ARM LPC2138/48 Mini Development Board – Internal Real Time Clock (RTC)
Sample code to use the internal RTC of LPC 2138/48 is given below. Here seconds, minutes & hour are initialized to 0. Time gets updated every second and is displayed on LCD in the format hh:mm:ss.
Changing the initial time : To change the initial time, just load the desired values into the corresponding registers HOUR, MIN & SEC.
Running the RTC : If you want to run the RTC forever after loading the initial values, follow these steps
- Ensure that the RTC battery is placed in battery holder.
- Flash the code.
- Comment the lines which load the initial values of time.
- Build the code & flash it again
Sample Code
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/************************************************************************************* HEADER FILES **************************************************************************************/ #include<lpc21xx.h> unsigned char flag=0; /************************************************************************************* INTERRUPT SERVICE ROUTINE **************************************************************************************/ void RTC_int(void)__irq { ILR = 0X01; /* Clears counter increment interrupt */ flag = 1; /* Set flag on interrupt */ VICVectAddr = 0X00000000; } /************************************************************************************* * Function : RTC_Init * * * * Description : Function to initialize internal RTC * * * * Parameters : None * **************************************************************************************/ void RTC_Init() { ILR = 0X03; /* Interrupt from counter increment block */ CCR = 0X11; /* RTC Time counters enable */ CIIR = 0X01; /* Interrupt generated in each second */ SEC = 0x00; /* Load initial value into seconds register*/ MIN = 0x00; /* Load initial value into minutes register*/ HOUR = 0x00; /* Load initial value into hour register */ VICIntEnable = 0x00002000; /* RTC interrupt enabled */ VICVectCntl0 = 0x0000002D; /* RTC interrupt assigned to slot0 */ VICVectAddr0 = (unsigned)RTC_int; } /************************************************************************************* * Function : Delay * * * * Description : Function for delay * * * * Parameters : b - delay time * **************************************************************************************/ void Delay(unsigned long b) { while (--b!=0); /* Decrement b for delay */ } /************************************************************************************* * Function : Write_Command * * * * Description : Function to give command to LCD * * * * Parameters : cmd - command * **************************************************************************************/ void Write_Command(int cmd) { IO1CLR |= 0x00f00000; /* Clear D4-D7 */ IO1CLR |= 0x00040000; /* Read/Write = 0 */ IO1CLR |= 0X00020000; /* RS = 0,Command register */ IO1SET |= 0x00f00000 & cmd; /* Set D4-D7 */ IO1SET |= 0X00080000; /* Enable - high */ Delay(30000); IO1CLR |= 0x00080000; /* Enable - low */ } /************************************************************************************* * Function : Write_Data * * * * Description : Function to display data on LCD * * * * Parameters : dat - character to be displayed * **************************************************************************************/ void Write_Data(int dat) { IO1CLR |= 0x00f00000; /* Clear D4-D7 */ IO1CLR |= 0x00040000; /* Read/Write = 0 */ IO1SET |= 0X00020000; /* RS = 1,Data register */ IO1SET |= 0x00f00000 & dat; /* Set D4-D7 */ IO1SET |= 0X00080000; /* Enable - high */ Delay(30000); IO1CLR |= 0x00080000; /* Enable - low */ } /************************************************************************************* * Function : LCD_Data * * * * Description : Function to give data to display on LCD * * * * Parameters : dat - data * **************************************************************************************/ void LCD_Data(char dat) { Write_Data(dat << 16); Write_Data(dat << 20); } /************************************************************************************* * Function : LCD_Command * * * * Description : Function to give command to LCD * * * * Parameters : cmd - command * **************************************************************************************/ void LCD_Command(char cmd) { Write_Command(cmd << 16); Write_Command(cmd << 20); } /************************************************************************************* * Function : LCD_String * * * * Description : Function to display string on LCD * * * * Parameters : String to be displayed * **************************************************************************************/ void LCD_String(char *CPtr) { while(*CPtr != '\0') /* Check for string termination */ { LCD_Data(*CPtr); /* Display the character */ CPtr++; /* Increment the pointer */ Delay(20000); } } /************************************************************************************* * Function : LCD_Init * * * * Description : Function to initialize LCD * * * * Parameters : None * **************************************************************************************/ void LCD_Init(void) { IO1DIR |= 0x00FE0000; /* Set P1.17-P1.23 as output */ Delay(200000) ; Write_Command(0x30 << 16); Delay(100000); Write_Command(0x30 << 16); Delay(100000); Write_Command(0x30 << 16); Delay(100000); Write_Command(0x20 << 16); /* Enable 4 bit mode */ LCD_Command(0x01); /* Clear display */ LCD_Command(0x06); /* Auto address inc */ LCD_Command(0x0c); /* Cursor off */ LCD_Command(0x80); /* First location */ } /************************************************************************************* MAIN FUNCTION **************************************************************************************/ int main(void) { LCD_Init(); /* Initialize LCD module */ RTC_Init(); /* Initialize RTC module */ while(1) { if(flag) { LCD_Command(0x80); /* 1st row, 1st location */ flag=0; /* Clear flag */ LCD_Data(HOUR/10 + '0'); /* Display hour */ LCD_Data(HOUR%10 + '0'); LCD_Data(':') ; LCD_Data(MIN/10 + '0'); /* Display Minute */ LCD_Data(MIN%10 + '0'); LCD_Data(':') ; LCD_Data(SEC/10 + '0'); /* Display Second */ LCD_Data(SEC%10 + '0'); } } } /******************************* END OF PROGRAM ************************************/ |
Topics related to ARM LPC2138/48 Mini Development Board
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- ARM LPC2138/48 Mini Development Board – Internal Real Time Clock (RTC)
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