Electronic – burn a led with the switchs on pic 18F4550

microcontrollerpic

I'm using the pic 18F4550 with microchip v8.63 and with the C compiler C18.

I want to trigger port RB3, RB4 and RB5. when, I press on respectively S1 (switch 1), S2 switch (S2) and S3 (switch 3). on these ports (RB3, RB4 and RB5) there are leds connected to, the should burn when I press S1 or S2 or S2.

My first question is, How do I stream from my S1 and S2 and S3 to the gates (RB3, RB4, RB5).

And second how can I enable port RB6, there is a light dependent resistor connected to.

I wrote this program: but, nothing is happening. only led 1 goes on.

#include "p18cxxx.h"  
void main(void) 
{ 
    // turn off all LED latches 
    LATDbits.LATD0 = 0; 
    LATDbits.LATD1 = 0; 
    LATDbits.LATD2 = 0; 
    LATDbits.LATD3 = 0; 
    // make port d bits which drive LEDs outputs 
    TRISDbits.TRISD0 = 0; 
    TRISDbits.TRISD1 = 0; 
    TRISDbits.TRISD2 = 0; 
    TRISDbits.TRISD3 = 0; 

    if(PORTBbits.RB3 == 0) {
        LATDbits.LATD0 = 1;     
    }
    if(PORTBbits.RB4 == 0) {
        LATDbits.LATD1 = 1;
    }
    if(PORTBbits.RB5 == 0) {
        LATDbits.LATD2 = 1;
    }
}

Best Answer

Your main routine runs once only. You need a loop, probably starting after the ports are initiallised, around the if statements.

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If you connect another resistor to Vdd you can make a voltage divider, which has an output voltage determined by the two resistances. The ADC will give you the voltage, and some algebra will get you the resistance.
You could build a constant-current source, and pass this current through the LDR. Then the voltage across the LDR will be exactly proportional to the resistance.
You could use a capacitor from the LDR and connect it to another pin. When the capacitor pin is set high, you can watch the rise time on the capacitor-LDR connection. This technique does not require an ADC. (For more accuracy, charge the capacitor through a known resistance and discharge through the LDR, then use the charge time / discharge time ratio.)

Electronic – Enable port RA0 as input and retrieve value LDR from led

Firstly, lets check that you have connected your LDR up correctly, it should be something like this...

LDR wiring

To read the value of PIN RA0/AN0, you need to do some initialisation to make sure the port is setup correctly. The datasheet explains how all this works, but these values should work:

TRISAbits.TRISA0 = 1;           // Set RA0/AN0 to input
ADCON0           = 0b00000000;  // Set channel select to AN0
ADCON1           = 0b00001110;  // Configure RA0/AN0 as analogue
ADCON2           = 0b10101010;  // Right justified result
                                // TAD 12 and FOSC 32 - may need to adjust this
                                // depending on your clock frequency (see datasheet)
ADCON0.ADON      = 1;           // Enable ADC

Now the port should be set up, you can now read the LDR value:

ADCON0bits.GO    = 1;           // Set the GO bit of the ADCON0 register to start
                                // the conversion.

while (ADCON0bits.GO);          // Wait until the conversion is complete.

You can now read the result of the LDR as a 10-bit value in ADRESH:ADRESL. If you only need 8-bit resolution, then set ADCON2.ADFM = 0 for left justification of the result, then you only need to read the ADRESH to get your result.

Best Answer

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Get value from LDR

Electronic – Enable port RA0 as input and retrieve value LDR from led

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