One method that is commonly used is to have the microcontroller simply send its data block over and over again. This way there needs to be no handshake between the PC and the microcontroller. The scheme works well if the data being sent is a small amount and represents a real time readout.

For example, if your device was reporting the weight of an object you could send the weight data as a packet of eight ASCII digits with a single quote character as a packet beginning marker and followed by a carriage return as an end of packet marker. This could be sent 5 times per second to the PC as follows:

  '00014557<cr> '00014557<cr>  '00014563<cr> 

The incoming data can then be captured by the PC. On the PC side if no data is seen within 1/5 second then you know there is a problem with the RS232 connection or the microcontroller. The PC would loop looking for data until it first saw the packet lead-in quote character so as to synchronize with the data flow.

Michael Karas