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I am struggling with the I2C interface programming with MSP430G2553 MCU. I did not plug the slave device to test it, but I expected to have at least the slave address to be send over the I2C. I use internal resistors pull ups and ACLK to clock USCI. Here is my code:
#include <msp430.h>
int main(void) {
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
DCOCTL = CALDCO_1MHZ;
BCSCTL1 = CALBC1_1MHZ;
// ACLK setup: VLO/8
BCSCTL1 &= ~XTS; // Select Low-Frequency clock
BCSCTL3 = (BCSCTL3 & ~LFXT1S_3) | LFXT1S_2; // Select VLO
BCSCTL1 = (BCSCTL1 & ~DIVA_3) | DIVA_3; // VLO/8 divider
UCB0CTL1 |= UCSWRST;
UCB0CTL0 = UCMST + UCMODE_3 + UCSYNC;
UCB0CTL1 |= UCSSEL1; // Use ACLK
UCB0BR0 = 180;
UCB0BR1 = 0;
UCB0I2CSA = 0x52;
P1SEL |= BIT7 + BIT6;
P1SEL2 |= BIT7 + BIT6;
P1REN |= BIT6 + BIT7;
P1OUT |= BIT6 + BIT7;
UCB0CTL1 &= ~UCSWRST;
__delay_cycles(200);
while (UCB0STAT & UCBBUSY);
UCB0CTL1 |= UCTR + UCTXSTT;
while (UCB0CTL1 & UCTXSTT);
UCB0TXBUF = 0x36;
while (!(UCB0TXIFG & UCB0TXIFG));
while (UCB0STAT & UCBBUSY);
UCB0CTL1 |= UCTXSTP;
while (UCB0CTL1 & UCTXSTP);
while(1);
}When debugging I see that the code gets stuck at the following line:
while (UCB0CTL1 & UCTXSTT);
The logic sniffer with the BusPirate device, shows that after initialization, both SDA and SCL are pulled high and stay in this state.
Here the Channel-0 is P1.6 (SCL); Channel-1 is P1.7 (SDA) and Channel-3 is PIN16 (RST). I use MSP-EXP430G2 Rev 1.5 launchpad for the test.
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