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31

One seldom-appreciated detail about "AT" commands is that many modems would start out in "auto-baud/auto-parity" mode. Initially, the modem would start out not trying to actually decode any serial data, but would simply watch for a consecutive low pulse and high pulse whose widths matched the same valid bit period (e.g. 3.333ms for 300 baud, 833us for 1200 ...


27

brhans is correct - Legacy. In the 1980s, Hayes began making the "Smartmodem 1200". It was obsolete almost immediately and Hayes rushed out the Smartmodem 2400. In that rush, there was no time for design alterations between the modem designs. As a result, Hayes were the first to make two different speed modems that accepted the same programming commands! ...


22

It refers to the Hayes command set which has been the standard for a long time for issuing commands to modems (and other equipment) over a serial line. Instead of the commands and data having two separate lines, only one line is used and to switch into command mode from data a certain sequence is sent, e.g. +++ followed by a set length pause. Then the ...


20

You're talking only about the downsides of the command set. Consider the upsides: By using the AT command set, your communication device can immediately be put on any IP network via the OS's PPP implementation. The alternative is that in addition to designing a custom protocol interface, you have to write your own network device driver for every OS you want ...


14

I'll expand on the other side of the question ... why not just add another signalling line to the interface? That can only be asked by someone who didn't live through all the permutations of signalling lines on a genuine 25-pin RS232 interface. In addition to TXD, RXD and Gnd, there were several other pairs of signals already, RTS/CTS (Ready to Send, Clear ...


13

The "AT" command set was to solve a problem of needing out of band control information over the same byte-stream channel arbitrary data was sent. This was a common problem of modems, back when they were external boxes connected to computers via a serial cable. Hayes was a manufacturer of such modems, and gained a lot of early popularity. Their solution ...


10

After much googling and mashing together various answers, I got it working. Here's the AT command sequence. You can test this from start to finish, you'll just need to confirm the APN of the carrier you're using. // My comments are here Command to send is here Expected responses are here // See if the SIM900 is ready AT ...


9

The first Hayes modem to use "AT" commands chose "A" as the first character of its command prefix because it needed to support multiple baud rates, and the "A" on the line looks like: -------_-_____-x---------- which has a 5:1 ratio between the longest and shortest 'low' times (the "x" may be high or low depending upon parity settings). No rate slower than ...


7

I have used the following command: AT+CCLK? which returns the date and time, like: +CCLK: "00/01/12,05:44:53+00" successfully in products using three different cell modules: Enfora, Telit, and Sierra. The fact that it uses a + character after the AT implies it is a common (as opposed to proprietary) command, and should be available on most if not all ...


6

The answer is in the HC-05 documentation: you have to make sure the Key34 is connected to Vcc when sending some AT Commands. simply hold your button down while pressing ENTER in your terminal. http://www.instructables.com/files/orig/FKY/Z0UT/HX7OYY7I/FKYZ0UTHX7OYY7I.pdf


6

Yes, you can use a delay and ignore the response, but if it is a response to sending the actual SMS itself, then that could take some time. You would have to send several SMS messages by hand to judge how long it might take the OK to come back, and then add on some margin to the longest delay seen. It would be much better to actually look for the OK ...


4

I found one way by which escape character can be sent... You do this by specifying the length to AT+CIPSEND command. So the commands exits only after you have sent all data specified by the length... AT+CIPSEND=12 By doing it this way... the escape character can be sent..


4

Okay, I was heading down dead ends there. The vendor just confirmed that there is a fault with the SIM card holder on the board.


4

First of all, NITZ is poorly supported in many networks (can you say COST-CUTTING). I would not rely on it at all as 1 in 10 networks use it, especially in far flung places. Secondly +CCLK command is for the internal RTC of the modem. Some modems have facilities to update this clock from the network. Relying on this is risky. The above HTTP request is ...


4

AT+CLTS=1 ( Get local time stamp ) AT&W ( Save configuration ) Turn off modem and turn on modem(reboot to get local time from network) Next time when modem boots up you should be able to get local time by network and can be read by sending AT+CCLK? This worked for me i m using SIM800 GSM modem read AT command descriptions for more information


4

I'm actually also working on a SIM900 and had the same problem. One possible cause of the problem is that the SIM900 already has made a connection. Try re-starting the sim900 before issuing the commands. Also I set the APN settings with the AT+CSTT= command Below the in/output of my serial connection: For testing purposes use this. Be sure to have the ...


4

Solution is to reflash SIM900A with SIM900 software and it works like a charm. Here is the page that shows the solution. Flashing is no trickery, just a right sequence of operations, there is detailed instruction for arduino-like approach, my way required just a few major steps: Power up your SIM900A module to respond to AT commands in auto-...


4

All GSM modems that I know of have two modes: command and data. And that includes the SIM900. The modem starts out in command mode, where it is listening for AT commands, typically over a serial UART connection with a microcontroller. AT commands are patterned after the Hayes telephone modems of the 1980s and 90s. AT stands for Attention. They are used ...


3

PuTTY: AT+COPS=2 OK AT+CTZU=1 OK AT+COPS=0 OK +CTZU: "15/05/06,17:25:42",-12,0 Works perfectly, after that you have to parse the result and place in clk because this does not happen automatically. (at least in my Cinterion)


3

On the cellular modems I have worked, the voice path was set up by default to interface to a microphone and speaker. However most had a separate PCM interface which allowed the cellular modem to be connected to a Bluetooth headset via a Bluetooth module, provided it had a compatible PCM interface. According to this website, the format is typically a 64 kb/...


3

After extending the initialization string of the GSM modem with 'AT+CSNS=4' the device was able to connect with analog modems.


3

Thanks for all your help. The solution was modify the line ending option at the bottom of the Arduino serial console to send both CR and LF. Still not got PuTTY configured but have something to test now. Thanks :)


3

I recently started "playing" with this module, and there are a few things to keep in mind: the module base baud rate is 115200, don´t waste your time on 9600 it requires CR+LF to accept commands read the documentations (http://bbs.espressif.com/viewtopic.php?f=67&t=225) experiment with more than one tool, like Arduino IDE and Esplorer also check the ...


3

I solved the problem. :) The problem was with Extra "Space" in header. sprintf(DataToSend, "GET %s HTTP/1.1\r\n Host: %s\r\n\r\n", PATH, HOST); I removed that space: sprintf(DataToSend, "GET %s HTTP/1.1\r\nHost: %s\r\n\r\n", PATH, HOST); and then problem get resolved. here is the response from server: HTTP/1.1 200 OK Date: Fri, 19 Jun 2015 03:38:14 GMT ...


3

According to the manual, section 5.1.6.10.9. Send mail with attachment - #SMTPCL: AT#SMTPCL=<da>,<subj>,<att>[,<filename>,<encod>] This command permits to send an email with different types of attachments if GPRS context has already been activated (#SGACT or #GPRS). After sending message body text (as with #EMAILD),...


3

As @PlasmaHH suggested, changing the text mode to PDU mode (using AT+CMGF=0) did give me some more information. The parsed PDU string now contains a property udh which has some more information about the message. If it's a message consisting out of multiple messages it will tell me how many parts there are and what part this message is of the total message. ...


3

I got some help from an Aeris engineer with this one. It turns out that when a SIM first registers with the network, it requires better signal quality than subsequent registrations. When the SIM has successfully registered with the network the first time, some information is stored on the SIM that allows it to register easier the next time. Mobile phones ...


2

In principle an GPRS modem can listen to a socket for incoming connections but there are a few problems in practice: Most network providers don't give you an externally routable IP address and if they do they are often firewalled. Depending on the provider getting a routable address may be a free option, a paid extra or not available at all. If you get a ...


2

I figured it out. The modem had hardware flow control enabled by default. So I had to put it into null modem state. Its just a matter of shorting CTS and RTS lines each other. Now its working perfectly fine.


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