4 ms·

I read ATDT -- thought "Oh, the Hayes command to dial - wonder what it means now." Great story. Good memories. https://en.wikipedia.org/wiki/Hayes_command_se

by ghouse 8y ago

I read ATDT -- thought "Oh, the Hayes command to dial - wonder what it means now." Great story. Good memories. https://en.wikipedia.org/wiki/Hayes_command_set https://en.wikipedia.org/wiki/Hayes_command_set

jetrink 8y ago
That command set is still in use! I was working with it just last week to control an LTE module.
- illegalsmile 8y ago
  Absolutely! While it's not my preferred method of control, you can send AT commands encapsulated in SMS to update/troubleshoot BGAN terminals.
- jpm_sd 8y ago
  Iridium modems use it too!
  - clort 8y ago
    Its embedded into GSM modules; Phones need it to do anything, to check firmware versions, to send and retreive SMS messages, to make calls etc. I used it to control the 3G dongle I had (basically, a GSM module in a stick). Most times the device will act as a serial device.
- askvictor 8y ago
  Also used in the esp8266 when it's configured in wifi-serial mode.
- pooppaint 8y ago
  At commands are used for many nonmodem things too.. Bluetooth adapters, zigbee adapters, HC12 transceiver, other various proprietary devices tied to a UART in addition to LTE, GSM/GPRS (I guess technically some of those are modems but they’re pretty far removed from the original design)
- 3chelon 8y ago
  AT commands are still in use inside your smartphone. On an iPhone, when the main CPU wants communicate with the baseband chip to make a call or send SMS or whatever, it literally sends AT commands. In fact, one of the earliest iPhone jailbreak exploits relied on a vulnerability in the AT command interpreter inside the baseband.
  - kazinator 8y ago
    Commands that have to prefixed with AT are still in use. Most of the actual commands after the "AT" part are not recognizable to someone who knows dial-up modems; they have nothing to do with the Hayes set other than the AT prefix/misfeature.
    - 3chelon 8y ago
      Yeah, that's what always confused me about it when I worked on GSM phones back in the mid-2000s - if you're going to overload an old protocol so heavily, it's time for a new one.
      - emmelaich 8y ago
        Probably nostalgia! That would be good enough for me.
kazinator 8y ago
This irksome AT prefix is still jused in mobile modems, all the way up to LTE. You'd think they'd drop this "Simon Says" sequence once and for all from the commands; they would work just fine without it. Why can't I just type !GSTATUS instead of AT!GSTATUS? at!gstatus? !GSTATUS: Current Time: 555877 Temperature: 29 Modem Mitigate Level: 0 ModemProc Mitigate Level: 0 Reset Counter: 14 Mode: ONLINE System mode: LTE PS state: Attached [...] There should be an AT command to disable the AT prefix.
- merlincorey 8y ago
  The AT prefix is to get the ATtention of the /serial/ device, which modems almost always are in some respect. I don't know how much low level serial protocol programming you have done, but in my experience, there is possibility of random line noise, and such. This is why generally these low level protocols have both PREFIX and POSTFIX for commands. In the case of Hayes commands for modems, the prefix is AT, and the postfix is carriage return and line feed.
  - kazinator 8y ago
    > how much low level serial protocol programming you have done Tons! The AT prefix, as such, does nothing whatsoever for error detection or recovery. If we add an AT prefix to an N-character command, the possibility of corruption in the N-character command part is exactly the same as before. Now, the AT also has to be correctly received, too. An example of a textual protocol whose framing actually means something is the Mobitex MASC: http://www.mobitex.com/resources/masc/MASC_Guide.pdf http://www.mobitex.com/resources/masc/MASC_Guide.pdf MASC frames have a checksum and length field in addition to the framing (frames start with ^ and end with a CR). MASC also dictates the use of 7 bits with even parity; so parity checking is possible by both endpoints. Still, that leading is a fluff feature that contributes nothing; the protocol could work fine with frames just being sequences of non-CR characters terminated by CR. Modems usually have a solid connection to the host, often a short one; it's the actual end-to-end traffic that is susceptible to corruption; not so much the local commands between the host and modem. These modern LTE modem is often integrated onto the same chip as the host processor which is sending it the AT commands.

by ghouse 8y ago

jetrink 8y ago

That command set is still in use! I was working with it just last week to control an LTE module.

illegalsmile 8y ago
Absolutely! While it's not my preferred method of control, you can send AT commands encapsulated in SMS to update/troubleshoot BGAN terminals.
jpm_sd 8y ago
Iridium modems use it too!
- clort 8y ago
  Its embedded into GSM modules; Phones need it to do anything, to check firmware versions, to send and retreive SMS messages, to make calls etc. I used it to control the 3G dongle I had (basically, a GSM module in a stick). Most times the device will act as a serial device.
askvictor 8y ago
Also used in the esp8266 when it's configured in wifi-serial mode.
pooppaint 8y ago
At commands are used for many nonmodem things too.. Bluetooth adapters, zigbee adapters, HC12 transceiver, other various proprietary devices tied to a UART in addition to LTE, GSM/GPRS (I guess technically some of those are modems but they’re pretty far removed from the original design)
3chelon 8y ago
AT commands are still in use inside your smartphone. On an iPhone, when the main CPU wants communicate with the baseband chip to make a call or send SMS or whatever, it literally sends AT commands. In fact, one of the earliest iPhone jailbreak exploits relied on a vulnerability in the AT command interpreter inside the baseband.
- kazinator 8y ago
  Commands that have to prefixed with AT are still in use. Most of the actual commands after the "AT" part are not recognizable to someone who knows dial-up modems; they have nothing to do with the Hayes set other than the AT prefix/misfeature.
  - 3chelon 8y ago
    Yeah, that's what always confused me about it when I worked on GSM phones back in the mid-2000s - if you're going to overload an old protocol so heavily, it's time for a new one.
    - emmelaich 8y ago
      Probably nostalgia! That would be good enough for me.

kazinator 8y ago

This irksome AT prefix is still jused in mobile modems, all the way up to LTE. You'd think they'd drop this "Simon Says" sequence once and for all from the commands; they would work just fine without it. Why can't I just type !GSTATUS instead of AT!GSTATUS? at!gstatus? !GSTATUS: Current Time: 555877 Temperature: 29 Modem Mitigate Level: 0 ModemProc Mitigate Level: 0 Reset Counter: 14 Mode: ONLINE System mode: LTE PS state: Attached [...] There should be an AT command to disable the AT prefix.

merlincorey 8y ago
The AT prefix is to get the ATtention of the /serial/ device, which modems almost always are in some respect. I don't know how much low level serial protocol programming you have done, but in my experience, there is possibility of random line noise, and such. This is why generally these low level protocols have both PREFIX and POSTFIX for commands. In the case of Hayes commands for modems, the prefix is AT, and the postfix is carriage return and line feed.
- kazinator 8y ago
  > how much low level serial protocol programming you have done Tons! The AT prefix, as such, does nothing whatsoever for error detection or recovery. If we add an AT prefix to an N-character command, the possibility of corruption in the N-character command part is exactly the same as before. Now, the AT also has to be correctly received, too. An example of a textual protocol whose framing actually means something is the Mobitex MASC: http://www.mobitex.com/resources/masc/MASC_Guide.pdf http://www.mobitex.com/resources/masc/MASC_Guide.pdf MASC frames have a checksum and length field in addition to the framing (frames start with ^ and end with a CR). MASC also dictates the use of 7 bits with even parity; so parity checking is possible by both endpoints. Still, that leading is a fluff feature that contributes nothing; the protocol could work fine with frames just being sequences of non-CR characters terminated by CR. Modems usually have a solid connection to the host, often a short one; it's the actual end-to-end traffic that is susceptible to corruption; not so much the local commands between the host and modem. These modern LTE modem is often integrated onto the same chip as the host processor which is sending it the AT commands.