ARM LPC2129 Mini Development Board – Switches Interfacing
ARM LPC2129 Mini Development Board has 3 Switches (SW1,SW2 & SW3) connected to port pins P0.14, P0.15 & P0.16 via jumpers J4, J5 & J6 respectively. 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:
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(SW1/ SW2 /SW3) gets displayed on the LCD. In circuit pull-ups has been provided to all three switches.
Sample Code
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/********************************************************************************* HEADER FILES **********************************************************************************/ #include<lpc21xx.h> #define RS 0x00020000 /* RS - P1.17 */ #define RW 0X00040000 /* R/W - P1.18 */ #define EN 0X00080000 /* E - P1.19 */ #define CLR 0X00FE0000 /********************************************************************************* VARIABLE DECLARATION **********************************************************************************/ volatile unsigned int key_scan=0; unsigned char key_count=0; /********************************************************************************* * Function : Delay * * * * Description : Function for Delay * * * * Parameters : x - Delay time * **********************************************************************************/ int Delay(unsigned int x) { x=x*12000; while(x!=0) { x--; } return 0; } /********************************************************************************* * Function : LCD_Command * * * * Description : Function to give command to LCD * * * * Parameters : command - command * **********************************************************************************/ void LCD_Command(char command) { int Temp; IO1CLR = CLR; /* Clearing the port pins */ IO1SET = EN; /* Enable pin high */ IO1CLR = RS; /* RS=0 for command register */ IO1CLR = RW; /* R/W=0 for write */ Temp = (command & 0xF0) << 16; /* Taking the first nibble of command */ IO1SET = IO1SET | Temp; /* Writing it to data line */ Delay(2); IO1CLR = EN; /* Enable pin low to give H-L pulse */ } /********************************************************************************* * Function : LCD_Command1 * * * * Description : Function to give command to LCD * * * * Parameters : command1 - command * **********************************************************************************/ void LCD_Command1(char command1) { int Temp; IO1CLR = CLR; /* Clearing the port pins */ IO1SET = EN; /* Enable pin high */ IO1CLR = RS; /* RS=0 for command register */ IO1CLR = RW; /* R/W=0 for write */ Temp = (command1 & 0xF0); /* Taking the first nibble of command */ Temp = Temp << 16; /* Shift it 16 bits to left */ IO1SET = IO1SET | Temp; /* Writing it to dataline(P1.20-P1.23)*/ Delay(2); IO1CLR = EN; /* Enable pin low to give H-L pulse */ IO1CLR = CLR; /* Clearing the port pins */ IO1SET = EN; /* Enable pin high */ IO1CLR = RS; /* RS=0 for command register */ IO1CLR = RW; /* R/W=0 for write */ Temp = (command1 & 0x0F); /* Taking the second nibble of command*/ Temp = Temp << 20; /* Shift it 20 bits to left */ IO1SET = IO1SET | Temp; /* Writing it to data line */ Delay(2); IO1CLR = EN; /* Enable pin low to give H-L pulse */ } /********************************************************************************* * Function : LCD_Data * * * * Description : Function to give data for displayto LCD * * * * Parameters : data - data * **********************************************************************************/ void LCD_Data(char data) { int Temp; IO1CLR = CLR; /* Clearing the port pins */ IO1SET = EN; /* Enable pin high */ IO1SET = RS; /* RS=1 for data register */ IO1CLR = RW; /* R/W=0 for write */ Temp = (data & 0xF0); /* Taking the first nibble of data */ Temp = Temp << 16; /* Shift it 16 bits to left */ IO1SET = IO1SET | Temp; /* Writing it to data line */ Delay(2); IO1CLR = EN; /* Enable pin low to give H-L pulse */ IO1CLR = CLR; /* Clearing the port pins */ IO1SET = EN; /* Enable pin high */ IO1SET = RS; /* RS=1 for data register */ IO1CLR = RW; /* R/W=0 for write */ Temp = (data & 0x0F); /* Taking the second nibble of data */ Temp = Temp << 16; /* Shift it 20 bits to left */ IO1SET = IO1SET | Temp; /* Writing it to data line */ Delay(2); IO1CLR = EN; /* Enable pin low to give H-L pulse */ } /********************************************************************************* * Function : LCD_String * * * * Description : Function to display string on LCD * * * * Parameters : String to be displayed * **********************************************************************************/ void LCD_String(unsigned char *dat) { while(*dat!='\0') /* Check for termination character */ { LCD_Data(*dat); /* Display the character on LCD */ dat++; /* Increment the pointer */ } } /********************************************************************************* * Function : LCD_Init * * * * Description : Function to initialise LCD * * * * Parameters : None * **********************************************************************************/ void LCD_Init(void) { Delay(15); LCD_Command(0x30); Delay(10); LCD_Command(0x30); Delay(5); LCD_Command(0x30); LCD_Command(0x20); LCD_Command1(0x28); LCD_Command1(0x01); /* Clear display */ LCD_Command1(0x06); /* Auto increment */ LCD_Command1(0x0C); /* Cursor off */ } /********************************************************************************* * Function : Key_Check * * * * Description : Function to check keypress * * * * Parameters : None * **********************************************************************************/ void Key_Check(void) { IO0CLR = 0X0001C000; key_scan = IO0PIN & 0X0001C000; /* Reading PORT0 */ if(key_scan!=0X0001C000) /* Checking for key press */ { Delay (10); if(key_scan==0X00018000) /* If SW1 is pressed, P0.14 gets low */ { LCD_Command1(0xC5); /* Command for 2nd row, 6th position */ LCD_String("SW1"); /* Display on LCD */ while((IO0PIN&0X0001C000)!=0X0001C000); /* Wait till switch is released */ } if(key_scan==0X00014000) /* If SW2 is pressed, P0.15 gets low */ { LCD_Command1(0xC5); /* Command for 2nd row, 6th position */ LCD_String("SW2"); /* Display on LCD */ while((IO0PIN&0X0001C000)!=0X0001C000); /* Wait till switch is released */ } if(key_scan==0X0000C000) /* If SW3 is pressed, P0.16 gets low */ { LCD_Command1(0xC5); /* Command for 2nd row, 6th position */ LCD_String("SW3"); /* Display on LCD */ while((IO0PIN&0X0001C000)!=0X0001C000); /* Wait till switch is released */ } } } /********************************************************************************* * Function : PORT_Initial * * * * Description : Function for PORT Initialisation * * * * Parameters : None * **********************************************************************************/ void PORT_Initial(void) { IO1DIR = 0x00FE0000; /* LCD pins set as o/p */ IO0DIR = 0x00000000; /* PORT0 set as i/p */ PINSEL0 = 0x00000000; PINSEL1 = 0x00000000; PINSEL2 = 0x00000000; } /********************************************************************************* MAIN FUNCTION **********************************************************************************/ int main() { PORT_Initial(); /* Initialise the ports */ LCD_Init(); /* Initialise LCD */ LCD_String("Rhydo Technology"); LCD_Command1(0xC0); /* 2nd row */ LCD_String(" Cochin "); LCD_Command1(0x01); /* Clear screen */ LCD_Command1(0x80); /* 1st row */ LCD_String("KEY Checking."); while(1) { Key_Check(); /* Check for key press */ } } |
Topics related to ARM LPC2129 Mini Development Board
- ARM LPC2129 Mini Development Board – Overview
- ARM LPC2129 Mini Development Board – LED Interfacing
- ARM LPC2129 Mini Development Board – LCD Interfacing
- ARM LPC2129 Mini Development Board – UART0 Interfacing
- ARM LPC2129 Mini Development Board – UART1 Interfacing
- ARM LPC2129 Mini Development Board – Switches Interfacing
- ARM LPC2129 Mini Development Board – BUZZER Interfacing
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- ARM LPC2129 Mini Development Board – Temperature Sensor Interfacing(ADC)
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