ARM LPC2138/48 Mini Development Board – POT Interfacing (ADC)
LPC 2138/48 has two 10-bit successive approximation ADC s. ADC0 has 6 channels & ADC1 has 8 channels. The maximum possible input to ADC is 3.3V which gives output reading as 1023(The maximum value that can be represented in 10 bits). Thus the resolution is 3.3V/1024=3.22 mV.The development board has a POT connected to pin P0.29 i.e, AD0.2 via jumper J12. On varying the POT, voltage ranging from 0-3.3V gets applied to ADC input.
Sample code to check the ADC module of LPC 2148 with potentiometer is given below. The output is displayed on LCD and the variation can be checked with the POT.
Schematic
Note: To check ADC with POT, don’t forget to short jumper J12. Leaving it open frees P0.29 and can be used for any other desired purpose.
Sample Code
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/******************************************************************************** HEADER FILES *********************************************************************************/ #include<lpc213x.h> #define RS 0x00020000 /* RS - P1.17 */ #define RW 0X00040000 /* R/W - P1.18 */ #define EN 0X00080000 /* E - P1.19 */ #define CLR 0X00FE0000 unsigned int adc_value=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 to be given * *********************************************************************************/ 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 to be given * *********************************************************************************/ 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) << 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 */ 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) << 20; /* Taking the second 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_Data * * * * Description : Function to display single character on LCD * * * * Parameters : data - character to be displayed * *********************************************************************************/ 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) << 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 */ 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)<<20; /* Taking the second 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_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 initialize 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 : ADC_Conversion * * * * Description : Function to get ADC reading * * * * Parameters : None * *********************************************************************************/ int ADC_Conversion() { int ab; /* Variable to store ADC value */ Delay(1); AD0CR = AD0CR|0x01000000; /* Start conversion */ while((AD0DR&0x80000000)!=0x80000000); /* Wait here till conversion is over */ ab = (AD0DR&0x0000FFC0); /* Extracting the result */ ab = (ab>>6); /* Shift 6 bits right */ return ab; /* Return the result */ } /******************************************************************************** * Function : Int_ASCII * * * * Description : Function to store integer value in array * * * * Parameters : value - value to be stored * * cnt - no: of digits * *********************************************************************************/ void Int_ASCII(int value,char cnt) { int i = 0; /* Local variables */ char array[7]; int values; values = value; for(i=1; i<=cnt; i++) /* Store the received value in array */ { array[i] = values%10; values = values/10; } for(i=cnt; i>=1; i--) /* Display it on LCD */ { LCD_Data(array[i]+'0'); } } /******************************************************************************** * Function : ADC_Check * * * * Description : Function to take ADC reading & display it on LCD * * * * Parameters : None * *********************************************************************************/ void ADC_Check() { AD0CR=0x00200604; /* PDN=1,CLKDIV=6,channel=AD0.2 */ LCD_Command1(0x80); LCD_String("ADC Checking...."); LCD_Command1(0xC0); LCD_String("ADC:"); adc_value=ADC_Conversion(); /* Get the result of conversion */ LCD_Command1(0xC4); /* 2nd row, 5th location */ Int_ASCII(adc_value,4); /* Display the result on LCD */ Delay(100); } /******************************************************************************** * Function : PORT_Initial * * * * Description : Function to initialize PORTs * * * * Parameters : None * *********************************************************************************/ void PORT_Initial(void) { IO1DIR = 0x00FE0000; /* LCD pins set as o/p */ PINSEL0 = 0x00000000; PINSEL1 = 0x05000000; /* ADC function for 0.28 & 0.29 */ PINSEL2 = 0x00000000; } /******************************************************************************** MAIN FUNCTION *********************************************************************************/ int main() { PORT_Initial(); /* Initialise the ports */ LCD_Init(); /* Initialise LCD */ LCD_Command1(0x80); /* 1st row, 1st location */ LCD_String("ADC Checking."); LCD_Command1(0x01); /* Clear screen */ while(1) { ADC_Check(); /* Take ADC reading */ } } /***************************** END OF PROGRAM *********************************/ |
Topics related to ARM LPC2138/48 Mini Development Board
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