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MSP-EXP430FR6968 UART interrupt RX doesn't work

Other Parts Discussed in Thread: MSP430FR6989

I'm using this code from in this thread.

All jumpers are connect. When I send a character to PC works fine but when I try to receive the character from PC the interrupt doesn't release. I used the original code from texas instruments using UCA0 and removing the RXD/TXD jumpers from the "bridge" header (J101) and patch the P2.0 (J1.8) pin to TXD and P2.1 (J2.19) pin to RXD and I have the same problem. I can send character from launchpad but I cand receive from PC (interrupt doesn't launch). Any idea?

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//******************************************************************************
//  MSP430FR69xx Demo - eUSCI_A0 UART echo at 9600 baud using BRCLK = 8MHz
//
//  Description: This demo echoes back characters received via a PC serial port.
//  SMCLK/ DCO is used as a clock source and the device is put in LPM3
//  The auto-clock enable feature is used by the eUSCI and SMCLK is turned off
//  when the UART is idle and turned on when a receive edge is detected.
//  Note that level shifter hardware is needed to shift between RS232 and MSP
//  voltage levels.
//
//  The example code shows proper initialization of registers
//  and interrupts to receive and transmit data.
//  To test code in LPM3, disconnect the debugger.
//
//  ACLK = VLO, MCLK =  DCO = SMCLK = 8MHz
//
//                MSP430FR6989
//             -----------------
//       RST -|     P2.0/UCA0TXD|----> PC (echo)
//            |                 |
//            |                 |
//            |     P2.1/UCA0RXD|<---- PC
//            |                 |
//
//   William Goh
//   Texas Instruments Inc.
//   April 2014
//   Built with IAR Embedded Workbench V5.60 & Code Composer Studio V6.0
//******************************************************************************
// modified by: Peter Spevak
//
// last change: April 7th 2020
//
// 04/07/2020 changing the UART to eUSCIA1, as this is the UART for
//            backchannel on virtual COM port to PC
//
//*****************************************************************************
#include <msp430.h>

int main(void)
{
  WDTCTL = WDTPW | WDTHOLD;                 // Stop Watchdog

  // Configure GPIO
  //P2SEL0 |= BIT0 | BIT1;                    // USCI_A0 UART operation         // 04/07/2020
  //P2SEL1 &= ~(BIT0 | BIT1);                                                   // 04/07/2020
  P3SEL0 |= BIT4 + BIT5;                    // eUSCI_A1 UART                    // 04/07/2020
  P3SEL1 &= ~(BIT4 + BIT5);                 // eUSCI_A1 UART                    // 04/07/2020

  // Disable the GPIO power-on default high-impedance mode to activate
  // previously configured port settings
  PM5CTL0 &= ~LOCKLPM5;

  // Startup clock system with max DCO setting ~8MHz
  CSCTL0_H = CSKEY >> 8;                    // Unlock clock registers
  CSCTL1 = DCOFSEL_3 | DCORSEL;             // Set DCO to 8MHz
  CSCTL2 = SELA__VLOCLK | SELS__DCOCLK | SELM__DCOCLK;
  CSCTL3 = DIVA__1 | DIVS__1 | DIVM__1;     // Set all dividers
  CSCTL0_H = 0;                             // Lock CS registers

  // Configure USCI_A0 for UART mode
  /*UCA0CTLW0 = UCSWRST;                      // Put eUSCI in reset             // 04/07/2020
  UCA0CTLW0 |= UCSSEL__SMCLK;               // CLK = SMCLK
  // Baud Rate calculation
  // 8000000/(16*9600) = 52.083
  // Fractional portion = 0.083
  // User's Guide Table 21-4: UCBRSx = 0x04
  // UCBRFx = int ( (52.083-52)*16) = 1
  UCA0BR0 = 52;                             // 8000000/16/9600
  UCA0BR1 = 0x00;
  UCA0MCTLW |= UCOS16 | UCBRF_1 | 0x4900;
  UCA0CTLW0 &= ~UCSWRST;                    // Initialize eUSCI
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt
*/

  // Configure USCI_A1 for UART mode
  UCA1CTLW0 = UCSWRST;                      // Put eUSCI in reset               // 04/07/2020
  UCA1CTLW0 |= UCSSEL__SMCLK;               // CLK = SMCLK                      // 04/07/2020
  // Baud Rate calculation
  // 8000000/(16*9600) = 52.083
  // Fractional portion = 0.083
  // User's Guide Table 21-4: UCBRSx = 0x04
  // UCBRFx = int ( (52.083-52)*16) = 1
  UCA1BR0 = 52;                             // 8000000/16/9600                  // 04/07/2020
  UCA1BR1 = 0x00;                                                               // 04/07/2020
  UCA1MCTLW |= UCOS16 | UCBRF_1 | 0x4900;                                       // 04/07/2020
  UCA1CTLW0 &= ~UCSWRST;                    // Initialize eUSCI                 // 04/07/2020
  UCA1IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt      // 04/07/2020

  __bis_SR_register(LPM3_bits | GIE);       // Enter LPM3, interrupts enabled
  __no_operation();                         // For debugger
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCI_A0_VECTOR))) USCI_A0_ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(UCA0IV, USCI_UART_UCTXCPTIFG))
  {
    case USCI_NONE: break;
    case USCI_UART_UCRXIFG:
      while(!(UCA0IFG&UCTXIFG));
      UCA0TXBUF = UCA0RXBUF;
      __no_operation();
      break;
    case USCI_UART_UCTXIFG: break;
    case USCI_UART_UCSTTIFG: break;
    case USCI_UART_UCTXCPTIFG: break;
  }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)            // 04/07/2020
#pragma vector=USCI_A1_VECTOR
__interrupt void USCI_A1_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(USCI_A1_VECTOR))) USCI_A1_ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(UCA1IV, USCI_UART_UCTXCPTIFG))
  {
    case USCI_NONE: break;
    case USCI_UART_UCRXIFG:
      while(!(UCA1IFG&UCTXIFG));
      UCA1TXBUF = UCA1RXBUF;
      __no_operation();
      break;
    case USCI_UART_UCTXIFG: break;
    case USCI_UART_UCSTTIFG: break;
    case USCI_UART_UCTXCPTIFG: break;
  }
}

  • Hi Jose,

    Are you using CCS? If you have an active debug session running that can interfere with the backchannel/PC UART connection. Can you try flashing your program, terminating the debug session, resetting the device, and performing your test again?

    Regards,

    Evan

  • Thanks for your reply Evan, but i did your recommendations and doesn't works. I can't launch the interrupt RX from UCA1 (or UCA0). Anyone can test this code on launchpad MSP430FR6989?

  • Can you clarify your intended configuration? In the code you posted above you are using USCI_A1. USCI_A1 is connected to ports P3.4/P3.5 which go directly to jumper J101. 

    However, you also say that your are removing the RXD and TXD jumper on J101 and connecting P2.0/P2.1 to TXD/RXD ezFET side of J101. 

    It sound like you have half of one configuration and half of the other. You must either:

    • Use USCI_A1 with the jumpers across TXD/RXD on J101
    • Use USCI_A0 with a wires from P2.0/P2.1 to the TXD/RXD on the ezFET side of J101.

    Regards,

    Evan

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