine ---------------
asm
myINT
movlw 0
banksel PIR1
btfsc PIR1,0
movlw 3
bcf PIR1,0
banksel IOCAF
btfsc IOCAF,3
iorlw 32
bcf IOCAF,3
banksel LATA
xorwf LATA,f
RETFIE
endasm
Re: Using as many internal peripherals as possible.
Thanks Richard for the answer. I understand. In more complex cases, this could cause problems.
In my case, it works, but it is not correct to combine it like this.
So in PBP use only On Interrupt statement or DT Interrupts. Or only ASM interrupts.
Alternatively, a system variable can be set up, e.g.:
Code:
Test VAR BIT SYSTEM
and use it from PBP and ASM?
If I want to set the Test in PBP
Code:
Test = 1
or
@ bsf Test
If I want to set the Test in ASM
and use the variable from both PBP and ASM. Or it's not possible that way either.
Re: Using as many internal peripherals as possible.
Test VAR BIT SYSTEM
Will create a var in this case called PB01
and then define test as bit 0 in that var
#define Test PB01, 000h
@ bsf Test
translates to
@ BSF PB01 , 0 ;set test to a logic 1
bit vars and declaring them to be system located in no way makes their use asm interrupt safe if used with pbp statements in said isr
its the pbp statements not the vars where the issue lies
Re: Using as many internal peripherals as possible.
What I trying. Omit PBP code from ASM interrupt routine.
But this try not work, of course.
Where is the problem?
Code:
#CONFIG
__config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG
DEFINE INTHAND INT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010
TRISA = %011000 ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA = %0000 ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256
FVRCON = %10011000 ; Internal reference to 2048mV
CM1CON0 = %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 = %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V
LATA = %000001 ; init state of pin RA0 and RA1, LEDs connected to these pins
T1CON = %00110001 ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000 ; Enable GIE, PEIE, IOCIE
PIE1.0 = 1 ; Enable TMR1IE Owerflow interrupt
IOCAN.3 = 1 ; Enable RA3 negative edge OnChange interrupt
Switch var bit SYSTEM : switch = 0
; ------------ With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
if porta.3=0 and switch=1 then
LATA = LATA ^ %100000
pressed:
pause 20
if porta.3=0 then pressed ; if the button is still pressed loop and wait for release
Switch=0
endif
goto main
asm
INT
banksel IOCAF
btfsc IOCAF,3
bsf Switch ; set bit in Switch to 1
bcf IOCAF,3
RETFIE
endasm
Re: Using as many internal peripherals as possible.
Code:
bsf Switch ; set bit in Switch to 1
Among other things...
- that's not the form of an asm 'bsf' instruction
- you may have issues with the proper bank being selected... you are specifying 'banksel IOCAF', but where is 'Switch' located?
When writing asm it will do exactly what you specify... correct or not.
Re: Using as many internal peripherals as possible.
Quote:
Where is the problem?
Good luck trying to get pbp to set a bit var where you need it be
use a byte and place it in access space if you have to
enabling the timer1 interrupt and not servicing it will not work well
Code:
#CONFIG __config _CONFIG1, _FOSC_INTOSC & _WDTE_OFF & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_ON & _FCMEN_ON
__config _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_ON & _BORV_19 & _LVP_OFF
#ENDCONFIG
DEFINE INTHAND INT
DEFINE NO_CLRWDT 1
DEFINE OSC 4
OSCCON = %01101010
TRISA = %011000 ; RA4 input for battery measurement, RA3 input on change, rest output
ANSELA = 0 ; ADC Disable
OPTION_REG = %10000111 ; Disable internal pull-ups, TMR0 On, prescaller to 256
FVRCON = %10011000 ; Internal reference to 2048mV
CM1CON0 = %10100110 ; Comparator output to C1OUT, switch on LED if voltage is below ref. 2,048V
CM1CON1 = %00100001 ; C1IN1- pin is RA4, comparator voltage input, C1IN1+ positive input to FVR set to 2,048V
LATA = %000001 ; init state of pin RA0 and RA1, LEDs connected to these pins
T1CON = %00110001 ; TMR1 On, prescaller 1:8, Fosc/4
INTCON = %11001000 ; Enable GIE, PEIE, IOCIE
PIE1.0 = 0 ; DISable TMR1IE OVerflow interrupt
IOCAN.3 = 1 ; Enable RA3 negative edge OnChange interrupt
Switch var BYTE $7f SYSTEM
Switch = 0
; ------------ With TMR1 and interrupt, oscilator 4MHz ---------------
Main:
if porta.3=0 and switch=1 then
LATA = LATA ^ %100000
pressed:
pause 20
if porta.3=0 then pressed ; if the button is still pressed loop and wait for release
Switch=0
endif
goto main
asm
INT
banksel IOCAF
btfsc IOCAF,3
bsf Switch,0 ; set bit0 in Switch to 1
bcf IOCAF,3
RETFIE
endasm
Re: Using as many internal peripherals as possible.
Thank you, Richard, for the explanation.
Now I have a clearer understanding of how to work with variables and share them in ASM and PBP.
Active TMR1, yes. I just forgot to comment on this line.
Whenever I have the time, I try to learn something new about programming in PBP.
Right now, I'm experimenting with interrupts.
Advice like this is helpful in my efforts.
Louis
