run software with debugger vs. standalone Launchpad 28377S - SCI fail

Hm.

I guess your code runs properly even after reset in debug mode?

Well, the main difference is that Debug-mode uses special GEL-files. These are some scripts for lots of purposes - they can clear ram-memory, when you connect, they can start/stop watchdog, when you press "Run", they are multi-purpose files, driven by your CodeComposerStudio events (attaching to MCU, flashing program, restarting and so on). This scripts can even init some peripherals.

So i think they do some special job for you, which must be done by your code. It's hard to say what should be done exactly.

You can start debug session, then in Debug Perspective go "Tools" - "GEL Files". There will be a window with availible gel-files for you MCU. Look which functions on such events as Start, Reset.

Well yes, this is possible, but not necessary. Anyway, have you muxed RX and TX properly? Can you show your init code or tell, which example have you changed?

void init_serial_com(uint32_t u32LSPCLK, uint32_t u32BaudRate) {
	char *msg;

	// MUX settings out of Table 4-1, Datasheet (SPRS880A)
	// SCI - C
	// GPIO90/EM1A17/EM1DQM2/SCIRXDC => hene UART
	// GPIO89/EM1A16/EM1DQM1/SCITXDC => hene UART
	GPIO_SetupPinMux(90, GPIO_MUX_CPU1, 6);
	GPIO_SetupPinOptions(90, GPIO_INPUT, GPIO_PUSHPULL);
	GPIO_SetupPinMux(89, GPIO_MUX_CPU1, 6);
	GPIO_SetupPinOptions(89, GPIO_OUTPUT, GPIO_ASYNC);

	UARTConfigSetExpClk(UARTC_BASE, u32LSPCLK, u32BaudRate,
	UART_CONFIG_WLEN_8 | UART_CONFIG_PAR_NONE | UART_CONFIG_STOP_ONE);

	//ScicRegs.SCILBAUD.all    = 0x0035;
	UARTFIFOEnable(UARTC_BASE);

	msg = "\r\initialized!\0";
	send_msg(msg);
}

static void send_msg(char * msg) {
	int i;
	i = 0;
	while (msg[i] != '\0') {
		scic_xmit(msg[i]);
		i++;
	}
}

static void scic_xmit(int a) {
	while (ScicRegs.SCIFFTX.bit.TXFFST != 0)
		;
	ScicRegs.SCITXBUF.all = a;
}