Hi,
I'm trying to get the MSP430F249 UCB1 working in 3 pin SPI mode.
This is the code I'm using to initialize the Interface:
// SPI-Hardware initialisieren ////////////////////////////////////////////////
UCB1CTL1 = 1<<UCSWRST; // SPI-Controller Reset
UCB1CTL1 |= UCSSEL_1; // ACLK
UCB1CTL0 = UCCKPH + UCMSB + UCMST + UCSYNC + UCMODE_0; // Phase und Polarität, MSB-First, Master
UCB1BR0 = 4; // Prescaler 4 -> 0.9MHz
UCB1BR1 = 0;
P5SEL |= (1<<1)|(1<<2)|(1<<3); // SPI-Leitungen aktivieren
UC1IE |= UCB1RXIE;
UCB1CTL1 &= ~UCSWRST;
In the ISR of UCB1 I'm just doing a dummy read;
//UART_ISR
#pragma vector=USCIAB1RX_VECTOR
__interrupt void SPIB1_RX (void)
{ rx_data=UCB1RXBUF; }
In the main-loop I'm trying to repeatedly send 0xAA (recognizeable pattern 10101010) using the following code:
while(1)
{
spi_adresse(1,0,0); // set CS
while (!(UC1IFG & UCB1TXIFG)); // buffer ready?
UCB1TXBUF = 0xAA; // send 0xAA, start transfer
while(UCB1STAT & UCBUSY); // transmission done?
spi_adresse(0,0,0); // reset CS
}
this is how the data looks like on a logic-analyzer:
As you can see the controller sends out 7 zeros on the first transmission then stops and resets chip-select. After it starts the second transmission it sends out the same data (not 0xAA) repeatedly. It hangs at "while(UCB1STAT & UCBUSY);".
Because of 7 and not 8 clocks at the first transmission I tried setting the UC7BIT in the UCB1CTL0-register. The controller then sends out only 6 bits at the first transmission. The behaviour after the second transmission is the same, it clocks out data forever.
I just built a second board but it has the exact same behavior, so it shouldn't be a defective µC.
I'm using CCS 5.1.
What am I doing wrong?
Andreas Wenzel
