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Posted: **Fri Aug 01, 2008 3:42 pm**

Maybe I didn't found it, but is there a module in Flowcode that I can use to get a comparator working?
I have two PIC's that have this functionality but I don't seem to find a module in Flowcode for PIC's 3.4.7.48

What I want to do is offer a reference voltage to the comparator, and another voltage to the other pin.
Everytime the voltage is a certain amount higher or lower than the reference voltage, it should be counted.

Thanks

Posted: **Fri Aug 01, 2008 4:19 pm**

Sorry, but you will have to do this by inserting your own C code into your Flowcode program.

Posted: **Fri Aug 01, 2008 4:20 pm**

Hello

Currently there is no comparitor component for Flowcode. The main reason for this is the lack of interest in this peripheral. I think that this component will be available in Flowcode V4 when it is released. In the mean time you can use C code to directly control the comparitor module registers onboard the chip. You should even be able to set up a custom interrupt so that an interrupt is triggered each time the comparitor is equal or greater etc. There is a lot of information on the comparitor module in the device datasheet. There is also a lot of help with custom interrupts in the Flowcode V3 help file. If you get stuck or run into difficulties then let us know.

Posted: **Sat Aug 02, 2008 10:31 pm**

Flowcode is a great program for people like me that want to play with PIC's but don't like the code.
Times like these when I want to use the comparator brings me back on my feet.
PIC's are much complex than what you see using Flowcode.

I was looking at the datasheet for the 16F628A

Code: Select all

FLAG_REG EQU 0X20
CLRF FLAG_REG ;Init flag register
CLRF PORTA ;Init PORTA
MOVF CMCON, W ;Load comparator bits
ANDLW 0xC0 ;Mask comparator bits
IORWF FLAG_REG,F ;Store bits in flag register
MOVLW 0x03 ;Init comparator mode
MOVWF CMCON ;CM<2:0> = 011
BSF STATUS,RP0 ;Select Bank1
MOVLW 0x07 ;Initialize data direction
MOVWF TRISA ;Set RA<2:0> as inputs
;RA<4:3> as outputs
;TRISA<7:5> always read β€0β€™
BCF STATUS,RP0 ;Select Bank 0
CALL DELAY10 ;10ΞΌs delay
MOVF CMCON,F ;Read CMCON to end change
;condition
BCF PIR1,CMIF ;Clear pending interrupts
BSF STATUS,RP0 ;Select Bank 1
BSF PIE1,CMIE ;Enable comparator interrupts
BCF STATUS,RP0 ;Select Bank 0
BSF INTCON,PEIE ;Enable peripheral interrupts
BSF INTCON,GIE ;Global interrupt enable

What should I use from this code to make the comparator change a variable whenever the voltage on the input is <> than the reference voltage (Vref) on a pin?
Correct me if i'm wrong, but when I want to use "Two Common Reference Comparators" I need to use this: CM<2:0> = 011
This is the configuration for two comparators with a common input.

What I can make of this code is that it generates a byte with several possibilities.
CMCON is a register where the result of the comparator is being stored?
So if I can use the value of this register I can make decisions and use it as a variable?

Is it possible to alter the code above to use in Flowcode, so I can use it in my project?
An Flowcode example would be great to start me up. With a little explanation, this would be great for everyone that want to use this feature of PIC's...

Thanks!

Posted: **Mon Aug 04, 2008 10:14 am**

Hello

Here is how you do the above program with Flowcode.

1) C code block to initialise Capture / Compare:

Code: Select all

char temp;
porta = 0;
cmcon = 0x03;
trisa = 0x07;
delay_10us(1);
temp = cmcon;

2) Custom Interrupt to handle the comparison

Enable

Code: Select all

clear_bit(pir1,CMIF);
set_bit(pie1, CMIE);
set_bit(intcon, PEIE);
set_bit(intcon, GIE);

Disable

Code: Select all

clear_bit(pie1, CMIE);

Handler

Code: Select all

if (pir1 & (1 << CMIF))
{
FCM_%n(); // call selected macro
clear_bit(pir1, CMIF); // clear interrupt
}

You can then read back the comparitor values by using the following C code block and 2 variables named C1 and C2.

Code: Select all

FCV_C1 = test_bit(cmcon, C1OUT);
FCV_C2 = test_bit(cmcon, C2OUT);

Posted: **Mon Aug 04, 2008 2:04 pm**

Thank you very much!

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