This is the code I use for both UARTs in all my MSP430 code bases, and
I've never run into a problem with it. Are you handling yours differently?
--jc
int putcharx (int data)
{
unsigned char tmphead = (UART0_TxHead + 1) & UART0_TX_BUFFER_MASK;
while (tmphead == UART0_TxTail)
;
_DINT ();
UART0_TxBuf [UART0_TxHead = tmphead] = data;
if (!(IE1 & UTXIE0))
{
IE1 |= UTXIE0;
IFG1 |= UTXIFG0;
}
_EINT ();
return (data);
}
interrupt (UART0TX_VECTOR) uart0tx_interrupt (void)
{
int tmptail;
if (UART0_TxHead != UART0_TxTail)
U0TXBUF = UART0_TxBuf [UART0_TxTail = (UART0_TxTail + 1) &
UART0_TX_BUFFER_MASK];
else
IE1 &= ~UTXIE0;
}
Steve Underwood wrote:
James Henry Dodd wrote:
Hi Robert,
If things aren't working, are you sure you followed the UART setup
sequence
properly?
Quoting slau049c.pdf from Texas:
"...
The required USART initialization/re-configuration process is:
1) Set SWRST (BIS.B #SWRST,&UxCTL)
2) Initialize all USART registers with SWRST = 1 (including UxCTL)
3) Enable USART module via the MEx SFRs (URXEx and/or UTXEx)
4) Clear SWRST via software (BIC.B #SWRST,&UxCTL)
5) Enable interrupts (optional) via the IEx SFRs (URXIEx and/or UTXIEx)
Failure to follow this process may result in unpredictable USART
behavior.
..."
IMHO, the behaviour isn't unpredictable: it's sure not to work! :)
Cheers,
James
It is somewhat unpredictable, but you are right - it doesn't work
correctly. However, even following this procedure I have encountered
something odd. When you initially enable the transmit interrupt you
would expect am immediate tx empty interrupt (unless you had just
stuffed a value into TXBUF). That is what happens with most UARTS.
However, I have found I need to write a value into TXBUF to kick the
interrupt mechanism into life. After that, the tx empty interrupts
occur as expected.
Regards,
Steve
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