Hacker News Reader

Comment by conradludgate | Hacker News Reader

I was recently looking into using some ESP32s to use on a BLE hardware project I am working on at the moment.

Although I do wonder whether wifi would be a better technology to use sometimes. The only thing I remember seeing is that wifi technology uses much more power.

From TFA it looks like WiFi 6 uses less power, is this true?

Anyone experienced have any suggestions whether BLE or WiFi would be better for streaming serial data from a device onto many platforms? (I currently have a BLE demo working, but working with Bluetooth stacks on mobile and desktop are a royal pain, network requests are very straightforward at this point)

View on HN

ESP-NOW might be suitable, as it requires less power than regular wifi.

From the docs:

“ESP-NOW is a kind of connectionless Wi-Fi communication protocol that is defined by Espressif. In ESP-NOW, application data is encapsulated in a vendor-specific action frame and then transmitted from one Wi-Fi device to another without connection.”

https://docs.espressif.com/projects/esp-idf/en/latest/esp32/...

Edit: this video discusses power consumption of esp now: https://youtu.be/6NsBN42B80Q

Sounds like a security nightmare.

What makes you say that?

One downside of using wifi if that devices like phones really don't like network connections that don't route to the internet. You sometimes have to fight them to stop the phone "helpfully" falling back to 4G or popping up all sorts of warnings about degraded networking to the user.

[edit]: This is assuming you are connecting directly to the device of course. Connecting the ESP32 to your existing wifi is well supported and much more reliable.

I have tried fighting this a couple of times but lost every time. Do you know a solution to make my Android phone keep the connection to a wifi without internet connection?

I lack a solution but would like to commiserate. We had some config errors on one of our VLANs, where DNS want reachable. The phones helpfully would just say no internet access and then bounce to 4g without any other sorry of error. What I would give to be able to just SSH into all these consumer services and just grep through the logs.

See https://github.com/leoleozhu/android-captive-portal and https://success.tanaza.com/s/article/How-Automatic-Detection...

If you could return valid internal DNS entries for these domains, and serve up a 204 to the right requests, you should be able to stay online.

You need to ensure you don't do it for every possible domain - I believe Chrome also tests random non-existent domains too, to ensure it gets back the expected error.

I have a "captive" or "promiscuous" dns server (it responds with its own IP for all requests) for my esp projects so this info is exactly what I need. Thanks a lot!

What about setting up some honeypot open-with-no-IP wifi hotspots near google HQ and near places where googlers are known to congregate (or in residential areas with high density of googlers working from home). Once it's their problem, they'll fix it pronto.

In my experience, I had no network until I answered "no internet connection, disconnect?" dialog that pops up in that case. Maybe you could also say "don't ask again". Then it was working fine.

What is not working fine though, is that I cannot access the internet through the mobile network at the same time. But this seems to really depend on the phone: it works on iPhones and on my previous Android phone, but not on a Pixel 5. I would like to download updates for the esp32 firmware through the mobile network, but this prevents it.

Chromecasts get initially configured by connecting your phone to a wifi network hosted by the device, so I wonder how Google makes that work.

Any idea how this works? Are they trying to connect to a particular address?

Yes, phones request a particular (plain http) URL from Google or Apple, which returns a 204 response. If they don't get a response, the network is assumed to have a connectivity issue. If they get redirected due to captive portal, they detect that and can prompt the user to log in.

https://github.com/leoleozhu/android-captive-portal

Sometimes as straightforward as pinging a server, sometimes elaborate as trying lists of random domains that some must respond and some must not resolve.

For equal target transfer rate and range, I don't think there would be a mode that any WiFi tech beats BLE in terms of using less power.

If power is your concern, have you considered nRF5 devices? Nordic has a proprietary profile for sending serial data over BLE (NUART) but AFAIK, you could only connect to one device at a time (not many).

Power isn't a huge concern, although it's a battery powered device, so having a longer battery life is a plus without needing to include a larger capacity battery.

I'll look into the nRF5. I've been using some of Nordic's code to test and build my prototypes already, although I feel like adding a proprietary profile on top will just make it harder to interface. Once I make the connection currently, all I need to do is enable notify on the specific characteristic which isn't too complicated (just a lot of code to actually get the characteristic)

This nrf52 demo might be salient:

https://youtu.be/tbl6Dui-_w4

https://github.com/NordicPlayground/nrf52-ble-multi-link-mul...

Reply on news.ycombinator.com