Hi all,
I will appritiate your help in configuring uart.
My MSP is MSP430f5438a
I am currently developing onthe MSP-EXP430F5438 Experimenter Board.
I am trying to configure MCu to use the board's oscilator running at 20mhz
My problem is that te uart sometimes drops few bytes.
Here is a snippet of the code
Thank you for your help...
#define CLOCK_FREQ_MHZ 20000000
#define CLOCK_FREQ_KHZ (CLOCK_FREQ_MHZ / 1000)
#define RATIO (CLOCK_FREQ_MHZ / 32768) //20000000/32768 = 610.351 (20Mhz/32khz)
void main(void)
{
//FLL init to 20Mhz
PDOUT = 0;
PDDIR = 0xFFFF;
PDSEL = BIT0 + BIT1;
LFXT_Start(XT1DRIVE_0);
Init_FLL_Settle(CLOCK_FREQ_KHZ, RATIO);
uart_data_init();
whlie(1)
{
uart_data_write(); //writing to uart
//sleep enough time to prevent cyclic buffer from being overrun
}
}
void uart_data_init()
{
P3SEL |= BIT4 + BIT5; // P3.4,5 = USCI_A0 TXD/RXD
UCA0CTL1 |= UCSWRST; // **Put state machine in reset**
UCA0CTL1 |= UCSSEL_2; // SMCLK
UCA0BR0 = 130; // 20MHz 9600
UCA0BR1 = 0; // 20MHz 9600
UCA0MCTL = UCBRS_0 + UCBRF_3 + UCOS16; // Modln UCBRSx=0, UCBRFx=3, over sampling
UCA0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**
UCA0IE = UCRXIE; //enable Receive interrupt
}
int uart_data_write(byte *pdata, int data_len)
{
//disable Tx interrupts
UCA0IE &= ~UCTXIE;
//Add data to cyclic buffer
//enable Tx interrupts. when tx interrupts are enabled isr is invoked which causes
//to write to uart the data we stored in the cyclic buffer
UCA0IFG |= UCTXIFG;
UCA0IE |= UCTXIE;
return ret_val;
}
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
{
switch (__even_in_range(UCA0IV, 4))
{
case 0:
break; // Vector 0 - no interrupt
case 2: // Vector 2 - RXIFG
//Read from cyclic buffer
break;
case 4: // Vector 4 - TXIFG
if ( g_tx_cyclic_start == g_tx_cyclic_end)
{//buffer empty. there is nothing to send
return;
}
//send to uart
UCA0TXBUF = g_tx_cyclic_buff[g_tx_cyclic_end];
g_tx_cyclic_end = ( g_tx_cyclic_end + 1 ) % CYCLIC_BUFF_SIZE;
break;
default:
break;
}
}
