Trying to interface MSP430G2553 with SRF02 ultrasonic ranger finder, nothing is working.
Several problems, appreciate answer to any of them:
- On the connection side: the srf02 is a 5V device while the MSP430 is a 3.3V device. On the srf02, datasheet says i2c SDA and SCL should be pulled up to 5V, while the MSP430 warns to not pull up anything above 3.3V.
So what should I do? Right now I’m trying to pull it up to 5V with a 10k resistor, but with an inline resistor of 1k. Will this work? I'm trying to get it to work, and not worrying about performance issues currently.
2. On the datasheet it says the Device Address is 0xE0, so for MSP430 is it 0xE0 or 0x70?
3. Also, I’ve been trying weeks to do the coding part in CCS. I’m trying to do the following idea (it’s all from the datasheet):
I2c_init();
I2c_write(0x70); (or 0xE0 don’t know which one is right)
I2c_write(0x00);
I2c_write(0x51);
I2c_stop();
Right now I can’t even implement this properly (i try to write 3 bytes in, but the code won't even get to the second byte(0x00)). The code below (very long) is mostly the same as an example code written by Mr. Dang from TI. I changed some parts:
If anyone can see any glaring errors in the part I changed (indicated in bold below). It would help immensely.
#include <msp430.h>
//1.6
#define NUM_BYTES_TX 3 // How many bytes?
#define NUM_BYTES_RX 1
int RXByteCtr, RPT_Flag = 0; // enables repeated start when 1
volatile unsigned char RxBuffer[128]; // Allocate 128 byte of RAM
unsigned char *PTxData; // Pointer to TX data
unsigned char *PRxData; // Pointer to RX data
unsigned char TXByteCtr, RX = 0;
int txc, rxc = 0;
unsigned char test = 0;
unsigned char TxData[] = {0x70,0x00,0x51}; //data trying to send
void Setup_TX(void);
void Setup_RX(void);
void Transmit(void);
void Receive(void);
int flag = 0;
int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
P1SEL |= BIT6 + BIT7; // Assign I2C pins to USCI_B0
P1SEL2|= BIT6 + BIT7; // Assign I2C pins to USCI_B0
while(1){
//Transmit process
Setup_TX();
RPT_Flag = 1;
Transmit();
if(flag==1)
{
P1DIR |= BIT0;
P1OUT |= 0x01;
}
while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent
//Receive process
Setup_RX();
Receive();
while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent
}
}
//-------------------------------------------------------------------------------
// The USCI_B0 data ISR is used to move received data from the I2C slave
// to the MSP430 memory. It is structured such that it can be used to receive
// any 2+ number of bytes by pre-loading RXByteCtr with the byte count.
//-------------------------------------------------------------------------------
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{ // does the transmitting & receiving
//Rx = 1 is master receive mode
if(RX == 1){ // Master Receive?
RXByteCtr--; // Decrement RX byte counter
if (RXByteCtr)
{
*PRxData++ = UCB0RXBUF; // Move RX data to address PRxData
}
else
{
if(RPT_Flag == 0)
UCB0CTL1 |= UCTXSTP; // No Repeated Start: stop condition
if(RPT_Flag == 1){ // if Repeated Start: do nothing
RPT_Flag = 0;
}
*PRxData = UCB0RXBUF; // Move final RX data to PRxData
__bic_SR_register_on_exit(CPUOFF); // Exit LPM0
}
}
else{ //Rx = 0 master transmitter mode // Master Transmit
if (TXByteCtr) // Check TX byte counter
{ //I changed this part
UCB0TXBUF = TxData[txc]; // Load TX buffer
txc = txc + 1; //until here
flag = 1;
TXByteCtr--; // Decrement TX byte counter
}
else
{
if(RPT_Flag == 1){
RPT_Flag = 0;
PTxData = (unsigned char *)TxData; // TX array start address
TXByteCtr = sizeof TxData; // Load TX byte counter
// PTxData = *MSData; // TX array start address
// TXByteCtr = NUM_BYTES_TX; // Load TX byte counter
__bic_SR_register_on_exit(CPUOFF);
}
else{
UCB0CTL1 |= UCTXSTP; // I2C stop condition
IFG2 &= ~UCB0TXIFG; // Clear USCI_B0 TX int flag
__bic_SR_register_on_exit(CPUOFF); // Exit LPM0
}
}
}
}
void Setup_TX(void){ //unchanged
_DINT();
RX = 0;
IE2 &= ~UCB0RXIE;
while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent// Disable RX interrupt
UCB0CTL1 |= UCSWRST; // Enable SW reset
UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode
UCB0CTL1 = UCSSEL_2 + UCSWRST; // Use SMCLK, keep SW reset
UCB0BR0 = 12; // fSCL = SMCLK/12 = ~100kHz
UCB0BR1 = 0;
UCB0I2CSA = 0x70; // Slave Address
UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation
IE2 |= UCB0TXIE; // Enable TX interrupt
}
void Setup_RX(void){ //unchanged
_DINT();
RX = 1;
IE2 &= ~UCB0TXIE;
UCB0CTL1 |= UCSWRST; // Enable SW reset
UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C Master, synchronous mode
UCB0CTL1 = UCSSEL_2 + UCSWRST; // Use SMCLK, keep SW reset
UCB0BR0 = 12; // fSCL = SMCLK/12 = ~100kHz
UCB0BR1 = 0;
UCB0I2CSA = 0x70; // Slave Address
UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation
IE2 |= UCB0RXIE; // Enable RX interrupt
}
void Transmit(void){ //changed first two lines to account for multiple byte sending
PTxData = (unsigned char *)TxData; // TX array start address
TXByteCtr = sizeof TxData; // Load TX byte counter
// PTxData = *MSData; // TX array start address
// TXByteCtr = NUM_BYTES_TX; // Load TX byte counter
while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent
UCB0CTL1 |= UCTR + UCTXSTT; // I2C TX, start condition
__bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts
}
void Receive(void){ //changed first two lines
PRxData = (unsigned char *)RxBuffer; // Start of RX buffer
RXByteCtr = NUM_BYTES_RX; // Load RX byte counter
while (UCB0CTL1 & UCTXSTP); // Ensure stop condition got sent
UCB0CTL1 |= UCTXSTT; // I2C start condition
__bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts
}
