The 16f18877 has a Zero Cross Detector as one of its CIP.
I cannot find this component within FC.
Is the ZCD accessed by utilizing the "CODE" command icon within the flow chart?
Or am I missing something?
Did a search within FC and no results.
16f18877 internal Zero Cross Detector
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hippalator
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mnfisher
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Re: 16f18877 internal Zero Cross Detector
Yes, you would need to use some C to enable the ZCD module - this would be in either a code block or in a custom interrupt.
See section 21 of the datasheet.
It looks relatively straightforward - but if using it to measure mains zero crossing then great care is needed with the wiring (not something for a breadboard
)
The syntax REGISTERbits.FIELD = n (for example ZDCONbits.EN = 1) or REGISTER = n to set the whole register is used.
Martin
See section 21 of the datasheet.
It looks relatively straightforward - but if using it to measure mains zero crossing then great care is needed with the wiring (not something for a breadboard
)The syntax REGISTERbits.FIELD = n (for example ZDCONbits.EN = 1) or REGISTER = n to set the whole register is used.
Martin
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mnfisher
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Re: 16f18877 internal Zero Cross Detector
I wired up a PIC16F18877 to a signal generator and tried the ZCD hardware.
Note - I tested with a 20MHz external crystal - if you have use the internal oscillator at 32MHz you will need to set OSCCON. (I did a blinkie first to test settings correct!)
This very small sample code - I enable the ZCD interrupt handler (in the 'custom' interrupt enable block) setting INTN to enable negative edge interrupts.
The ISR toggles a pin - I used D1 (set in properties) - this is attached to a logic analyser.
I connected the signal to RA0 via a 10K resistor (and I set the signal to be -2.5 to +2.5V) (15K would probably be a better value for this?)
With a 50Hz signal - I get 20ms pulses at RD1.
Note that if I enable the INTP and INTN interrupts - the wave spends more time in one phase - though the total time is still 20ms. This is a result of the pic attempting to 'balance' the input to 0.75V (I guess) rather than 0V
A little testing and a 5kHz signal works AOK (but 10kHz does not!) Results at 32MHz will vary!
Martin
Note - I tested with a 20MHz external crystal - if you have use the internal oscillator at 32MHz you will need to set OSCCON. (I did a blinkie first to test settings correct!)
This very small sample code - I enable the ZCD interrupt handler (in the 'custom' interrupt enable block) setting INTN to enable negative edge interrupts.
The ISR toggles a pin - I used D1 (set in properties) - this is attached to a logic analyser.
I connected the signal to RA0 via a 10K resistor (and I set the signal to be -2.5 to +2.5V) (15K would probably be a better value for this?)
With a 50Hz signal - I get 20ms pulses at RD1.
Note that if I enable the INTP and INTN interrupts - the wave spends more time in one phase - though the total time is still 20ms. This is a result of the pic attempting to 'balance' the input to 0.75V (I guess) rather than 0V
A little testing and a 5kHz signal works AOK (but 10kHz does not!) Results at 32MHz will vary!
Martin
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- ZCD_Test.fcfx
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mnfisher
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Re: 16f18877 internal Zero Cross Detector
Something to try:
The ZCD should be capable of much higher speeds than this (although maybe not toggling a pin - which will take quite a few cycles) - try incrementing a counter in the ISR instead of the pin set - then output the count every 1s to a UART (via a FTDI convertor) or a display.
A capacitor between the signal and GND might also be a good idea (|wound the resistor lead around the MCU (in a ZIF socket) pin - which is not a good idea!)
Martin
The ZCD should be capable of much higher speeds than this (although maybe not toggling a pin - which will take quite a few cycles) - try incrementing a counter in the ISR instead of the pin set - then output the count every 1s to a UART (via a FTDI convertor) or a display.
A capacitor between the signal and GND might also be a good idea (|wound the resistor lead around the MCU (in a ZIF socket) pin - which is not a good idea!)
Martin