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My goal is to have a servo that can be controlled by a mouse "instantaneously", aka as fast as a racing video game cursor or limited by the speed of the servo itself.

So far, I have tried Bluetooth Low Energe (BLE), and I can get about 150ms "in practice" because I can't set the connection interval with the library I am using ("In the Hand BLE" for .NET). However the theoretical limit seems to be 7.5ms (according to this article).

With that said my questions are these:

  1. Is the theoretical 7.5ms speed for BLE "realistic" or am I better off using legacy Bluetooth or Wifi?
  2. If neither, is there something else I should be using for quickly sending wireless signals to the microcontroller controlling the servo? I.e. is this "solved" with some standard solution? I am using a Meadow F7 to receive the signal and a .NET core app to send it, but I can easily switch to Arduino / Pi / Python / whatever.
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2 Answers 2

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This question is not specific enough to get accurate answers.

Wifi has no guaranteed latency, e.g. this post mentions as a typical wifi latency a 50 percentile less than 4,5 ms, but worst case up to 1 second. It depends on your application whether that is acceptable or not.

There exist solutions for deterministic wireless communication, e.g. IO-Link wireless solution offers low latency of 5ms and synchronization rates of 10 microseconds, for up to 40 nodes (sensors or actuators). But this obviously comes at a higher cost than a wifi router.

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  • $\begingroup$ Thank you for the reply, I will read everything about the solution you linked. The discussion on the thread above is already helping me. (Can't upvote yet, need 15pts, sorry). $\endgroup$
    – Vincent S
    Dec 5, 2023 at 5:08
  • $\begingroup$ can I ask if you have a relationship with CoreTigo? Seems like it's a funded startup, it's a pain to even get started, and it's probably way oversold in terms of the advertisement not matching reality. Just got burned on Wildnerness Labs Meadow (C#-development Raspberry Pi competitor). Promises the world, but then can't read input pins faster than once every 150ms. $\endgroup$
    – Vincent S
    Dec 11, 2023 at 4:50
  • $\begingroup$ I am not affiliated to CoreTigo. If you are looking for a hobbyist solution, then I'd also have a look at what is being used in the drone / RC community, as they also need reliable data transfer. Also: it's not that wifi cannot work, but it depends: if you can assign a dedicated network with separate channel and avoid interference (e.g. from microwave oven or other networks) then it might work reliably enough. But if you are living in an appartment block surrounded by 15 neighbours, each running wifi routers and repeaters on 'auto channel', then don't bother... $\endgroup$
    – JRTG
    Dec 13, 2023 at 11:07
  • $\begingroup$ I really appreciate all the help @JRTG! $\endgroup$
    – Vincent S
    Dec 19, 2023 at 3:26
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Try WiFi: per this answer it's a fair amount faster than bluetooth, it's already widely available, and it's easy to implement socket-based approaches that will be as real-time as the operating system allows.

At some point this becomes a moot point, because most people and servos will be slower than most wireless connections, but regardless.

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  • $\begingroup$ This post mentions for a typical wifi latency a 50 percentile less than 4,5 ms, but worst case up to 1 second. For a hobby project this might not be an issue, but I don't think wifi can be considered a reliable solution for wireless servo control. Unless maybe if the remote has some logic to deal with this latency (e.g. setpoint interpolator, safety stop in case of excessive latency, etc). $\endgroup$
    – JRTG
    Nov 29, 2023 at 18:52
  • $\begingroup$ If you're exploring 'wireless' (which is the premise of the question) you've already abandoned connection reliability in favor of other factors. Any communication strategy will have potential QoS issues, this is not unique to wifi (and is certainly the case with bluetooth). $\endgroup$
    – cst0
    Nov 29, 2023 at 20:06
  • $\begingroup$ That is not correct. There even exist wireless control panels that provide an emergency stop button, i.e. a certified safety function over wireless. $\endgroup$
    – JRTG
    Nov 29, 2023 at 21:53
  • $\begingroup$ Wireless e-stops are not considered genuine e-stops (per OSHA, but YMMV in different countries), but still, making the choice to use wireless is absolutely a tradeoff (as is any engineering decision). But OP here is pretty clearly a hobbyist so I'm not super worried about it. $\endgroup$
    – cst0
    Nov 30, 2023 at 14:49
  • $\begingroup$ First: there are wireless e-stop solutions that are certified, both in the EU as well as in the US. See e.g. this article. But the point is: given the current context, concluding that wifi is the best option is presumptuous. A delay of 1 second might as well crash his setup. So at the least it is an incomplete answer. He'd need to take extra measures (separate network, fixed channels, ensure no interference, etc) and even then assess the risk in case of a big latency. $\endgroup$
    – JRTG
    Nov 30, 2023 at 18:04

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