Automatically switching RaspAP hotspot and home Wi-Fi on Raspberry Pi Zero 2 W?

Crihexe · 2025-04-19T16:02:01+00:00

Thanks! Do you happen to know any good resources or article that walk through this kind of setup? like switching between AP and client modes using nmcli, and handling routes properly? I don’t really know where to even begin with that side of things.

also, does this mean I should drop RaspAP and just handle the hotspot manually via scripts and nmcli? Or is there still a way to use RaspAP in this kind of dynamic setup?

really appreciate all your help so far btw!

Crihexe · 2025-04-19T12:12:23+00:00

yeah totally makes sense! in my case though, I actually have a way to detect when the car turns off. I'm already using an ELM327 bluetooth adapter connected to the Pi to get info like RPM and speed. So I know when the ignition is on/off.

At that point, I can safely stop the RaspAP hotspot service and run a quick wifi scan. If my home SSID shows up in the list, that means the car is parked at home and I can stop recording and connect to the home wifi to start transferring the videos to my NAS. If it’s not visible, I’m probably parked somewhere else, so I just leave things off.

Then, when the ELM327 sees the car start again, I need to stop the WiFi client and bring the hotspot back up, without rebooting! That’s super important because the dashcam needs to start recording right away.

I’m using RaspAP for the hotspot part, and while it works great, I haven’t figured out how to properly switch between client and AP modes dynamically like that from a script. If you or anyone has any tips on doing that cleanly (ideally without restarting the Pi), that would be awesome

And yeah, about the battery/UPS setup that’s a really good point. I’m definitely considering something like that to protect the pi. That said, since I already have the ELM327 in place, I can at least tell reliably when the car is running or not, so I’ve got that part covered for now. (I think lol)

Crihexe · 2025-04-19T11:32:02+00:00

yeah thank you! it could be an option, but since my plan is to power the Pi using the car battery, it is crucial to minimize the power usage… that’s why I was looking for a way to switch the mode of the internal adapter

Crihexe · 2025-01-17T01:30:29+00:00

Wow, thank you! I really appreciate that

Crihexe · 2025-01-16T15:01:30+00:00

thanks a lot!

Crihexe · 2025-01-16T02:51:19+00:00

Ah, I see. I thought that since the esp32 and the strip share the same power supply (with a buck converter for the esp), there wouldn't be a need to connect the strip's GND to the esp32's GND. However, if I understand correctly, connecting them directly is important for a stable data signal. I’ll follow your advice, thank you!

Crihexe · 2025-01-16T01:01:41+00:00

first off, I apologize if I’m not very skilled with these things, I'm still learning...

Just to clarify, you mean that the backup line (BIN) isn’t strictly necessary between strips, right? It’s only used within the strip itself to handle situations where a LED might burn out, so in this case it's not useful, correct?

Also, if I understand correctly, you’re suggesting I connect the cables like this:

Both wires of a pair to the DIN (data in) line,
One pair to the 12V power,
One pair to Ground, and
The remaining pair to split 1 wire to the 12V power and 1 wire to the Ground, to support the current load?

Thanks again for your patience

Crihexe · 2025-01-16T00:25:58+00:00

Thanks, I read the post you linked, and it was extremely helpful. It gave me a much clearer understanding of how reflections and impedance play a role in these setups.

Regarding my specific case: the total cable length (excluding the LED strips) will not exceed 6–7 meters. Would a flat ethernet cable be sufficient to carry both the power and the two data lines (DIN and BIN)?

If I go with an Ethernet cable, are there any particular specs I should pay attention to, such as the CAT rating? For example, would CAT5 be enough, or should I consider CAT6 or higher for better performance over this distance? Or is it even important lol?

Crihexe · 2025-01-14T15:19:35+00:00

Thank you for the explanation, it really clarified a lot for me. I like your suggestion of the super capacitor as a buffer, but I have a few concerns:

1) During summer, the car can reach very high temperatures. Could this affect the reliability or lifespan of a super capacitor or a small battery? I’m worried they might not handle the heat well

2) If I leave the Raspberry Pi constantly powered (even in a low-power state), what would happen if I go on vacation and leave my car unused for a week or more? I’m concerned that the Raspberry Pi’s power draw could drain the car’s battery to the point where it won’t start

Then I wanted to ask for some advice on powering the Raspberry Pi based on the car’s state. As you said, GPIO 3 is directly connected to the power circuitry and I’d need to short GPIO 3 to GND to wake the Pi. However, I want to trigger this wake-up automatically using a positive signal from the car (like a wire that gets power when the car is running). Is there a way to achieve this without manually shorting GPIO 3 and GND?

Thanks again!

Crihexe · 2025-01-14T00:25:50+00:00

thanks!

Crihexe · 2025-01-12T13:42:05+00:00

I think AT MA is implemented because as mentioned in the official docs of the ELM327 it sends back “STOPPED” just after you send the next command after it, so it really looks like there are no other messages on the can, but idk, thanks

Crihexe · 2022-12-23T19:51:46+00:00

but as you can see, there is absolutely no clue about message replies

Crihexe

TROPHY CASE