Beginner in need of help !!

[robbo78]

Thanks Tabsoft for that info & trying to help. I will go over all that until it becomes clear, I refuse to give up!

Thanks again,
Rob

[robbo78]

Okay I think I have made sense of this now - correct me if I'm wrong.

So if I wanted to set the comparator up with say an internal reference & output (cm<2:0> = 011), I would set the cmcon0 register as CMCON0 = %00000011 ?

Now to the VRR -

I think Im right in saying that the comparator uses the main VDD+ pin on the chip to compare the internal reference to? What I dont understand is this -

IF VRR=1 and VR3 ... VR0 = 1111 (15) with a VDD of 5V the Vref will be (15/24)*5 = 3,125V

^^ Where are they getting that 15 from? Also where do you get the 24 from?

IF VRR=0 and VR3 ... VR0 = 1111 (15) with a VDD of 5V the Vref will be 5/4+(15/32)*5 = 3,593V

^^ Also why has the 24 changed to a 32 just from vrr=1 changing to a 0?

One last question, Am I right in thinking that you have to use the CIN- pin on the chip to provide the voltage to check? Cant you use a comparator on any pin of the chip (apart from gp3, vdd & vss).

Thanks again,
Rob

[robbo78]

Update: Ive looked in the data sheet & found out the reason for dividing by either 24 or 32, if your working out low range then : 24, high range : 32. Thats another thing understood.

So the last thing I am struggling to understand now is, how do you get the number from th bits?

VR<3:0> = 1111 (15). < How on earth do you get 15 from just bits 1111?

This is the only thing that I'm struggling to understand now.

Thanks,
Rob

[richard]

the low range internal vref gives you 15 steps of 0.208 volt steps starting at 0v
the high range internal vref gives you 15 steps of 0.156 volt steps starting at 1.25v

if you don't need the cout as an actual physical output CM<2:0> = 110 is a better choice
and lets you chose pin 6 or 7 as your input (select with cmcon0.3 "CIS")
why waste pins on a 8 pin chip

0000=0
0001=1
0010=2
0011=3
...................etc etc
its called binary

[robbo78]

Edit: just re-read your post. I need to be able to read a pin & output on it at the same time (obviously with pauses, so do I need to use comparator with output?

Hi Richard, I just came back here from doing a bit of googleing. It took me about 2 mins to figure out that its just binary, maybe if I had paid more attention in Maths I would know this!

I now understand the voltage steps as well, everything is coming together now, its actually quite simple once understood.

I still need to know if you can use a comparator with internal reference on any pin or does it have to be the CIN- pin?

Cheers,
Rob

[richard]

if you don't need the cout as an actual physical output CM<2:0> = 110 is a better choice
and lets you chose pin 6 or 7 as your input (select with cmcon0.3 "CIS")

input to comparator is [ cin+ pin 7] or [cin- pin 6] with CM<2:0> = 110 its your choice

there are other modes but in all cases cin is only on pins 6,7

[richard]

if you need or can use the comparator output use CM<2:0> = 101
it still lets you chose pin 6 or 7 as your input (select with cmcon0.3 "CIS")

[robbo78]

Okay Richard thanks for your help.

So lets say I wanted an LED to be OFF if the voltage on cin+ is below 1.1v, & LED to be ON if the voltage is higher than 1.1v. Would I use this -

VR3 ... VR0 = 1000 (8) with a VDD of 3.3V the Vref will be (8/24) x 3.3 = 1.1V

I hope this is right lol

[richard]

there is not enough info to answer

what comparator mode ?
what cis setting
is vrr set
what cinv seting
how is led connected ?

[robbo78]

Richard, I'm specifically talking about just the VRR nothing else. I just want to know if I've got the workings out right. If you need the whole code to tell me if that part is right or not then I can do that no problem.

[richard]

that is correct it will set the reference to 1.1 for a vdd of 3.3v

[robbo78]

Thats great thanks for the help, now I can have a go at the code.

[robbo78]

Okay I have had a go & failed What am I doing wrong?

'PIC12f683

#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG

DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000010 'pin 6 analog
CMCON0 = %00000100 'comparator mode
VRCON = %00001000 'voltage reference
TRISIO = %00000010 'pin 6 input

POTEN VAR CMCON0.1 'pot pin 6
LED VAR GPIO.2 'led pin 5

PAUSE 20

main:
IF CMCON0.1 = 1 THEN
HIGH LED
ELSE
LOW LED
ENDIF
GOTO main

[Tabsoft]

Rob,

Glad to see your working through the design and issues.
You are very close.

Here are a couple of things you need to correct.
1. VRCON: Look at the register description in "Register 8-3" on page 53 of the datasheet.
In your program you are setting VRCON like this: VRCON = %00001000 'voltage reference
There are more bits in the register that you need to take into account.
A. You have bit7=0 which does this "0 = CVREF circuit powered down, no IDD drain and CVREF = VSS". This turns OFF the internal reference voltage.
You need to change this to "1", 1 = CVREF circuit powered on, to turn on the internal reference voltage circuit.
B. You have bit5 = 0 which does this "VRR: CVREF Range Selection bit 0=High Range"
This changes your CVref equation and result to this: "VRR = 0, CVREF = (VDD/4) + (VR3:VR0 X VDD/32)", which when you plug in your values you get this
for your reference voltage. (3.3/4) + (8/32) = (0.825) + (0.25) = 1.075 Vdc. Now this may be what you were actually trying to do, if so then your are good.

2. In your main loop you are attempting to test the output of the Comparator like this: "IF CMCON0.1 = 1 THEN"...
Look at the CMCON0 register description in "Register 8-1" on page 47 of the datasheet and compare that with the "CMCON0.1 = 1" above.
You are testing bit1 of the CMCON0 register, that is what the ".1" does. xxxx.1 says I want to look at bit1 of xxxx.
Is this the bit you need to check for the Comparator Output? If you're not sure have a look at "FIGURE 8-3" on page 49 and look at the figure for the
CM Mode you are using "100". That diagram indicates what the Comparator Output is by name.

Check and correct this.

3. Lastly, and somewhat obscure in the DS, you need to determine how you want the Comparator to test and output.
As I understand you want to check the input pin voltage against your "1.075 Vdc" reference you are setting up internally and have the following outcomes:
If the input is "Lower than 1.075 Vdc" you want the LED to be OFF and you want the LED to be "ON when the input is Higher than 1.075 Vdc".

To get these results you need to take a look at a couple of items in the datasheet.
A. Look at CMCON0, "Register 8-1" on page 47, and review the information for bit6 and bit4.
Also look at "TABLE 8-1" on page 48.
Between these two, you should be able to piece together how you need to configure the operation to get your desired "Output" of the Comparator.

You are getting close, hopefully these additional points will get you further on your way.

Regards,

[robbo78]

Hi Tabsoft, thanks a lot for your help I appreciate it. I will go back through everything you have stated & set it up right this time. I did think there were other bits to change but didnt want to mess as I didnt know what I was doing, but ai should now with your info.

Thanks again, I will let you know how it goes.
Rob

[Tabsoft]

Rob,

One correction in my earlier post.

The CVref calculation for High Range is CVREF = (VDD/4) + (VR3:VR0 X VDD/32).
Using your input values of VDD=3.3 and VR3:VR0=8, the calculation will come out like this.
(3.3/4) + (8 x (3.3/32) = (0.825) + (8 x 0.103125) = (0.825) + (0.825) = 1.65 Vdc

If you use Low Range then here is the info:
CVREF = (VR3:VR0/24) x VDD = (8/24) x 3.3 = 0.333 x 3.3 = 1.1 Vdc

Regards,

[robbo78]

Hi Tabsoft,

Right I have changed the bits in the VRCON to the right stuff, so I think that is right now. I did change bits in the CMCON0 but none of it seemed to make a difference, so I have put it back to how it was. I'm thinking either I'm testing the wrong bit still or my actual hardware setup is wrong.

Maybe you can point something out?

BTW I am using the low range Also this is correct - As I understand you want to check the input pin voltage against your "1.1" reference you are setting up internally and have the following outcomes: If the input is "Lower than 1.075 Vdc" you want the LED to be OFF and you want the LED to be "ON when the input is Higher than 1.075 Vdc".

Code -

'PIC 12F683


#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG


DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000010 'pin 6 analog
CMCON0 = %00000100 'comparator mode
VRCON = %10101000 'voltage reference
TRISIO = %00000010 'pin 6 input


POT1 VAR CMCON0.2 'pot pin 6
LED VAR GPIO.2 'led pin 5


PAUSE 20


main:
IF POT1 = 1 THEN 
HIGH LED
ELSE
LOW LED
ENDIF
GOTO main

Thanks again,
Rob

[Tabsoft]

Rob,

Yes you're not testing the correct bit for the actual output of the Comparator..

Look at my post again where I listed the things you need to correct. Look at item 2.
I point you to where you can find the answer of which bit in which register to test.
I also point you to where you can determine what the output of the comparator will be for different configurations and physical connections.

Have a read of this info again, I'm sure you'll get it.

Regards

[robbo78]

Hi Tabsoft, okay had another read at first it was just going over my head. Am I right in saying I need to read bit 6 of CMCON0? So CMCON0.6?

Thanks,
Rob

[Tabsoft]

Exactly!

CMCON0 Register:
bit 6 COUT: Comparator Output bit.
This is the logic bit output of the Comparator.

CM: Comparator Mode = 100


With this setup the comparator is comparing VIN- (CIN-/GP1) to VIN+ (which is not an external pin but it is "From CVREF Module", internal voltage reference)
So you need to look at the description of COUT in the CMCON0 register listed below AND you need to look at Table 8-1 in the DS.
This will help you work out what value CMCON0.6 will be based upon a given input on GP1.
Take note that CINV is a configuration bit within the CMCON0 register that determines the logic polarity of COUT.

COUT: Possible values
When CINV = 0:
1 = VIN+ > VIN-
0 = VIN+ < VIN

When CINV = 1:
1 = VIN+ < VIN-
0 = VIN+ > VIN

[robbo78]

Brilliant! Thanks for the info again your the best! I should be able to get this working how I want it to now, then & only then will I move onto interupt with it.

Thanks again,
Rob

[robbo78]

Hi Tabsoft, I got the comparator working perfectly so I decided to move onto adding an interrupt, which believe it or not hasn't worked. Here is the code I have fully written, maybe you can help where I have gone wrong?

Thanks,
Rob

You will probably have a laugh at this, as its probably completely wrong lol

'PIC 12F683

#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG

PAUSE 20 'wait for hardware to settle

DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000010 'pin 6 analog
CMCON0 = %00000100 'comparator mode
VRCON = %10101000 'voltage reference
TRISIO = %00000010 'pin 6 input

ON INTERRUPT GOTO SLSELECT 'interrupt handler is slselect
INTCON = %11001000 'enable GIE and GPIE; clear GPIF
IOC = %00000010 ' enable IOC1 (GPIO.1 Interrupt on change)
PIE1 = %00001000 'enable comparator interrupt

POT1 VAR CMCON0.6 'read potentiometer
LED VAR GPIO.2 'led pin 5

ENABLE
main:
HIGH LED 'light led
GOTO main 'repeat

DISABLE 'disable interrupts in handler
SLSELECT:
IF POT1 = 1 THEN 'if <1.1v sleep
NAP 1
ELSE
ENDIF

INTCON = %10001000  'enable GIE and GPIE; clear GPIF
PIR1 = %00000000 'reset CMIF
RESUME 'where left off
ENABLE 'enable interrupts

[Tabsoft]

Glad to hear if Rob.

You did not say what is happening only that it is not working.
I took a look at your code and several things jump out at me.

1. You are jumping into the deep end of the pool with testing "nap"
If would take a smaller step first. Set a flag in the ISR and resume. Then in the main act on the flag you set in the ISR.
This way you can see the effects of the ISR logic.
2. You have IOC.1 enabled, which is GP1, which you are using for the comparator. You need to comment out IOC.1.
3. You are not testing for which Interrupt is firing inside of your ISR. It is almost always a good practice to determine what interrupt caused the jump to the ISR.
4. At the end of your ISR you are not setting the INTCON register they way you think. I believe you have a typo in the value you are assigning to it.


I changed your code to the following which shows the changes.

'PIC 12F683

#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG

PAUSE 20 'wait for hardware to settle

DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000010 'pin 6 analog
CMCON0 = %00000100 'comparator mode
VRCON = %10101000 'voltage reference
TRISIO = %00000010 'pin 6 input

ON INTERRUPT GOTO SLSELECT 'interrupt handler is slselect
INTCON = %11001000 'enable GIE and GPIE; clear GPIF
'IOC = %00000010 ' enable IOC1 (GPIO.1 Interrupt on change)
PIE1 = %00001000 'enable comparator interrupt

POT1 VAR CMCON0.6 'read potentiometer
LED VAR GPIO.2 'led pin 5

bitTest var bit 'Debug test bit.  Set/Clear in ISR and Check in maiin

bitTest = 0

ENABLE
main:
    
    'HIGH LED 'light led
    LED = bitTest
    
GOTO main 'repeat

DISABLE 'disable interrupts in handler
SLSELECT:
    'IF POT1 = 1 THEN 'if <1.1v sleep
        'NAP 1
    'ELSE
    'ENDIF
    if PIR1.3 = 1 then  'Comparator Interrupt fired (must be cleared before resume)
        bitTest = POT1
    endif

    'INTCON = %10001000  'enable GIE and GPIE; clear GPIF
    INTCON =%11001000 
    PIR1 = %00000000 'reset CMIF
    RESUME 'where left off
    ENABLE 'enable interrupts

See if this gets you along further.

[robbo78]

Hi Tabsoft, okay thanks for all that. I will go back to flagging. I think I was
Getting a bit ahead of myself lol.

Let you know how it goes

[robbo78]

Hi, okay I've been playing about with comparator interrupt now & think I have got the hang of it using flags. The code below is something little I came up with

Now I think I would like to implement the nap command now, or do you think I should learn something else before jumping to the nap command?

Thanks again,
Rob

'PIC 12F683

#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG

PAUSE 50 'wait for hardware to settle

DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000010 'pin 6 analog
CMCON0 = %00000100 'comparator mode
VRCON = %10101000 'voltage reference
TRISIO = %00000010 'pin 6 input

ON INTERRUPT GOTO int1 'interrupt handler is int1
INTCON = %11001000 'enable GIE and GPIE; clear GPIF
PIE1 = %00001000 'enable comparator interrupt

POT1 VAR CMCON0.6 'read potentiometer
LED VAR GPIO.2 'led pin 5
loop1 var word 'loop1 counter

bitTest var bit 'Debug test bit.  Set/Clear in ISR and Check in main

bitTest = 0
Loop1 = 0

ENABLE
main:

IF bittest = 1 THEN 
GOTO FLASH
ENDIF
    
LOW LED

GOTO main


ENABLE
FLASH:



do
for loop1 = 1 to 1000
HIGH LED
PAUSE 1

NEXT LOOP1

for loop1 = 1 to 1000
LOW LED
PAUSE 1

NEXT LOOP1

IF bittest = 0 THEN
GOTO main
ENDIF

LOOP
  
    
DISABLE 'disable interrupts in handler
int1:
    
if PIR1.3 = 1 then  'Comparator Interrupt fired (must be cleared before resume)
BITtest = pot1
ENDIF 

INTCON =%11001000 
PIR1 = %00000000 'reset CMIF
RESUME 'where left off
ENABLE 'enable interrupts

[Tabsoft]

Rob,

Looks like you got it working.

One little thing though.
The Pause command is based upon the "DEFINE OSC" value to calculate the pause interval correctly.
It is a good practice to have your "DEFINE OSC" statement up top in the source code before you use any time sensitive commands such as "Pause x".

The way you have your program setup the following occurs, which I presume you have seen in practice on your physical system.
The LED on GP2(pin5) will stay LOW (OFF) while the voltage input on GP1(pin6) is above your reference voltage.
The LED GP2(pin5) will blink in 1sec intervals while the voltage input on GP1(pin6) is below your reference voltage.

This works fine on my simulator.

Good job!

It looks like you're ready for a "nap" now.

[robbo78]

Hi Tabsoft, thanks for comfirming also thanks again for all your help, I wouldnt have got to this point if it wasnt for you. I havent got a simulator so I just test straight on the BB.

I will drop the pause below the osc value, thanks for that tip

Do I implement the nap command in the same way as flashing an LED? So if bittest = 1 : nap 1, if bittest = 0 : goto main? Something like that ?

Thanks again,
Rob

[Tabsoft]

Rob,

Why don't you check this out.

'PIC 12F683

#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG


DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000010 'pin 6 analog
CMCON0 = %00000100 'comparator mode
VRCON = %10101000 'voltage reference
TRISIO = %00000010 'pin 6 input

PAUSE 50 'wait for hardware to settle

ON INTERRUPT GOTO int1 'interrupt handler is int1
INTCON = %11001000 'enable GIE and GPIE; clear GPIF
PIE1 = %00001000 'enable comparator interrupt

POT1 VAR CMCON0.6 'read potentiometer
LED VAR GPIO.2 'led pin 5
loop1 var word 'loop1 counter

bitTest var bit 'Debug test bit.  Set/Clear in ISR and Check in main


high LED    'Start with LED ON
pause 500   'Pause .5 secs so you can see the LED turn on

bitTest = POT1  'Take initial reading of input voltage state
Loop1 = 0

ENABLE
main:

    IF bitTest = 1 THEN 'input voltage is < reference voltage  
        low LED
        nap 1
    else    'bitTest = 0 - input voltage is > reference voltage
        GOTO FLASH
    ENDIF
        
    GOTO main


ENABLE
FLASH:
    do
        for loop1 = 1 to 1000
            HIGH LED
            PAUSE 1
        NEXT LOOP1
        
        for loop1 = 1 to 1000
            LOW LED
            PAUSE 1
        NEXT LOOP1
        
        IF bitTest = 1 THEN
            GOTO main
        ENDIF
    
    LOOP
  
    
DISABLE 'disable interrupts in handler
int1:
    
if PIR1.3 = 1 then  'Comparator Interrupt fired (must be cleared before resume)
bitTest = pot1
ENDIF 

INTCON =%11001000 
PIR1 = %00000000 'reset CMIF
RESUME 'where left off
ENABLE 'enable interrupts

[HenrikOlsson]

I will drop the pause below the osc value, thanks for that tip

Like Tabsoft wrote, you generally want your DEFINEs at the top of the program but it's for readabillity. In reallity it makes no difference because they are not runtime commands.

Another little note

        for loop1 = 1 to 1000
            HIGH LED
            PAUSE 1
        NEXT LOOP1

What's the purpose of setting the LED high inside the loop?
There's nothing inherently wrong in doing it but it does take (a little) bit of time.

Also, now that you're starting to get the hang of it you might want to consider ditching the HIGH/LOW commands and simply set the pin directly, LED=1, LED=0. For this to work you need to clear the corresponding TRIS-bit first (TRISO.2 = 0 ' Set GPIO.2 to output). Doing it this way executes faster and consumes less codespace since it doesn't waste resources clearing the TRIS bit each and every time (which is what HIGH/LOW does for you).

Again, you're not doing anything "wrong" - it all works fine, I'm just pointing out a couple of things you could improve and take with you to the next project.

/Henrik.

[robbo78]

Thanks guys, I will have a play

Rob

[robbo78]

Hi guys, okay I've been having a mess today & I am quite happy with myself. I managed to use the comparator successfully, now I have added a button into the routine.

It is all doing what I want it to but I am having this big issue with de-bouncing how do I sort this out, what is the best way? Do I need to read the button in a different way?

Here is the code -

'PIC 12F683

#CONFIG 
   __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF
#ENDCONFIG


DEFINE OSC 4 '4mhz ocsillator
ANSEL = %00000001 'pin 7 analog
CMCON0 = %00011110 'comparator mode
VRCON = %10100000 'voltage reference
TRISIO = %00101111 'pin 2,4,5,6,7 input

PAUSE 50 'wait for hardware to settle

ON INTERRUPT GOTO int1 'interrupt handler is int1
INTCON = %11001000 'enable GIE and GPIE; clear GPIF
PIE1 = %00001000 'enable comparator interrupt
IOC = %00001000 'pin 3 ioc

RTPOT VAR CMCON0.6 'right trigger pot
RTBITTEST var bit 'trigger debug test bit. Set/Clear in ISR and Check in main

BUT VAR GPIO.3 'tactile button
BUTBITTEST VAR BIT 'button test bit


RTBITTEST = RTPOT 'initial reading

BUTBITTEST = 0 'read 0 to start


ENABLE
main:

IF RTBITTEST = 1 THEN
GOTO RAPID
ENDIF

IF RTBITTEST = 0 THEN
GOTO SLEEPY
ENDIF

GOTO main


ENABLE
RAPID:

LOW GPIO.0 
PAUSE 70
TRISIO.0 = 1 
PAUSE 70

IF RTBITTEST = 0 THEN
GOTO SLEEPY
ENDIF

IF BUTBITTEST = 1 THEN
GOTO FLASH
ENDIF

GOTO RAPID


ENABLE
SLEEPY:

HIGH GPIO.5
PAUSE 1000
TRISIO.5 = 1
PAUSE 1000

IF RTBITTEST = 1 THEN
GOTO main
ENDIF

GOTO SLEEPY


ENABLE
FLASH:

HIGH GPIO.5
PAUSE 300
TRISIO.5 = 1
PAUSE 300

IF BUTBITTEST = 1 THEN
GOTO RAPID
ENDIF

GOTO FLASH

  
    
DISABLE 'disable interrupts in handler
int1:
    
if PIR1.3 = 1 then  'Comparator Interrupt fired (must be cleared before resume)
RTBITTEST = RTPOT
ENDIF

IF IOC.3 = 1 THEN
BUTBITTEST = BUT
ENDIF 

INTCON =%11001000 
PIR1 = %00000000 'reset CMIF
IOC = %00000000 'reset IOC.3
RESUME 'resume to where left off
ENABLE 'enable interrupts

[Tabsoft]

Rob,
You really don't state what the problem is, only that you see a problem.

A quick scan of the code leads to too many questions for me.
What are you trying to accomplish in the different subroutines Rapid, Sleepy and Flash?
You seem to be using two GPIO pins, one for Rapid (GPIO.0) and another (GPIO.5) for Sleepy and Flash.
Another question is why in each of the subroutines are you setting the GPIO high, pausing and then configuring the same GPIO as an input?

Without more info, it is futile to offer an opinion.