UART transmission seems to be working weirdly

Question

I created a simple driver call for UART transmission and when I debug the program and put breakpoints at every transmission, it seems to work fine (I see the characters sent being printed to the serial console) but when I run the program without any breakpoints, all I see is "?" being printed to the console. 
 
 The receiver part works fine: as soon as I enter a character in serial, I see an IRQ handler getting fired where the value is read off RXD register. . // main.cpp

Uart&#160;uart;&#160;&#160;

int main()
{
&#160; &#160; char s[] = "hello";

&#160; &#160; uart.StartTx((uint8_t *) s, strlen(s));
}

// uart.cpp
bool Uart::getNrfEventStatus(nrf_uart_event_t reg) const
{
 return (bool) *(volatile uint32_t *)((uint8_t *)pUARTx + (uint32_t)reg);	
}
void Uart::TxByte(uint8_t byte)
{
 setNrfEvent(NRF_UART_EVENT_TXDRDY, 0); 
 pUARTx->TXD = byte;
}

void Uart::TxBlocking(uint8_t *buffer, size_t bytesToSend)
{
 for (uint8_t idx = 0; idx < bytesToSend; idx++)
 { 
 TxByte(buffer[idx]); // NRF_UART_EVENT_TXDRDY is set right after writing to TXD
 bool volatile txdRdyEvnt = getNrfEventStatus(NRF_UART_EVENT_TXDRDY); &#160;
while (txdRdyEvnt); // wait till NRF_UART_EVENT_TXDRDY is reset in IRQ handler
 } 
}

 void Uart::StartTx(uint8_t *buffer, size_t bytesToSend) 
{ 
 setNrfEvent(NRF_UART_EVENT_TXDRDY, 0); 
 setNrfEvent(NRF_UART_TASK_STARTTX, 1); // trigger NRF_UART_TASK_STARTTX
 TxBlocking(buffer, bytesToSend); 
 setNrfEvent(NRF_UART_TASK_STOPTX, 1); 
}

void Uart::setNrfEvent(T reg, uint32_t value) // TODO - change fctn name 
{ 
 *((volatile uint32_t *)((uint8_t *)pUARTx + (uint32_t)reg)) = value; 
 #if __CORTEX_M == 0x04 
 volatile uint32_t dummy = *( (volatile uint32_t *) ((uint8_t *)pUARTx + (uint32_t)reg) ); 
 (void)dummy; 
 #endif 
} Thanks for the help

morpho · Accepted Answer

Well, the issue certainly was with the flags. 
 - First issue: `while (txdRdyEvnt); `isn't taking into account the updated value. 
 - Second: the following flow and disabling TxdRdy interrupt flag did the trick! 
 void Uart::TxBlocking ( uint8_t *buffer, size_t bytesToSend) 
{
 for ( uint8_t idx = 0 ; idx < bytesToSend; idx++)
 { 
 setNrfEvent(NRF_UART_EVENT_TXDRDY, 0 );
 TxByte(buffer[idx]);
 while (getNrfEventStatus(NRF_UART_EVENT_TXDRDY) == 0 );
 }
}