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Fixed edge case that might lead to Serial beeing stuck in spinlook wait #307

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Fixed edge case that might lead to Serial beeing stuck in spinlook wait #307

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17 changes: 15 additions & 2 deletions cores/HardwareSerial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -185,6 +185,17 @@ if(( XMC_USIC_CH_GetTransmitBufferStatus( _XMC_UART_config->channel ) == XMC_USI
int nextWrite = _tx_buffer->_iHead + 1;
if( nextWrite >= SERIAL_BUFFER_SIZE )
nextWrite = 0;

//This should always be false but in case transmission is completed before head is advanced at the end of this function we might get stuck in an infinte loop at the spinlook stage
if( XMC_USIC_CH_GetTransmitBufferStatus( _XMC_UART_config->channel ) != XMC_USIC_CH_TBUF_STATUS_BUSY ) {
//Reenable IRQ and send Data
XMC_UART_CH_EnableEvent( _XMC_UART_config->channel, XMC_UART_CH_EVENT_TRANSMIT_BUFFER );
XMC_UART_CH_Transmit( _XMC_UART_config->channel, _tx_buffer->_aucBuffer[ _tx_buffer->_iTail ] );
_tx_buffer->_iTail++;
if(_tx_buffer->_iTail >= SERIAL_BUFFER_SIZE)
_tx_buffer->_iTail = _tx_buffer->_iTail - SERIAL_BUFFER_SIZE; //This should be interchangeable with iTail = 0 but I like this style more as it provides a correct value if iTail is larger than Serial Buffer Size (which should never be the case)
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Could you please simplify the comments, for example by keeping only the “//Reenable IRQ and send Data”

}

while( _tx_buffer->_iTail == nextWrite )
; // Spin locks if we're about to overwrite the buffer. This continues once the data is sent

Expand Down Expand Up @@ -232,12 +243,14 @@ if( ( status & XMC_UART_CH_STATUS_FLAG_TRANSMIT_BUFFER_INDICATION ) != 0U )
if( _tx_buffer->_iTail >= SERIAL_BUFFER_SIZE )
_tx_buffer->_iTail = 0;
}
else
else {
// Mask off transmit interrupt so we don't get it any more
XMC_UART_CH_DisableEvent( _XMC_UART_config->channel, XMC_UART_CH_EVENT_TRANSMIT_BUFFER );
XMC_UART_CH_DisableEvent( _XMC_UART_config->channel, XMC_UART_CH_EVENT_TRANSMIT_BUFFER );
}
}
}

//****************************************************************************
// END OF FILE
//****************************************************************************

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