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CY8CKIT-042: Buffer Overflow of USB-UART Bridge - KBA87869

CY8CKIT-042: Buffer Overflow of USB-UART Bridge - KBA87869

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Version: *A




  1. Why do I get continuous data flow from the USB-UART Bridge of CY8CKIT-042 even if the Tx and Rx terminals of the bridge are not connected?
  2. Why does the input buffer of the USB-UART Bridge overflow on CY8CKIT-042? 

Answer: If the physical connections of the USB-UART Bridge (shown in Figure 1) are made before opening the COM port interfacing applications such as hyperterminal, PuTTY, TeraTerm, or any other software application that reads data from the KitBridge COM interface, you might run into a UART read buffer overflow condition in the Bridge. This condition occurs when there is continuous data transfer from the UART connections of the bridge, but the PC does not read this data until the COM port interface application is invoked. If buffer overflow happens, you will observe continuous inflow of data in the COM port interface software even if there is no communication on the UART side of the KitBridge. The current bridge firmware does not clear the buffer overflow flag when it is set and hence the inflow of data through the COM port interface continues even if the physical connections to the UART (Tx, Rx) are removed.

This issue is found in the KitProg firmware revision 2.02 and got fixed in the later version of the KitProg. It’s recommended that you upgrade to the latest version of the KitProg.