New Part Day: The $15 ESP32 With Cellular

Cruise around AliExpress for long enough and you’ll find some interesting new hardware. The latest is the TTGO T-Call, an ESP32 breakout board that also has a cellular modem. Yes, it’s only a 2G modem, but that still works in a lot of places, and the whole thing is $15.

On board the TTGO T-Cal is the ESP-WROVER-B, the same module you all know and love that features a dual-core ESP running at 240 MHz with 4 MB of Flash and 8 MB of SRAM. Add to this WiFi and Bluetooth, and you have a capable microcontroller platform. Of note is that this board includes a USB-C port, ostensibly wired so that it behaves like a normal USB micro port. That’s neat, 2019 is the year USB C connectors became cheaper than USB micro connectors.

In addition to the ESP32 module, there’s also cellular in the form of a SIM800 module. This module has been around for a while and used in many, many cellular-connected projects and products like the ZeroPhone. This module is only a 2G module, and that’ll be going away shortly (if not already) in built-up areas, but this can serve as a building block for modules that have more Gees than a 2G module. That said, if you’re looking for a WiFi and cellular bridge for fifteen bucks, you could do a lot worse for a lot more money.

49 thoughts on “New Part Day: The $15 ESP32 With Cellular

    1. Not sure about Europe but pretty much the rest of the world still has 2G/3G overlaid. We were trying to do some remote monitoring in Botswana and coverage was 2G > 3G > 4G as far as availability. We were thankful our devices had 2G fall back from their normal 3G as LTE modems would not have worked there. Dont quote me but the US is the only place I know that 2G (and 3G) are going away any time soon and that is out in 2022 (though adding a new device is nigh on impossible now).

      1. Depends on whom in Europe, but Vodafone has said publically they wont turn off until at least 2025.
        There are an awful lot of critical infrastructure devices in the UK running on 2g. The costs to change that at the client end of the network are huge.
        There will be support at government level to keep at least one 2g network running for a decade if not more.

        1. Oh. Great. I hadn’t heard that and we have some stuff over there on 3G. Now we have to scramble 4G devices over there which will be expensive (im in the US). Thanks for the heads up as I will start to investigate.

        2. BeiDou is coming….
          OK we are still waitiing for it, but one of the things it was supposed to be doing was supplying free or super low cost small data packets. I guess around the size of SMS
          Thus getting around the problem of having cellular connections for all IoT devices .

          But looks like it wont be ready in time for tehe 2g swtich off start.

      2. 2G on AT&T towers in USA are gone, there might be some equipment on leased towers but that should be gone by the end of the year. There is no room in tower shacks and no reason to keep equipment turned on.

    2. Hi Arjan,

      It’s been a while, but here in New York I ran on Ting, which uses T-Mobile 2G. It was spotty, but usable for me. There are maps available if you hunt, but don’t recall specifics. I had toyed with a few different providers, and they each have strengths and weaknesses. Your choice will depend mostly on your usage. I remember that T-Mobile was building out 2G as others discontinued, so they dominated IoT network offerings. Note this experience dates back to 2017

  1. I presume a 2G module requires a cellular plan of some sort. I would think that the cost of the module is irrelevant compared to the likely cost of a cell plan. How much does a cell plan cost and what carriers have such plans?

      1. There are no GSM bands in 2.4GHz, and while you can easily tune down basestations’ TX as they always use external antennas, handsets has no reason to be equipped with a mode to follow ISM band regulations and therefore such system can often only operate illegally. One way I can imagine is if someone is to buy a disused shopping mall and have it certified as a giant R&D radio anechoic chamber, then the “tests” conducted inside would be bound by radio regulations to a much lesser degree.

    1. From what I looked at a while ago, you’re looking at about $10 a month min. You can buy a certain number of minutes/data, but they usually expire after a month or a year. Either way, it works out to about $10/mo even if you transfer no data, but usually equates to about 1Gb of data.

    2. There are plans that offer exorbitant price per bandwidth and in return allows near-indefinite contract at cheap prices, intended for M2M or travellers. Things like few dollars per hundreds of kilobytes plus few bucks maintenance fee for couple years. Enough to see which vending machine needs how many cans of soda today.

  2. From someone who’s built an arduino phone by stacking a Sim900 shield onto an Uno, and topping it off with an I2C LCD 16×2, running off a 7.2v LiPo, I recognize the leap here. But why the sim800? Old surplus stock perhaps. On balance it does blow away my hardware specs. I’m sure the sd slot is not far behind. Looking fwd to my next build.

    1. Don’t believe it, that’s just the default firmware . . . .

      I seriously doubt that there is any technical reason that the ESP cannot operate in client mode if desired. So, just write your own firmware that does what you want.

    1. Yes, the 2G Wikipedia article is wrong when saying it will end in 2020. But several providers in Netherlands indeed will drop 2G except KPN. KPN Will keep it for now and in fact will drop 3G

  3. No more 2g in Canada. :,(
    actually, let me rephrase, no new 2g simcards in Canada. There are still some legacy networks in operation but they are being shuttered and shedding devices.

    1. My S3 and S4, I have a 3G picocell in my house and they both refused to connect to it when in auto mode, instead giving me 4g no bars or “no service” but would never see the full signal picocell unless I put them into 3G mode.
      Utterly stupid.

  4. Does anyone know a good 3g module for diy projects?, the major celular network carrier in méxico is already disabling 2g support in some areas, which i happen to be and i’m out of luck with my sim800 modules.

    1. Honestly if you are considering the future and have access to it the lower side LTE does just as well. The only thing that we have noticed is a small decrease in signal range. My company is using the Nimbelink pre certified (in the US) module nl-sw-lte-qbg96 with the Quectel BG96. Single antenna and does pretty well for us.

  5. Likely these are so cheap because 2g is disappearing. Someone is dumping these 2g only modules on the market for probably next to nothing because no one wants to buy them. Anyone deploying anything new and cellular these days is probably using 3g modules at a minimum if not lte. Both are likely capable of falling back to 2g networks as well.

  6. I just had to tack a cellular modem to an esp32 as part of a down detection system for a piece of industrial equipment that had to detect a common self shutdown and power outages
    This would have saved some soldering
    2g systems do still exist and are dirt cheap but the module I used can be 3g with a SIM swap if need be, would be nice if this was too

  7. Looks like as of December 31 this year the only remaining 2g network in the US will be TMobile and that’s going poof sometime next year. I don’t see it making sense to develop any 2G application in the United States unless there is already a suitable drop in replacement device that makes use of LTE.

  8. I have an Arduino 2g device with a Ting SIM card in the Midwest US. Just this year I started noticing spotty coverage, with large gaps. Looks like, at least with Ting, new activations are not allowed.

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