MSP430FR5994 UART communication with PC in python

Question

I try to learn how to use UART and for starters I want to just send something from the microcontroller to the PC. I orient myself with this code files.

Microcontroller: MSP430FR5994 LaunchPad Development Kit

UART: FTDI cable to Pins 2.6(UCA1RXD) and 2.5(UCA1TXD)

The microcontroller is programmed using CCS on a virtualbox Windows machine. The python script is run with python3 on the main linux system.

What I have done so far:

Python Script for Receiving

import serial                                     # import pySerial module
ComPort = serial.Serial('/dev/ttyUSB0',timeout=1) # open ttyUSB0

ComPort.baudrate = 9600                           # set Baud rate
ComPort.bytesize = 8                    # Number of data bits = 8
ComPort.parity   = 'N'                  # No parity
ComPort.stopbits = 1                    # Number of Stop bits = 1

data = ComPort.read()               # Wait and read data from serial port
print(data)                             # print the received data

ComPort.close()                         # Close the COM Port

C Script for Microcontroller

#include <msp430.h> 
void UART_init(void);

void main(void) {
  WDTCTL = WDTPW | WDTHOLD;   //Stop watchdog timer
  PM5CTL0 &= ~LOCKLPM5;

  UART_init();

  UCA1TXBUF = 'A';

}

void UART_init(void){
    P2SEL1 |= BIT5 + BIT6;              //Activate Pin for UART use
    P2SEL0 &= ~BIT5 + ~BIT6;            //Activate Pin for UART use

    UCA1CTLW0 |= UCSSEL_2;              //Select clock SMCLK

    UCA1BRW = 0x6;                      //Set Baud rate 9600 : UCA1BRW = INT(F_CPU/BAUD_soll) =         INT(1MHz/9600) = 104 with oversampling: 6
    UCA1MCTLW |= UCBRS5 + UCOS16 + UCBRF3;     //Modulation according to datasheet table: UCBRS = 0x20 = b100000 and UCOS16 = 1 and UCBRF = 8 = 0x8 = b1000

    UCA1CTLW0 &= ~UCSWRST;  //Reset UART module
 }

Then I flash the microcontroller code and afterwards run the python code. But I do not get anything. After the timeout of 1s I just get b''.

Where could be the error? Is there no communication? Are the pins wrong? As I am just learning it, I am really clueless why it is not working. Maybe you have some suggestions :)

Regards, straumle

DONE SO FAR So I tried the following things and it is still not working:

enter low power mode

#include <msp430.h> 
void UART_init(void);

void main(void) {
  WDTCTL = WDTPW | WDTHOLD;   //Stop watchdog timer
  PM5CTL0 &= ~LOCKLPM5;

  UART_init();

  UCA1TXBUF = 'A';
  __bis_SR_register(LPM0_bits);

}

void UART_init(void){
    P2SEL1 |= BIT5 + BIT6;              //Activate Pin for UART use
    P2SEL0 &= ~BIT5 + ~BIT6;            //Activate Pin for UART use

    UCA1CTLW0 |= UCSSEL_2;              //Select clock SMCLK

    UCA1BRW = 0x6;                      //Set Baud rate 9600 : UCA1BRW = INT(F_CPU/BAUD_soll) =         INT(1MHz/9600) = 104 with oversampling: 6
    UCA1MCTLW |= UCBRS5 + UCOS16 + UCBRF3;     //Modulation according to datasheet table: UCBRS = 0x20 = b100000 and UCOS16 = 1 and UCBRF = 8 = 0x8 = b1000

    UCA1CTLW0 &= ~UCSWRST;  //Reset UART module
}

and never exit with a while(1) loop with and without entering low power mode

#include <msp430.h> 
void UART_init(void);

void main(void) {
  WDTCTL = WDTPW | WDTHOLD;   //Stop watchdog timer
  PM5CTL0 &= ~LOCKLPM5;

  UART_init();

  while(1){
  UCA1TXBUF = 'A';
  __bis_SR_register(LPM0_bits); // with and without the entering LPM0 mode
  }
}

void UART_init(void){
    P2SEL1 |= BIT5 + BIT6;              //Activate Pin for UART use
    P2SEL0 &= ~BIT5 + ~BIT6;            //Activate Pin for UART use

    UCA1CTLW0 |= UCSSEL_2;              //Select clock SMCLK

    UCA1BRW = 0x6;                      //Set Baud rate 9600 : UCA1BRW = INT(F_CPU/BAUD_soll) =         INT(1MHz/9600) = 104 with oversampling: 6
    UCA1MCTLW |= UCBRS5 + UCOS16 + UCBRF3;     //Modulation according to datasheet table: UCBRS = 0x20 = b100000 and UCOS16 = 1 and UCBRF = 8 = 0x8 = b1000

    UCA1CTLW0 &= ~UCSWRST;  //Reset UART module
 }

I also tried inserting

 while(!(UCA1IFG & UCTXIFG));

in both scenarios. Finally, I also tried it with an interrupt:

#include <msp430.h> 
void UART_init(void);

void main(void) {
  WDTCTL = WDTPW | WDTHOLD;   //Stop watchdog timer
  PM5CTL0 &= ~LOCKLPM5;

  UART_init();

  __bis_SR_register(LPM0_bits + GIE);

}

void UART_init(void){
    P2SEL1 |= BIT5 + BIT6;              //Activate Pin for UART use
    P2SEL0 &= ~BIT5 + ~BIT6;            //Activate Pin for UART use

    UCA1CTLW0 |= UCSSEL_2;              //Select clock SMCLK

    UCA1BRW = 0x6;                      //Set Baud rate 9600 : UCA1BRW = INT(F_CPU/BAUD_soll) =         INT(1MHz/9600) = 104 with oversampling: 6
    UCA1MCTLW |= UCBRS5 + UCOS16 + UCBRF3;     //Modulation according to datasheet table: UCBRS = 0x20 = b100000 and UCOS16 = 1 and UCBRF = 8 = 0x8 = b1000

    UCA1CTLW0 &= ~UCSWRST;  //Reset UART module
    UCA1IE |= UCTXIE;       //enable transmitting interrupts
}

#pragma vector= EUSCI_A1_VECTOR
__interrupt void USCI_A1_ISR(void){
   while(!(UCA1IFG & UCTXIFG)); //with and without this line
   UCA1TXBUF = 'A';
}

Answer 1

Ok wow! I found my mistake... It is a really stupid one... The following line brought me up to it:

Also remember that UART connections cross from device to device. MSP430 UART TX -> External Device UART RX and MSP430 UART RX <- External Device UART TX.

I am really sorry! Everything is working fine now that I have switched the cables. Puh a little embarrassing. But hey, it works now :D

Thanks @CL for your answers and your patience.