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WiFi Module - reliable TCP stream

Former Member

Hello,

I am looking for a suitable WiFi module that can handle TCP streaming without any hiccups in AP mode. Some WiFi modules that I have looked at before are the ESP8266, WF121 and WINC1500.

With all three of the above I am experiencing frequent 500ms to 1000ms'stalls when trying to send TCP packets at around 200Hz I do not have anything fancy in place just calling the TCP send function as fast as I can and reading as fast as I can on my laptop(packets are fairly small at around  30-10030-100 bytes

The WINC1500 probably has less of this problem, and the stall is a lot more frequent in AP mode then it is in STA mode.

Is this issue something that has to be handled in software? Or is there hardware that is capable of this? I am finding it hard to believe that I am experiencing this with all 3 modules...

Any guidance on this problem would be very much appreciated

  • I would take a look at what was in common with these tests and check that something in software/hardware is causing the trouble. Since no setup information given, that is all I can suggest. I have used a Arduino Yun in AP mode to the internet with no troubles at all.

    Clem

  • in reply to clem57

    Clem,

    thank you for your reply. I have tested this on 3 different modules, all on a different board (including the WINC1500 on their own development board) all set as AP and TCP server sending data out to a TCP receiver. The receiving side has been on 2 different laptops and 2 different phones with all the same result image. The issue is greatly minimised when the WINC1500 is in STA rather then AP mode, but their support can not recreate my problem, driving me mad.
    I'm not too sure where else to turn, I believe the problem all stems from the modules ability to handle and send high amount of packets while maintaining AP mode..

    I would still consider myself new to this, am I expecting too much from a low-power wifi module?

  • in reply to Former Member

    Is this network traffic going through a router? A previous blog had this same problem and found the router was the cause.

  • Hi George,

     

    CC3200 in AP mode can achieve close to twice your 200 packets per sec desired rate at least, according to here:

    https://e2e.ti.com/support/wireless_connectivity/simplelink_wifi_cc31xx_cc32xx/f/968/t/356680

    As Clem says, you need to diagnose a bit further because there is a whole system here, not a single module.

    Anywhere in the system - module, your source code, the wireless stack, the API type (Python, C, etc), build method

    (instrumented or not), firmware, air interface, router/switch, remote device) could have an issue.

    Anyway, as mentioned the CC3200 will exceed your requirement.

  • in reply to clem57

    My system is roughly: The WiFI module as AP. and an external device connected to it.
    I then have UART or SPI transfer data to the WiFi Module and then have that transmitted over TCP.

     

    The information coming into the SPI or UART will be a continuous stream and I cant afford any packet loss or any hiccups in the transfers, at least not with good connection.

  • in reply to Former Member

    If you are running on bare metal (no OS), how do you handle information from the external device at the same time transmitting thru WiFi? If you program both on the same processor, you should be using interrupts to smoothly do both together. Some TCP/IP software runs in blocking mode not allowing interrupts. Check which calls/APIs are being used. The Yun I mentioned earlier has the external device connected to the AVR which is separate from the processor handling handing the WiFi with a bridge to communicate.

    754px-Yun_Bridge_Diagram.png

     

    Clem

  • in reply to shabaz

    Hello shabaz,

    I have looked at that, but where I am worried is that even though it is rated at a high transfer rate, If there is ever a 500ms or 1000ms gap in the transmission (on a strong connection) then I would have a problem.. My project requires constant and stable data streaming, as it will be used for automatic controlling and half a second to a second gap in data transfer is unacceptable. the WINC1500 had a PHY throughput of 72Mps and had some impressive transfer speeds, but had very obvious gaps in the transmissions when in AP mode.

  • in reply to Former Member

    Hi George,

         When you put a Wi-Fi in AP mode, you cause that device to broadcast a beacon 10 times a second asking for anyone to join. Why would you want this extra overhead if you have critical information to send? See Wi-Fi modes of operation (802.11 or Wi-Fi) for a complete discussion. Here is an excerpt:

    Each access point broadcasts at regular intervals (about ten times a second) a signal called a beacon, which gives information on its BSSID, its characteristics, and, if applicable, its ESSID. The ESSID is automatically broadcast by default, but it is possible (and recommended) to disable this option.

    Whenever a probe request is received, the access point checks the ESSID and the traffic volume request found in the beacon. If the given ESSID matches that of the access point, the access point sends a response containing synchronization data and information on its traffic load. This way, the station that receives the response can check the quality of the signal being sent by the access point in order to determine how far away it is. Generally speaking, the closer an access point is, the higher its data transfer capacity is.

         This implies any time a probe in the range of the Wi-Fi AP mode is received, it is examined to check for matching information. What if a flood of these happen? This could be the cause of the delays.

    Clem