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Dear Sirs:
Found out that I have to use interrupts to send a slave address and one byte of data. So added interrupts to my simple example.
The program does send the slave address but never sends the data=200dec. If I put a break point at the top of the interrupt routine it will also send
a stop condition, otherwise it only sends the slave address. Appears to me it conforms to the example in the manual but still doesn't work right.
Any ideas, please?
Thanks, John
The code:
#include <msp430.h>
unsigned int TXByteCtr;
unsigned char *pTxData;
int A;
typedef unsigned char uint8;
/******************************************************************************
Test I2C MSP430FR5994
Simple I2C transmitter using interrupts. To be used to write to an electronic pot.
Transmits I2C TxData out P5.0 and P5.1
Originally from Dang
******************************************************************************/
int main(void)
{
int i;
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
PM5CTL0 &=~LOCKLPM5; //disable GPIO power on default
UCB1CTL1 |= UCSWRST; // Enable SW reset
P5SEL0 |= BIT0 ; //UCB1SIMO
P5SEL0 |= BIT1 ; //UCB1SOMI
//P5SEL0 |= BIT3 ; //UCB1STE (slave tx enable)
P5SEL1 &= ~BIT0 ; //UCB1SIMO
P5SEL1 &= ~BIT1 ; //UCB1SOMI
//P5SEL1 &= ~BIT3 ; //UCB1STE (slave tx enable)
//UCMODE_3 sets I2C mode
UCB1CTLW0 |= (UCMST + UCMODE_3 + UCTR); // I2C Master, I2C, transmitter
UCB1CTLW1 = UCASTP_2 ; // Automatic stop assertion
UCB1BRW = 8; // fSCL = SMCLK/12 = ~100kHz
UCB1TBCNT =2; // 2 bytes data
//UCB1BR1 = 0;
UCB1I2CSA = 0x1; // Slave Address is 1ah
UCB1CTL1 &= ~UCSWRST; // Clear SW reset, resume operation
UCB1IE |= UCTXIE; // Enable TX interrupt for UCB1IE
_enable_interrupts(); //global ie
TXByteCtr = 1; // Load TX byte counter
UCB1TXBUF = 200; // Load TX buffer with pot value
UCB1CTLW0 |= UCTXSTT; // I2C TX, start condition this transmits! UCTR is bit 4(0x10) of UCBxCTLW0
while (1)
{
// while (UCB1CTL1 & UCTXSTP); // Ensure stop condition got sent
// UCB1CTL1 |= UCTR + UCTXSTT; // I2C TX, start condition
// __bis_SR_register(CPUOFF + GIE); // Enter LPM0 w/ interrupts
// Remain in LPM0 until all data
A=A+1; // is TX'd
loop :
// UCB1TXBUF = TxData; // Load TX buffer new !!
for(i=0;i<10000;i++) //delay while sending
A=A+1;
}
}
//------------------------------------------------------------------------------
// The USCIAB0TX_ISR is structured such that it can be used to transmit any
// number of bytes by pre-loading TXByteCtr with the byte count.
//
//------------------------------------------------------------------------------
//#pragma vector = USCI_B1_VECTOR
//__interrupt void isr_usci_b1(void){
#pragma vector = USCI_B1_VECTOR
__interrupt void USCI_B1_ISR(void){
static int IFlags;
IFlags = UCB1IFG;
if (TXByteCtr) // Check TX byte counter
{
UCB1TXBUF = 200; // Load TX buffer
TXByteCtr--; // Decrement TX byte counter
IFlags = UCB1IFG;
UCB1CTLW0 |= UCTXSTT; // I2C TX, start condition
UCB1IFG &= ~UCTXIFG; // Clear USCI_B1 TX int flag
}
else
{
UCB1CTL1 |= UCTXSTP; // I2C stop condition
UCB1IFG &= ~UCTXIFG; // Clear USCI_B1 TX int flag
//__bic_SR_register_on_exit(CPUOFF); // Exit LPM0
}
}
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