This was my attempt to create a a SNES to Bluetooth adapter. It works but the average latency was 18.35ms, which I think is too much to be considered a good controller.
I have been contemplating making my own HOTAS since every time I have the cash to buy one, I either can’t find one or it gets cancelled midway through shipping and I get an automatic refund. I’m not sure where to start with that though…
How much are you doing with “rolling your own” vs using off the shelf solutions? For example if you are deep into rolling your own which Bluetooth profile are you using?
So in this case it’s my own code to read the state of the controller and using the ble-gamepad library, which uses NimBLE under the hood. There could be some optimizations but getting to be under 10ms probably is going to use a lot of time I could just be playing games.
So you suspect the latency (enough of it anyway) is introduced in your translation code? I absolutely understand not wanting to go to the nth degree for optimization when this is a hobby project. Could you throw hardware at it? Not all ESP32 run at the same speed. Perhaps buy an oversized one that will execute your underperforming code faster?
There probably could be some optimization in the translation, such as passing the controller object as a reference when checking the state of the buttons, rather than doing two loops to read the state and act on it. But I doubt that is the source of the largest latency since this is compiled to run at 240mhz (I did some additional testing at 80 as well, about the same results). I’m using a d1 mini off alliexpress so not the highest quality but I wouldn’t expect a huge performance hit.
Without more testing it’s hard to say. I don’t want say it’s the hardware without proof, but would require a much deeper dive into esp32 and c++ than I want to do right now.
It looks like 18.35ms is not really among the best, but there are still lots of products in that range.
I dunno if I’d say your project didn’t work out… Maybe more like you succeeded but still have work to do. Do you think you’ll try swapping the Bluetooth for a 2.4Ghz module or something and see if that performs better?
Hmm I was thinking maybe an old phone but that’s not that old.
Try charging while connecting. I’ve found that a low battery often seems like poor connection quality. The way it gives up when it can’t connect is very similar to just the battery dying.
It’s really hard to judge without additional testing, I’m always more likely to blame my code than hardware. My guess would be something in the stack, be it my code or the library that puts it above a frame but that kind of investigation is more than I want a hobby project to be.
I think the esp32 maximum throughput is 700 kbps, so you might be able to get a better performance.
I don’t have much experience with the esp32, but the first thing I would do is just a spoof program that sends simulated inputs, and see how’s the latency without any other functionalities.
That will give you a good idea if the problem is your code or the stack (its not infaillible though).
Yeah one approach is that BLE-Gamepad library supports gpio pins as button inputs, so in theory I could get a baseline of what the Bluetooth stack of the library is by soldering the jst connector to connect the Arduino (that triggers the button presses and measures the result from the Mister SNAC port).
Otherwise I’d basically have to develop my own controller code to port onto various Bluetooth stacks for testing, but that seems like more than I want to do right now.
I read that people who play a lot of FPV shooters have higher than average reaction and perception time. 18ms is ridiculously fast though, I’d be surprised if someone could consciously register it. I know gaming monitors market latency in the 1.5ms range, so maybe elite gamers can perceive the difference. Someone else pointed out that there are concerns over latency stacking between all of the devices, and that’s a really valid point.
18ms is okay but for a lot of retro content, it’s running 60fps. That means it’s one frame is 50/3ms, aka 16.6666ms. Sub 1 frame is good enough, 18ms is not in my opinion.
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