Hello -
I am testing the CC2543 USART in SPI Slave mode, using the transmit interrupt to update the value in U0DBUF. However, it seems a UTX0 interrupt is being generated every 8 SCLK (P0_5) cycles, regardless of the state of SSN (P0_4). My SSN signal toggles every 32 SCLK cycles. The false UTX0 interrupts are a problem, since I get several UTX0 interrupts when SSN is inactive and in fact a single byte hasn't actually been clocked out of the transmit buffer! When I look at the behavior of the URX0 interrupt, it appears to be functioning properly and only generates interrupts while SSN is actually active and bytes are actually being clocked into the receive buffer... In our application, the loading of data to the USART must eventually be done by DMA, so I need to resolve this.
FROM MY MAIN:
/***************************************************************************
* Configure SPI
*/
// Configure USART0 for Alternative 1 => Port P0 (PERCFG.U0CFG = 0).
PERCFG = (PERCFG & ~PERCFG_U0CFG) | PERCFG_U0CFG_ALT1;
PPRI &= ~PPRI_PRI0P0; // Give priority to USART 0 over Timer 1 for port 0 pins.
P0SEL |= BIT5 | BIT4 | BIT3 | BIT2; // Set pins 2, 3, 4 and 5 as peripheral I/O.
// Set USART to SPI mode and Slave mode.
U0CSR = (U0CSR & ~U0CSR_MODE) | U0CSR_SLAVE;
U0BAUD = SPI_BAUD_M;
U0GCR = (U0GCR & ~(U0GCR_BAUD_E | U0GCR_CPOL | U0GCR_CPHA)) | U0GCR_ORDER | SPI_BAUD_E;// MSB first
//enable the interrupt USART0 TX: IEN2.UTX0IE
IEN2 |= IEN2_UTX0IE; // Enable interrupt
txBufferINDEX = 0;
U0DBUF = txBufferINDEX;
...
MY INTERRUPT:
#pragma vector = UTX0_VECTOR
__interrupt void uart_TX_ISR(void)
{
IRCON2 = ~UTX0IF; // clear the interrupt flag the proper way
P1_4 = 1; // so I can easily see the interrupt on a scope
txBufferINDEX++; // will wrap, but that's ok.
U0DBUF = txBufferINDEX; // just load the VALUE of the index
P1_4 = 0; // so I can easily see the interrupt on a scope
}
Thanks,
- Art
