this post was submitted on 12 Mar 2024
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Not All Projects Work Out (lemmy.world)
submitted 8 months ago by v1605@lemmy.world to c/retrogaming@lemmy.world
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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.

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[–] thanks_shakey_snake@lemmy.ca 29 points 8 months ago (2 children)

If anyone else was wondering, I found this neat data table of controller latencies to compare:

https://rpubs.com/misteraddons/inputlatency

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?

[–] lectricleopard@lemmy.world 9 points 8 months ago (3 children)

I use an 8bitdo sn30 pro. Apparently I haven't been using a good controller. Fooled me!

[–] v1605@lemmy.world 8 points 8 months ago

I wouldn't call that controller bad, just not optimal. For this, I would want to have it be under 10ms to publish the code and instructions.

[–] Splatterphace@lemm.ee 4 points 8 months ago (1 children)

I've had a lot of connection issues with that model

[–] lectricleopard@lemmy.world 3 points 8 months ago (1 children)

How so? It disconnects? Or won't connect to start?

[–] Splatterphace@lemm.ee 1 points 8 months ago (1 children)

Both, and I was literally right next to my phone

[–] lectricleopard@lemmy.world 1 points 8 months ago (1 children)

What phone do you have?

[–] Splatterphace@lemm.ee 1 points 8 months ago (1 children)

Samsung A53

[–] lectricleopard@lemmy.world 2 points 8 months ago

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.

[–] thanks_shakey_snake@lemmy.ca 3 points 8 months ago (1 children)

I have two of em-- They're pretty good! Definitely not perceptibly laggy or anything, at least to me.

Probably just outed myself as a casual.

[–] lectricleopard@lemmy.world 3 points 8 months ago

Casuals unite! Fuck it I'm just trying to have fun lol!

[–] v1605@lemmy.world 4 points 8 months ago (1 children)

It definitely could but the idea was to use only an esp32 rather than incorporating additional hardware.

[–] thanks_shakey_snake@lemmy.ca 3 points 8 months ago (1 children)

Yeah, I get that. Do you have any sense of whether that's a limitation of the ESP32, or with your implementation?

[–] v1605@lemmy.world 3 points 8 months ago (1 children)

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.

[–] Croquette@sh.itjust.works 3 points 8 months ago (1 children)

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).

[–] v1605@lemmy.world 3 points 8 months ago

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.

[–] TheEntity@kbin.social 9 points 8 months ago

Whether it works or not, this looks incredibly fun! That's a win in my book.

[–] Mr_Blott@lemmy.world 9 points 8 months ago

The project equivalent of your mum sticking your drawings to the fridge 😊

Hey, you tried, most wouldn't bother. You're the top 1% of humans in that way

[–] partial_accumen@lemmy.world 6 points 8 months ago (1 children)

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?

[–] v1605@lemmy.world 9 points 8 months ago (1 children)

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.

[–] partial_accumen@lemmy.world 6 points 8 months ago (1 children)

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?

[–] v1605@lemmy.world 3 points 8 months ago (1 children)

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.

[–] partial_accumen@lemmy.world 2 points 8 months ago (1 children)

Where do you think the (the majority of the) latency is being introduced?

[–] v1605@lemmy.world 1 points 8 months ago

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.

[–] Kolanaki@yiffit.net 5 points 8 months ago

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...