I am having trouble initializing and reading from an ADC that uses I2C to talk to my MSP430G2553. I have set breakpoints while debugging and have found that the problem occurs right after I send a start sequence. It seems that the start bit is not cleared after I send the start sequence even though that is what the data sheet told me would happen. The two functions that should be of interest are:
void initI2C_USCIB(void)
and
void sendASIADC(unsigned char location, unsigned char data);
//***************************************************************************************
// MSP430 Blink the LED Demo - Software Toggle P1.0
//
// Description; Toggle P1.0 by xor'ing P1.0 inside of a software loop.
// ACLK = n/a, MCLK = SMCLK = default DCO
//
// MSP430x5xx
// -----------------
// /|\| XIN|-
// | | |
// --|RST XOUT|-
// | |
// | P1.0|-->LED
//
// J. Stevenson
// Texas Instruments, Inc
// July 2011
// Built with Code Composer Studio v5
//***************************************************************************************
#include <msp430.h>
void transmitByteUART(unsigned char data);
void initSPI_USCIA(void); //initializes SPI on USCIA0 for the sd card reader/writer
void initI2C_USCIB(void); //initializes I2C on USCIB0 for the ADC from ASI
void initLED(void); //initializes led so we can toggle it
__interrupt void USCIAB0RX_ISR(void); //interrupt for usci
void initASIadc(void); //inits our external adc using i2c
void initUART_USCIA(void); //use this for checking the adc
void delay(unsigned long time); //simple delay function
void transmitDecimal(unsigned char data); //this sends the decimal representaton of an 8 bit number to terminal
void sendASIADC(unsigned char location, unsigned char data); //sends data to specified register to ASI ADC
void askForASIData(unsigned char channel); //input channel and should receive rx interrupt on uscib0
void readASIData(unsigned char channel); //read only used w/in askfordata
void main(void) {
WDTCTL = WDTPW | WDTHOLD; //Stop watchdog timer
//initSPI_USCIA();
//while (!(IFG2 & UCA0TXIFG)){
//IFG2 =0x00; //clear flags after waiting for tx flag
//}
//UCA0TXBUF = 0x11; //writes to spi data register
__bis_SR_register(GIE); //interrupts enabled
initLED();
initI2C_USCIB(); //inits with rx interrupt
initUART_USCIA(); //use this to check the adc with tera term
initASIadc();
while(1){
delay(1000);
askForASIData(0x00); //should cause an interrupt that sends adc stuff to teraterm
//wait for interrupt
}
}
void delay(unsigned long time){
unsigned char i = 0;
while(i<time){ //pretty simple delay function
i++;
}
}
void initSPI_USCIA(void){
P1SEL = (BIT1 | BIT2 | BIT4); //configures pins for three pin SPI. MISO P1.1, MOSI P1.2, CLK P1.4
P1SEL2 = (BIT1 | BIT2 | BIT4); //configures pins for their peripheral setting
UCA0CTL1 |= UCSWRST; //set software reset to 1 so we can configure SPI
//UCA0STAT |= UCLISTEN; //the launchpad listens to itself (use for testing)
UCA0CTL0 |= UCCKPH + UCMSB + UCMST + UCSYNC; //clkphase,clkpolarity,MSBfirst,8-bit,master mode, 3-pin, synchronous SPI
UCA0CTL1 |= UCSSEL_2; //choose SMCLK as our clock. SMCLK is 1.1 MHz. We divise it with the baud register
UCA0BR0 |= 0x02; //Baud rate is 1.1MHZ/(2+1) = 366 KHz
UCA0BR1 = 0x00; //upper byte of br register. set to zero
UCA0MCTL = 0; //No modulation
UCA0CTL1 &= ~UCSWRST; //enables the SPI to work
IE2 |= UCA0RXIE; // Enable USCI0 RX interrupt
}
void initLED(void){
P1DIR |= BIT0; //sets red led to output and turns it on
P1OUT &= ~BIT0; //turn red led off
}
void initI2C_USCIB(void){ //initializes I2C on USCIB0 for the ADC from ASI
P1SEL |= BIT6 + BIT7; // Assign I2C pins to USCI_B0
P1SEL2|= BIT6 + BIT7; // Assign I2C pins to USCI_B0
UCB0CTL1 |= UCSWRST; // Enable SW reset
UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode
UCB0CTL1 |= UCSSEL_2 + UCTR + UCSWRST; // Use SMCLK which is 1.1 MHZ, keep SW reset, receiver mode
UCB0BR0 = 60; // fSCL = SMCLK/60 = ~18.3kHz
UCB0BR1 = 0; //leave upper bits 0
UCB0I2CSA = 0x12; // Slave Address is 0x12
UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation
IE2 |= UCB0RXIE; //Enable USCI0 RX interrupt
}
void initASIadc(void){
P2DIR |= BIT0; //sets p2.0 output
P2OUT |= BIT0; //sets p2.0 HIGH. This resets the ADC
delay(100); //waits for a few clock cycles
P2OUT &= ~BIT0; //sets p2.0 LOW
sendASIADC(0x04, 0x00); //clear the ADC_CHENAB register
sendASIADC(0x00, 0x00); //sends 0x04 to the control register of Asi's ADC
sendASIADC(0x01, 0x00); //ensures that CSEND is low by clearing
sendASIADC(0x02, 0x06); //divides the 1 MHZ internal oscillator by 64 by setting ADC_CLKPRE
sendASIADC(0x03, 0x02); // ADC_CLKDV register divides the internal oscillator by 2
}
void initUART_USCIA(void){
//set clock to 1 MHZ
BCSCTL1 = CALBC1_1MHZ; // Set Digitally Controlled Oscilaltor to 1MHz
DCOCTL = CALDCO_1MHZ; // Set DCO to 1MHz
//configure hardware UART
P1SEL = (BIT1 | BIT2); //configures pins for Uart. MISO P1.1, MOSI P1.2, CLK P1.4
P1SEL2 = (BIT1 | BIT2); //configures pins for their peripheral setting
UCA0CTL1 |= UCSWRST; //set software reset to 1 so we can configure SPI
UCA0CTL0 = 0x00; //Basic 8-bit UART mode
UCA0CTL1 |= UCSSEL_2; //choose SMCLK as our clock. SMCLK is 1.1 MHz. We divise it with the baud register
UCA0BR0 |= 104; //lower baud rate register
UCA0BR1 = 0; //Baud rate is 1.1MHZ/(108+1) = 9600 (approximately)
UCA0MCTL = 0; //No modulation
UCA0CTL1 &= ~UCSWRST; //enables the UART to work
//enable RX interrupt
IE2 |= UCA0RXIE; // Enable USCI0 RX interrupt
}
void transmitByteUART(unsigned char data){
while (!(IFG2 & UCA0TXIFG)){} //waits until ready to transmit
IFG2 =0x00; //clear flags after waiting for tx flag
UCA0TXBUF = data; //send 7 to terminal
}
void transmitDecimal(unsigned char data){
unsigned char first;
unsigned char second;
unsigned char third;
first = data % 10; //this gives us the first digit /lsb of decimal
second = data/10;
second = second %10; //gives us middle digit
third = data / 100; //gives last digit
first |= 0x30; //turns it into ascii character
second |= 0x30; //turns it into ascii character
third |= 0x30; //turns it into ascii character
transmitByteUART(third);
transmitByteUART(second);
transmitByteUART(first);
transmitByteUART(0x0A); //new line
transmitByteUART(0x08); //carriage return
transmitByteUART(0x08); //carriage return
transmitByteUART(0x08); //carriage return
}
void sendASIADC(unsigned char location, unsigned char data){ //sends data via spi to asi's adc
//UCB0CTL1 |= UCTXNACK; //precede start condition with NACK
UCB0CTL1 |= UCTXSTT; //send start sequence
while(UCB0CTL1 & UCTXSTT){
//wait for start sequence to be sent
}
UCB0TXBUF = 0x24; //send i2c address of slave w/ lsb as 0 for write and 1 for read
UCB0TXBUF = location; //send internal register number
UCB0TXBUF = data; //send data byte to selected register in adc
UCB0CTL1 |= UCTXSTP; //send stop sequence
while(UCB0CTL1 & UCTXSTP){
//wait for stop sequence to be sent
}
}
void askForASIData(unsigned char channel){
unsigned char bitNum;
unsigned char controlSettings;
bitNum = 0x01 << channel; //sets the bit to 1 that is the channel number
sendASIADC(0x04, bitNum); //puts the selected bit high in the ADC_CHENAB register
controlSettings = channel << 2; //shifts channel by two so it's in the correct position for CTRL register
controlSettings |= 0x01; //or it with 1 to start the conversion
sendASIADC(0x00, controlSettings); //selects the desired channel and starts the conversion
delay(10000); //just wait for the conversion to complete
readASIData(channel); //should try to read from the selected channel
sendASIADC(0x04, 0x00); //clear the ADC_CHENAB register in preparation for the next read
}
void readASIData(unsigned char channel){
UCB0CTL1 |= UCTXSTT; //send start sequence
while(UCB0CTL1 & UCTXSTT){
//wait for start sequence to be sent
}
UCB0TXBUF = 0x24; //send i2c address of slave w/ lsb as 0 for write
channel += 0x08; //dac register
UCB0TXBUF = channel; //send internal register number(for DAC reg)
UCB0CTL1 |= UCTXSTT; //Send a start sequence again (repeated start)
while(UCB0CTL1 & UCTXSTT){
//wait for start sequence to be sent
}
UCB0TXBUF = 0x25; //send i2c address of slave w/ lsb as 1 for read
UCB0CTL1 |= UCTXSTP; //send stop sequence
while(UCB0CTL1 & UCTXSTP){
//wait for stop sequence to be sent
}
}
#pragma vector = USCIAB0RX_VECTOR
__interrupt void USCIAB0RX_ISR(void){
unsigned char data;
if(IFG2 & UCA0RXIFG){
data = UCA0RXBUF; //reading should clear the RX int flag
}
else if(IFG2 & UCB0RXIFG){
data = UCB0RXBUF;
}
transmitDecimal(data); //sends data to terminal
P1OUT |= BIT0; //turns led on
//UCA0TXBUF = UCB0RXBUF; //sends adc data to terminal
//IFG2 = 0x00; //clears flags
}
