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>> "IoT devices still speak RS-232" > This is actually dangerously untrue! They very much do. Maybe you are thinking of modern low voltage devices? Where yea

>> "IoT devices still speak RS-232" > This is actually dangerously untrue! They very much do. Maybe you are thinking of modern low voltage devices? Where yeah you do not use that as much. But modbus and rs485/rs232 are very much alive in the industrial world where IoT is quite alive. > But modern modems aren't connected over serial. They are. Just not necessarily what you consider RS232. Usually when I did this a few years ago it was USB lines. Which is a serial bus. The AT commands are still used in pretty much all modems. Which you have in your pocket. That is how the cell modem sets up the call to the phone network. The venerable ATDT is still used all the time to setup the call to the network. The AT command set was for setting up the call and controlling aspects of the call (like max speed and protocols you allow). The auto negotiation is one layer out at the network/modem level. With older modems they had a speaker that let you hear it. It was that distinct tweeting with a buzz with a fade out. You just no longer hear it. AT did not do that at all other than kick off the process and setup the registers for the modem to know what to do at the negotiation step which is defined in the spec. Still all there.

mjg59 3y ago
Yes, the AT command set is used in modern modems. But they didn't choose to use it because of the line speed synchronisation properties. (Edit: and while the AT command set is supported, modern systems tend to use custom command sets in preference. For instance, Qualcomm modems support QMI which provides a binary interface to the modem and modern phones will tend to use that in preference)
atoav 3y ago
Electronics guy here. There are devices that speak actual RS-232 with e.g. -3 and 15V as logic levels. And there are devices that also say "RS-232" on their port, but expect logic levels of say 0 and 3.3V (or 5V). When you use one with the other any number of things can happen, including the destruction of the target microcontroller if the circuit is unprotected (most MCUs dislike sufficiently negative voltages on their ports). Now if we talk about servers or expensive media gear their RS-232 connectors are very likely top notch (and still very much present as you rightly noticed). Cheap devices are more questionable here.
- sumtechguy 3y ago
  With some devices 'rs232' seems more like a guideline than a spec sometimes :)
  - atoav 3y ago
    Exactly. Sometimes my feeling is that some manufacturers just think RS-232 is the name of the connector.

mjg59 3y ago

Yes, the AT command set is used in modern modems. But they didn't choose to use it because of the line speed synchronisation properties. (Edit: and while the AT command set is supported, modern systems tend to use custom command sets in preference. For instance, Qualcomm modems support QMI which provides a binary interface to the modem and modern phones will tend to use that in preference)

atoav 3y ago

Electronics guy here. There are devices that speak actual RS-232 with e.g. -3 and 15V as logic levels. And there are devices that also say "RS-232" on their port, but expect logic levels of say 0 and 3.3V (or 5V). When you use one with the other any number of things can happen, including the destruction of the target microcontroller if the circuit is unprotected (most MCUs dislike sufficiently negative voltages on their ports). Now if we talk about servers or expensive media gear their RS-232 connectors are very likely top notch (and still very much present as you rightly noticed). Cheap devices are more questionable here.

sumtechguy 3y ago
With some devices 'rs232' seems more like a guideline than a spec sometimes :)
- atoav 3y ago
  Exactly. Sometimes my feeling is that some manufacturers just think RS-232 is the name of the connector.