Creating small WiFi network

  • Good day ladies and gentlemen
    I'm here with a probably noobie question so please take it into account :)
    There is a necessity to create an independent WiFi network which should do the following:
    each of 3 Pycom boards in the network connected to separate MCUs via UART. Those MCUs send data to Pycom board sporadically/regularly and the moment it receives the data it must be transmitted through Wi-Fi to all other boards for further processing. The devices will be in a circle of 100 m in diameter.

    I'm kindly asking to clarify such points to me:

    • for such a task, any of Pycom board will do the job cause each of them has WiFi and UART or there is some difference in the WiFi implementation (different ESP?) on different boards?
    • can such network work independently? I mean boards can talk to each other without a common WiFi router right? Or at least one board should be as a master/host?
    • for energy saving the UART messages can be processed via interrupt and not the constant monitoring of the line?
    • what I can expect in terms of latency of such communication?

    I choose to stick with the Pycom ecosystem because it seems to be the fastest to prototype such ideas so what is the starting point and following steps to implement such a solution in the Pycom environment?

    Many thanks for any thoughts

  • @jcaron many thanks for bringing more clarity, but even with good answers more questions appears :)

    • the solution with one AP can work for the first stage but the goal is to be independent of the accident shut down of any node. I mean if the main AP is corrupted would it be possible to dynamically switch this role to another active node or is there any possibility to have kind of mash network were all nodes are equal and can retransmit the data to all visible nodes?

    • regarding the environment, most of the use-cases are an industrial plant with not so many walls - most likely there will be a visible path between nodes but something more crowded is also possible. So what about claimed 1km range of Wi-Fi and opportunity of antenna connection? I'm ordering the FiPy for some future exploration of IoT and there is an onboard antenna that can be resoldered to something more powerful or how?

    • about the latency, 20ms will be great but even 50ms will do the job and maybe it's ambiguous but it must be combined with guaranteed delivery

    • regarding all this information maybe it will be better to focus on LTE Cat M1? Because I'm basically in the research stage of what can do the job better, the overall data throughput will be at most 1MB

    And I'm I understanding tight that the Pycom development environment will provide easy switch between WiFi/LTE Cat M1 in terms of coding?


  • @dnbrk

    • All Pycom dev boards should be the same in this respect. A WiPy should be enough.

    • You would indeed probably set one up as an AP while the others would be stations. However that means that all stations must be within reach of the AP. What's the environment? 100 m indoors is most probably impossible using Wi-Fi. Outdoors it will depend on many factors, including the types of antennas used, any obstacles, interference, etc.

    • If you want to be able to receive messages, then the devices need to remain active. That, coupled with Wi-Fi, means pretty high battery usage. Depending on what you do exactly, I'd think an average power draw of 100 mA is probably the right ballpark, which means a few dozens hours of runtime max. What's your use case?

    • What are your constraints in terms of latency? It should most probably be on the order of 10 ms or less, but it may depend a lot on many parameters (including the amount of data, the speed of your UART link, the Wi-Fi speed, which in turns depends on distance, etc.).

    Do you need guaranteed delivery (at the expense of latency if there's packet loss), or is latency more important (at the expense of lost data)?

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