Segger SystemView logging not working with NUM_UP_BUFFERS size greater than 64

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    • Segger SystemView logging not working with NUM_UP_BUFFERS size greater than 64

      I am using Renesas RX130 micro, J-Link Ultra+, FINE connection @50MHz with Segger system view for logging ISR events, this is ISR logging frequency is higher, so I allocated "SEGGER_RTT_MAX_NUM_UP_BUFFERS" more than 64 in "SEGGER_RTT_Conf.h" but if allocate this buffer size more than 64, I am getting "RTT Control block not found" in System view. after looking into SystemView log file , it says "NUM_UP_BUFFERS" greater than 64 is invalid. is there any way I can increase "SEGGER_RTT_MAX_NUM_UP_BUFFERS" more than 64, so that I can get log in SystemView logging without any buffer overflow error. If I use UP buffer size for 64, I am getting frequent buffer overflow error in Segger SystemView. :(
    • The FINE protocol supports 2 MHz max. and everything selected > 2 MHz will be scaled down to 2 MHz.
      64 buffers sounds weird…
      SystemView is not designed to have information disteibuted over multiple buffers if they belong to the same instance. If you have higher frequency ISRs, you would just need a bigger buffer but keep it at 1 buffer for SystemView.
      FINE is a very speed limited protocol, so you may overload it with RTT relatively fast.
      For FINE, J-Link needs to read 4-byte wise per FINE command.
      1 byte Cmd
      1 byte Resp
      4 bytes Data
      = 6 bytes = 60 bits (10 bits per byte due to UART / FINE protocol)
      2 MHz = 2,000,000 bits per second
      2 Mio. / 60 = 33,333 commands per second
      33,333 commands = 33,333 * 4 = 133,333 payload bytes per second.
      Meaning roughly 130 KB/s payload (without command overhead) J-Link theoretically(!) can do max. via FINE.
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