9 Replies Latest reply on Jul 9, 2012 7:08 AM by userc_42819

    UART Rx buffer size

      am using psoc3 and i need to recieve 30 bytes in Rxbuffer of UART[v2.10].
      i have made my buffer size 30 as well as the Rxinterrupt is also generated.
      but only first 4 bytes are recieving properly , ferther bytes are getting overwrite on these bytes.
      My config is
      Full UART [Tx +Rx]
      clock selection -> internal clock
      Rx Address Config -> Add Mode -> Software Byte by byte
                ->Add# 1 & 2->0
      Break signal bits->12
      Enable 2 out of 3 voting per bit

      Rx & Tx buffer size 30 Bytes
      oversampling rate -> 8x

      how can i recieve all 30 bytes as it is in Rxbuffer?

        • 1. Re: UART Rx buffer size

          First, if you do not have multiple devices on a serial bus, you should disable all that addressing features of the UART which may interfere with your needs.


          When using the buffer mechanism the interrupt for receiving a byte is disabled, thus leaving you only the method to poll for a message received or to look for any bytes already in the buffer. I assume you are reading bytes off the FIFO whichs size is 4 so getting your incomplete data. You will have to read the data off the buffer  with UART_GetChar() while querying with UART_GetRxBufferSize() for data received.


          To give you furter help, it is advisable to upload your project here, using the "Create Workspace Bundle"-command after cleaning the design.





          • 2. Re: UART Rx buffer size

            Thanks for your reply

            sir, as per your guideline am polling bytes from buffer & querying with UART_GetRxBufferSize() for data received.
            but am getting output for once only.whenever am showing card next time the program control is hanging in UART_GetRxBufferSize() in log_in_sector.
            so how can i remove this.
            also am using Mifare_reader_ClearRxBuffer() in each function, & the data remains in buffer as it is????
            is there any mistake in my method of querying for buffersize?

            • 3. Re: UART Rx buffer size

              my project file is attached

              • 4. Re: UART Rx buffer size

                sorry its here

                • 6. Re: UART Rx buffer size

                  ohhh dont know why the attachment is not uploading

                  am transmitting 4 bytes by PutArray,
                  waiting by while(Mifare_reader_GetRxBufferSize()<=4);
                  recieving 10 bytes by GetChar(),
                  clearing rx buffer,


                  transmitting 12 bytes,
                  waiting by while(Mifare_reader_GetRxBufferSize()<=4);  <-Here it hangs whenever i shows card next time
                  recieving 5 bytes,
                  clearing rx buffer,


                  transmitting 5 bytes,
                  waiting by while(Mifare_reader_GetRxBufferSize()<=4);
                  recieving 21 bytes,
                  clearing rx buffer


                  printing data


                  i have made rx & tx buffer size 22 & break signal bits 13.

                  • 7. Re: UART Rx buffer size

                    You may send your zipped project-file to my personell address, which is briefe@jmeiersoftware.de., I'll try to upload it to this forum (you're not the only one having problems uploading a file).


                    From your work you described in your post, there seems to be a transmition going on but some chars seem to get dropped. did you ever try to look at some of the error-bits in the RxStatus()? Note that tese bits are cleared upon a read!.


                    Debugging while interrupts from hardware become pending sometimes look as if the program refuses to re-start from a breakpoint, so do not let you get confused about that.


                    I normally do not use BREAKs in UART-transmitions, they are used afaik for keeping a connection open preventing it from beeing dropped because of no traffic occured too long. If you can, do not use break.




                    A rather simple way of thesting an UART connection is to cross-connect the RXses and TXses and send out in a loop everything you receive. The cross-connect can be made PSoC internally to exclude any additional hardware or later to include driver, cable etc.



                    • 8. Re: UART Rx buffer size

                      Having a look into ypur program reveiled the following:


                      the function select_card() was processed and you are hanging in log_in_sector()


                      The reason for that is:


                      You check the buffer for containing 4 characters and then you're reading off 21 bytes without checking for chars available.


                      The polling for GetRxBufferSize() is disabling the interrupt for a short time and that's where you are looping. The count of received characters does not match the number of chars you expect.


                      Since this will always stall your program I would suggest to put all the receive-communication with the Mifare_reader into a single function with a parameter indicating how many chars you expect and as return-value how many chars you received. To keep this function from stalling in a dead-loop I would suggest to set up a timer which you start at entry and that can abort waiting for the chars.


                      Also, if not really needed, I would suggest to abandon the break-bits.


                      May I upload your project to the community?





                      • 9. Re: UART Rx buffer size

                        Another idea just came up:


                        I do not know the protocol you are using with the Mifare_reader, but rather often the last character sent by a peripheral is <Cr> or <Lf> which are 0x0d or 0x0a respectively. Will it not be better instead of counting chars receiving chars until a 0x0a or 0x0d occurs?



                        • 10. Re: UART Rx buffer size

                          I tried your ideas but still bytes were missing.


                          so i replace buffersize by BufferWrite i.e. now i am checking Mifare_reader_rxBufferWrite .


                          i think checking Mifare_reader_rxBufferWrite doesnt disable intrupt. so now getting exact output as expected.