Today I Learned: Cell Phone Hot Spots are Also Routers

When I started down the road of putting a Raspberry Pico-W in charge of the Morse code key and on/off switch on our 20 meter rock-locked, QRP CW rig, Project TouCans, last year, I came across many, many microPython code examples where the entire point was to WiFi connect your Pico-W to your home router and then access it from other devices.

KO6BTY and I however, mostly use Project TouCans while out camping for POTA/SOTA. Consequently, the 'home router' route, (pun intended), didn't seem helpful. Ultimately, I found code example for setting up a Pico-W as a network as an access point as opposed to a client. That worked. We were able to WiFi connect a laptop to Project TouCans to turn the rig on and off and send either auto-keyed or straight key CW. It did however, lock whichever device into TouCans exclusively. That wasn't too big of a problem though, because I could make POTA self-spots and check out our signal on various SDRs using my smart phone.

Then, yesterday, as an indirect result of all the striaght key work of late, I wondered if a smarth phone could serve as a router. It turns out that that is exactly what the phone's hotspot is! I made a quick change to the code on the Pico-W and had TouCans up and running on one side of the phone's hot spot in under an hour. I was then able to attach my Chromebook to the same hotspot and control TouCans! And! I was also able to still see the internet on the Chromebook. This has turned out to be pretty cool. I'll talk about why as I document the new TouCans Web Control Panel in a follow-on post.

To talk to TouCans, or whatever you're favorite device might be, you need ot know the address of the device on your phone's hotspot. With my Galaxy S23, this turned out to be easy. I assume it is with most Android phones. The trick is to click into the hotspot icon, and then drill down to the 'attached devices' page. Click onn the label for the Pico-W, (in our case), then, click on the i-in-a-cirle info button. You'll be rewarded with the IP address of your Pico-W. You can then access the Pico-W from other devices using Python, JavaScript, or the network enabled programming language of your choice.

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