how to generate two signals from two ports at the same time by using p16f84

[bikxsici]

i am allowed to use pic16f84 and 10 mhz crystal. i think this project is impossible, since i have struggled so much, but unfortunately he has a circuit doing that with pic16f84 :0

[bikxsici]

thanks a lot mackrackit

that utility makes me more careful about timer. now let me review my program again

[cncmachineguy]

Your first post said you needed to be able to select 2 frequencies. How are they selected? If they are just hardcoded in and there is nothing in the "main", there is no need for an interrupt. You can do it all from the main routine. This will save all the time required to process the interrupt.your code would have 1 line looking for the timer overflow such as :

while !tmr0 overflow
wend

then load 2 counters, 1 for each output

freq1 = period / timer0
freq2 = period2 / timer0

then on each overflow, decrement the freq's. when 1 reaches zero

if !freq then
 toggle output bit
 reload freq
endif

now don't forget to reload the timer unless you can set it up to just free run. You will need to play with the freq's counter numbers to "tune" the output, but I suspect you can get it right on the money.

[bikxsici]

hi cncmachineguy

dividing two variables by tmr0 and obtaining two periods from tmr0, it seems to work, but i think there can be some problems. for example, should we reload tmr0 with respect to which signal? for the first pulses ok but then when next period start?

program below is what you said, isn't it? thank you for advices

    OPTION_REG=%00000000
    TMR0=0
    INTCON=%10100000
main:
    while   tmr0>=250 
    tmr0= 0
    wend
      
    freq1= per1 / timer0
    freq2= per2 / timer0
    
    if  freq1<1 then    
    toggle  a0
    per1=100
    else
    endif
    
    if  freq2<1 then    
    toggle  a0
    per2=200
    else
    endif
    goto    main

[bikxsici]

second one should a1 sory

[cncmachineguy]

You are close to what I mean. TMR0 Should be setup as a time base, you had mentioned 8uSec in another post. So compute the reload value for TMR0 such that you get an interrupt flag at 8uSec. (hint: use PicMultiCalc to help get the values)

Next the freq values are computed by YOU and hardcoded. so if TMR0 is 8uSec, and you need a period of 800 uSec, freq will be 800/8 or freq = 100.

Your while loop just needs to check for TMR0 interrupt flag bit. You do not want to enable interrupts, but the flag will be set anyway. So as soon as the flag is set you need to do this:

reload the TMR
clear the flag
decrement freq1 &freq2
check each for zero (IF !freq1 then) this will check if freq1 = 0

I will let you work on how to actually code the above. You almost have the Freq checks correct. Put comments in your code. This will do 2 things:
1 tells others and yourself what things are doing. If you code more beyond this class, you will be VERY happy you started doing this.
2 When you comment what you think things are doing, It will make it easier to see what is wrong. Here is a for instance:

while   tmr0>=250  ' this line checks if TMR0 is greater then 250
    tmr0= 0            'this line sets TMR0 to equal 0 if it is greater then 250
    wend               ' this is where the program jumps to when TMR0 is less then 250

This will not work ok, the ugly is all your program will run while waiting for the timer to reach 250. Then when tmr does reach 250, you just set it back to zero. Effectively tmr0 is doing nothing for you here. I will leave it to you to try to figure out why.

BTW, I am in no way a very good teacher, so please bear with me. My goal is to give you clues and help you to understand what is going on as opposed to telling you how to do each step. Is there a deadline when you must be done?

[bikxsici]

sory i am writing fast and i forget something. there is no deadline but i must submit as soon as possible.

i am going to review the program, and i will send the results , i must be careful. thanks a lot for your advices

best regards