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# Clashlab

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1. ## Interfacing To Power Lines

Well, what I wanna do is control a triac for light dimming. So I need to know when the power line crosses zero. I don't need a very high accuracy, 100 µs delay will be ok. But I don't want the interrupt to occur at the peak value of the sine curve nor the interrupt occurring at very different times if the sine curve is going down or up. So using a transformer to get a 9v sine curve is not acceptable because (50Hz) : Going from 0 to 1 needs 2v (TTL) => t = arcsin( 2 / 9 )/( 2 * pi * 50 ) = 0.7 ms later Going from 1 to 0 needs 0.8v (TTL) => t = arcsin( 2 / 9 )/( 2 * pi * 50 ) = 0.3 ms earlier This leads to a 1 ms different between two interrupts, on a 50Hz signal that is 10%, it's too much.
2. ## Interfacing To Power Lines

They did answer me: So I will not use that method. Instead I will connect the power line thru a resistor to a NOT gate (which allows exceeding the voltage specifications as long as the current specification is meet, i.e. SN74AHC1G04) and connect that output to the pic (also thru a resistor).
3. ## Interfacing To Power Lines

Hi, I would like to know if I can use the method described in AN521 to detect the power line zero crossing (that is using only a resistor) on a 16F88 using portB pin 7. I don't see the diodes on the datasheet schematic for that pin so I am wondering if I have to put them outside the pic. The reason I choose portB pin 7 is because I need an interrupt on change. Thanks
4. ## Problems Reading Porta In Interrupt

Ok, I will try this! I should have read the datasheet more deeply. Thanks a lot!
5. ## Problems Reading Porta In Interrupt

Hi, The way I connected the led to the pic is very simple: PIC (5v) ---- Resistor (470 Ohm) ---- Led ---- 0v I tried several other value for the resistor, form 47 Ohm to 2.7 kOhm but that doesn't change anything. I think your right about the origin of my problem, it explain the two situation I encountered. I also found that RA4 on a 16f88 is a schmitt trigger, but using RA3 (TTL) doesn't help. So how can I make sure that when I put a 1 on the led output I read a 1 after?
6. ## Problems Reading Porta In Interrupt

Hello, In am experiencing a wired problem trying to make a led blink. I what to use a timer (TMR0) to know when I need to change the led state. So I have a function that turns on the led and sets the timer. Then every 20 timer overflow I test the led state and change it. This is where I have a problem. When I am directly testing the led state, the led never blinks (it is like reading the led state always returns 0) so I need to use a variable to keep track of the led state. I really don't understand the problem and need your help to figure this out. Here are the files (led.h, led.c, main.c) I am using BoostC 6.84 lite license on a 16f88. You only need to provide power to the pic and tie a led (+ resistor) to porta bit4. I included a #define PROBLEM1: If you declare PROBLEM1, the led never blinks (which is wired). If it is not declared the led blinks (using a state variable). Trying to figure out what was wrong I found another problem : When using a variable to keep track of the led state (PROBLEM1 not defined) if I set another led (LED_RED, porta bit3) to 1 at each timer overflow it get wired again. I included a #define PROBLEM2: If you declare PROBLEM2, the LED_BLUE blinks but stays on for a short period of time and surprisingly LED_RED goes off for a very short time repetitively. If it is not declared the led blinks (well if PROBLEM1 is not defined ). I have included an archive containing the 3 source files and 3 hex files: led.hex: PROBLEM1 and PROBLEM2 NOT defined ==> LED_BLUE blinks ledProblem1.hex: only PROBLEM1 defined ==> LED_BLUE doesn't blink ledProblem2.hex: only PROBLEM2 defined ==> LED_BLUE stays on furtively LED_RED goes off furtively What have I done wrong? Thanks for your help. led.h #ifndef LED_H #define LED_H #define LED_BLUE porta.4 #define LED_RED porta.3 #define ON 1 #define OFF 0 #define TMR0_PRESCALER 6 #define LED_PRELOAD 100 /* CLOCK_FREQ = 8 MHz TMR0: Prescaler 1/128, preload: 100 => IT every 0.00998400 sec */ void ledInit ( void); void ledBlink ( unsigned char onDuration); void IT_led ( void); #endif /* LED_H */ led.c #include <system.h> #include "led.h" #define PROBLEM1 /*#define PROBLEM2*/ static unsigned char ledTimer = 0; static unsigned char blink = 0; #ifndef PROBLEM1 static bit ledState = 0; #endif void ledInit( void) { option_reg &= 0xC0; /* 0b11000000 We keep the 2 MBS unchanged */ option_reg |= TMR0_PRESCALER; } void ledBlink( unsigned char duration) { /* Save duration for use in IT_led */ blink = duration; /* Set the number of timer overflow */ ledTimer = blink; LED_BLUE = ON; #ifndef PROBLEM1 ledState = ON; #endif /* Load timer */ tmr0 = LED_PRELOAD; /* Allow timer IT*/ intcon.TMR0IF = 0; intcon.TMR0IE = 1; } void IT_led( void) { #ifdef PROBLEM2 LED_RED = ON; #endif /* If duration has elapsed */ if ( --ledTimer == 0 ) { /* Change led state */ #ifdef PROBLEM1 /* DOESN'T WORK : LED_BLUE STAYS ON */ if ( LED_BLUE == ON ) { LED_BLUE = OFF; } else { LED_BLUE = ON; } #else /* WORKS : LED_BLUE blink when using another variable to test the led state */ if ( ledState == ON ) { LED_BLUE = OFF; ledState = OFF; } else { LED_BLUE = ON; ledState = ON; } #endif /* Set the number of timer overflow */ ledTimer = blink; } /* Load timer */ tmr0 = LED_PRELOAD; } main.c #include <system.h> #include "led.h" #pragma DATA _CONFIG1, _WDT_OFF & _PWRTE_OFF & _INTRC_IO & _MCLR_OFF & _BODEN_OFF & _LVP_OFF & _CPD_OFF & _WRT_PROTECT_OFF & _DEBUG_OFF & _CCP1_RB0 & _CP_OFF; #pragma DATA _CONFIG2, _FCMEN_ON & _IESO_ON; static void init( void) { porta = 0; portb = 0; trisa = 0b00100100; trisb = 0b11000001; osccon = 0x72; } void interrupt(void) { if (intcon.TMR0IE == 1 && intcon.TMR0IF == 1) { IT_led(); intcon.TMR0IF = 0; } } void main( void) { /* General initialisation */ init(); /* Module initialisation */ ledInit(); intcon.GIE = 1; ledBlink( 20); for (;;); } BlinkLed.zip
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