CC2538: ZNP: How does fragmentation work?

Jason Cole26

Part Number: CC2538

Hi guys

We are sending two fragmented packets over the air, total size of 133 bytes. This is causing the ZNP-NPI interface to bomb.

Are the fragmented packets assembled within the ZNP library and passed on to MT_AfIncomingMsg(afIncomingMSGPacket_t *pMsg) or are the individual packets passed through MT_AfIncomingMsg(afIncomingMSGPacket_t *pMsg)?

We have taken an over-the-air screenshot from Ubiqua:

over 7 years ago

0 YiKai Chen over 7 years ago

Guru 735695 points

If I remember correctly, fragmented packets would be assembled within the ZNP library and passed on to MT_AfIncomingMsg(afIncomingMSGPacket_t *pMsg)

0 Jason Cole26 over 7 years ago

Intellectual 710 points

Furthermore, in znp_app.c, we are seeing, in npUartTxReady, this condition occurring, which I believe the ZNP does not recover from:

	
    uint16 len = HalUARTWrite(HAL_UART_PORT, pMsg, npUartTxCnt);
    npUartTxCnt -= len;

    if (npUartTxCnt == 0)
    {
      osal_msg_deallocate(npUartTxMsg);
      npUartTxMsg = NULL;
    }
    else
    {
      pMsg += len;

<<<<<<<<<<<<<<<<<<<<<<<<<<< HERE

    }
  }

0 YiKai Chen over 7 years ago in reply to Jason Cole26

Guru 735695 points

If I remember correctly, the default UART TX/RX buffet is 128 and you might need to increase it.

0 Jason Cole26 over 7 years ago in reply to Jason Cole26

Intellectual 710 points

OK this appears to be due to attempting to write a 153 byte message into a UART tx buffer of 120 bytes.....

0 Jason Cole26 over 7 years ago in reply to Jason Cole26

Intellectual 710 points

Ah, HAL_UART_TX_BUF_SIZE as opposed to MT_UART_TX_BUFF_MAX

0 YiKai Chen over 7 years ago in reply to Jason Cole26

Guru 735695 points

You can try to increase buffer to 200 bytes to see if it works.

0 Jason Cole26 over 7 years ago in reply to YiKai Chen

Intellectual 710 points

I have increased it to 512 :)

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CC2538: ZNP: How does fragmentation work?