PIC18F4520 – Interfacing Switch
PIC18F4520 Mini Development Board has 3 Switches (SW1,SW2 & SW3) connected to port pins RC3, RC2 & RB5 via jumpers J8, J9 & J15 respectively. These switches are externally pulled up to +5V. On shorting these jumpers, the switches can be used as pull_up keys and if the jumpers are left open, then the port pins can be used independently.
Schematic
Note: To use the pull-up keys, don’t forget to short the jumpers J8, J9 & J15. Leaving them open frees RC3, RC2 & RB5 and can be used for any other desired purpose.
Sample Code
Sample code to test the switches is given below. In the code, switch press is detected by polling and upon pressing a switch, its name gets displayed on the LCD.
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/************************************************************************* HEADER FILES **************************************************************************/ #include<pic18.h> /************************************************************************* FUNCTION DECLARATIONS **************************************************************************/ void Delay_us(int us); void Data(int Value); void Cmd(int Value); void Send2Lcd(const char Adr, const char *Lcd); /************************************************************************* MAIN FUNCTION **************************************************************************/ void main() { TRISC = 0X0C; /* RC1(EN),RC0(RS)->O/P,RC3(SW1),RC2(SW2)->I/P */ TRISD = 0X00; /* PORTD(LCD data lines) configured as output */ TRISB5= 1; Delay_us(25); Cmd(0X30); /* LCD Specification Commands */ Delay_us(25); Cmd(0X30); /* LCD Specification Commands */ Delay_us(25); Cmd(0X30); /* LCD Specification Commands */ Delay_us(25); Cmd(0X38); /* Double Line Display Command */ Cmd(0X06); /* Auto Increment Location Address Command */ Cmd(0X0C); /* Display ON Command */ Cmd(0X01); /* Clear Display Command */ Delay_us(1000); while(1) { if(RC3==0) /* If SW1 is pressed, RC3 gets low */ { Send2Lcd(0x80,"SW1 PRESSED "); } else if(RC2==0) /* If SW2 is pressed, RC2 gets low */ { Send2Lcd(0x80,"SW2 PRESSED "); } else if(RB5==0) /* If SW3 is pressed, RB5 gets low */ { Send2Lcd(0x80,"SW3 PRESSED "); } else { Send2Lcd(0x80,"NO SW PRESSED "); } } } /************************************************************************* * Function : Cmd * * * * Description : Function to send a command to LCD * * * * Parameters : Value - Command to be given * **************************************************************************/ void Cmd(int Value) { PORTD = Value; RC0 = 0; /* RC5=0(RS=0 for command Register Selection) */ RC1 = 1; /* RC1=1(Enable=1, Enable pin high) */ Delay_us(25); RC1 = 0; /* RC1=0(Enable=1, Enable pin low) */ } /************************************************************************* * Function : Data * * * * Description : Function to display a character on LCD * * * * Parameters : Value - Character to be displayed * **************************************************************************/ void Data(int Value) { PORTD = Value; RC0 = 1; /* RC5=1(RS=1 for command Register Selection) */ RC1 = 1; /* RC1=1(Enable=1, Enable pin high) */ Delay_us(25); RC1 = 0; /* RC1=0(Enable=1, Enable pin low) */ } /************************************************************************* * Function : Send2Lcd * * * * Description : Function to send string of data to LCD * * * * Parameters : Adr, contains the adddress of a string * **************************************************************************/ void Send2Lcd(const char Adr, const char *Lcd) { Cmd(Adr); /* Address of location to display string */ while(*Lcd!='\0') /* Check for termination character */ { Data(*Lcd); /* Display the character on LCD */ Lcd++; /* Increment the pointer */ } } /************************************************************************* * Function : Delay_us * * * * Description : Function for 1 microsecond delay * * * * Parameter : us - delay in microseconds * **************************************************************************/ void Delay_us(int us) { us = us>>1; while(us!=1) us--; } /*************************** END OF PROGRAM ****************************/ |
Topics related to PIC18F4520 Mini Development Board
- PIC18F4520 Mini Development Board – Overview
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- PIC18F4520 Mini Development Board – Interfacing LCD
- PIC18F4520 Mini Development Board – Serial communication(USART)
- PIC18F4520 Mini Development Board – Interfacing Switch
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