Well I got the led working like I wanted by using a pulldown resister. Now I'm trying to learn how to use delay subs. Basicly I'm trying to have the led blink at one speed when GP1 = 0 and then at a different rate when GP1 = 1. Here is the code I have. I'm thinking the problem may be the i,j,k variables not being declared right? At this point the pic dosn't light the led (or the delay is realy realy long). Thanks in advance. PHP: list p=12F629 ; list directive to define processor #include <p12F629.inc> ; processor specific variable definitions __CONFIG _CP_OFF & _CPD_OFF & _BODEN_ON & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _INTRC_OSC_NOCLKOUT ;----VARIABLES HERE----- CBLOCK 0X20 ;PUT YOUR VARIABES HERE i j k ENDC ;----------------------- ORG 0X000 CALL INIT GOTO MAIN ORG 0X004 RETFIE INIT CLRF GPIO MOVLW B'00000111' ;TURN OFF COMPARATOR MOVWF CMCON BSF STATUS,RP0 MOVLW B'00000010' ;SET ALL PINS TO OUTPUT EXCEPT GPIO,1 MOVWF TRISIO BCF STATUS,RP0 RETURN MAIN BTFSS GPIO,1 ;GPIO,0 HIGH WHILE GPIO,1 INPUT IS HIGH MOVLW .2 BTFSC GPIO,1 MOVLW .50 BSF GPIO,0 CALL dly BCF GPIO,0 CALL dly GOTO MAIN dly: movwf i ; 1 - start Code that isnt mine dly1: clrf j ; 1 dly2: clrf k ; 1 dly3: decf k,F ; 1 btfss STATUS,Z ; 1/2 goto dly3 ; 2 decf j,F ; 1 btfss STATUS,Z ; 1/2 goto dly2 ; 2 decf i,F ; 1 btfss STATUS,Z ; 1/2 goto dly1 ; 2 return ; 2 END
cblock is fine, 1 letter variable names are bad, but in asm its perfectly okay practice Now, make ur code clearer, indent on things like ORG, or CBLOCK ie Code: ORG 0x00 CLRF INTCON same goes when you have control structures, ie, BTFSS or DECF, makes it easyer to read. so a simple re-write will be: PHP: dly: movwf i ; 1 - start Code that isnt mine dly1: clrf j ; 1 dly2: clrf k ; 1 dly3: DECFSZ k,F ; 2 goto dly3 ; 2 (1) remeber DECFSZ ALWAYS 2 cycles, it NOPs if it dosen't excecute, so count one of the GOTO ones there! DECFSZ j,F ; 2 goto dly2 ; 2 (1) DECFSZ i,F ; 2 goto dly1 ; 2 (1) return ; 2 END now dly3 = 2 * FF dly2 = ( 1 + dly3) * FF dly1 = ( 1 + dly2) * i say for .50, we get = (( 1 + ((1 + ( 2 *FF)) * FF)) * .50 so 6515300 cycles. which using intrc which has an instruction cycle of 1mhz is 6.5153 seconds.
well to find out how short this code could be, we must use the same equations as above, i (the input passed in W) is only taken into acount in one place, and its times 0, but as 0 can't be passed (decfsz= decrement file register, skip if = 0), as it gets decremented before been tested, 0 becomes -1 (0xFF). so you can only have as low as 1, so ((1+((1+(2*FF)*FF))* 1; 130306cycles, so 0.13036th of a second running of intrc.
Humm maby I just need to find out how to figure all the math up. The one thing I'm not sure about is how to figure out how many cycles I would need to waste at a set clock speed to = like 20us or some thing like that.
metric prefixes always get me, so i always keep them as 10 to the power x much easyer using standard form. now, a PIC takes 4 cycles to do fetch execute, so instruction clock = actual clock / 4 when intrc=4x10^6, that means the instruction clock is 1,000,000, that means one instruction takes 0.1x10^-6 (1us) so a clock thats a twenteth of the speed of 4mhz, will do great, 200khz would do this. But why not just make a simple delay function? theres nothing wrong with have Code: Delay17: GOTO $+1 GOTO $+1 GOTO $+1 GOTO $+1 GOTO $+1 GOTO $+1 GOTO $+1 NOP RETURN so doing CALL DELAY17 will waste 19 cycles, now if you've got the memory space in your 12f629, this is a great way of not needing an external clock source. This way you get a 20us speed by using call delay17 after every instruction, of course branch is harder Some PICs you can change the speed of intrc, i don't think the 629 you can, but check the datasheet. Whats it your doing?
At this point I'm still just learning about stuff with the 12f629. Figuring out timing, reading inputs, and learning the little bits of asm I wasn't sure about. This is what I have done with the 12f629 so far. 1. blink and led (simple enough once I figured out the TRSIO and GPIO registers) 2. turn the led on when I turn a switch on. This part was harder because I didn't use a pulldown resister in my original lay out so I was having issues with the pin floating. 3. blink the led at a rate based on the position of a switch. Next project I plan to give a go is moving a servo to two different locations based on the switch. After I learn that I may work on geting my 16f88 set up with the max232 that I have and do some basic serial stuff (probably make the pic echo what is sent down the serial port from the pc). In the end the project that I bought all of this and am learning this for is to interface some dallas 18b20 temp sensors (preferably 10-15 at max) and have the pic poll the 1-wire net and then report the temps back to my windows box.
ah ic, well the LED blinking with a 20us interval will be so tiny the human eye will just see it as been dimmer. its really easy with a RISC like this to think each instruction (running of intrc @ 4mhz) will take 1us, some instructions (jumps + branches) take 2 cycles, they always take two cycles, so its very easy to code with time in mind. if you make it so when the switch is pressed, the LED is on for 5us, then off for 100us, it will go quite dark, and you shouldn't see the flicker !
Ok so if I am geting this right 1us = 1/1000 of a second? If that is the case this wont be to hard to under stand.
Ok thanks I was thinking 1us was ula-second (which I must have made up in my mind). Ok just making sure I got this right 1us = 1 micro-second.
I know this is an old post, but I thought I should point out, that 1 micro-second (1us) = 1/1,000,000. and 1 milli second (ms) = 1/1,000. It's so easy to confuse them when your a beginner. I hope this will help the beginners.
