• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 40 subscribers
  • Views 612 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Apparent latency in tx udp packets

Ciaran Mac Aonghusa
Intellectual 985 points

Hi All,

V1.11.1 + CC3000. Use case is that I have a UDP socket bound to a port. Receiving packets from a far end and sending immediate response. The packets ultimately come from an app with a UI so latency here is very important.

My observation is that I see a packet leaving my AP, hits my CC3000, transferred to host by polling, processed, then response is submitted to the CC3000. Picking up the packet seems ok, and processing time is tens of milliseconds, then it is submitted to the CC3000. Now there seems a peculiarly long delay before the CC3000 submits the packe to the network. I am attempting to run this send / receive fast enough to make client UI responsive. But the latency introduced by the CC3000 is killing responsiveness.

Is there a technical explanation for why the CC3000 seems so slow?

Is there a configuration that can be used to improve this?

Thanks for your advice,

Ciarán Mac Aonghusa

  • 0
    TI__Mastermind 27095 points

    Hi Ciaran,

    What do you observe when you are individually receiving and individually sending the packets? Does it work smoothly?

    Theoretically it should be straight forward. Unless the reception traffic is too high, in which case you may want to queue some packets at the host and not block the CC3000 while sending the data to the host. This would allow CC3000 to have more space during transmission.

    Thanks & Regards,
    Raghavendra

  • 0 in reply to Raghavendra Shenoy
    Intellectual 985 points

    In fact what I discovered with the help of some TI support is that the problem was regular scanning. My scan settings were a default suggested in the basic app and so on. It meant that every couple of seconds - even when connected -- the wifi was doing a scan. This was causing the delay of several  hundred ms. I now turn off the scanning when connected, and only turn it back on again when I need to connect ( I do not use auto connect anyway and I'm not even sure if turning off scanning prevents auto connect).


    My assumption was that scanning would not be carried out by the device when connected. My problem is resolved. But can anyone explain why the device might want to continue a scan routine even when connected?

    Thanks

    Ciarán

  • 0 in reply to Ciaran Mac Aonghusa
    Prodigy 50 points

    Ciarán,

    thanks for sharing, that sounds very similar to what I observe. I send a 280 bytes udp packet every 100 ms and even on an empty network sometimes there are quite big delays (or even missing pakets). How do you turn scanning off, just by calling: wlan_ioctl_set_scan_params(0, 20, 30, 2, 0x7ff, -80, 0, 205, aiIntervalList) ?

    Thanks,

    Markus