Telit HE910 Questions

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4 thoughts on “Telit HE910 Questions”

  1. Since 12.00.005 is not certified for use in North America.

    We have no choice but use 12.00.004 firmware for Telit HE910.

    Unfortunately, with 12.00.004 firmware,  AT#SERVINFO, AT#RFSTS, AT#MONI has problems reporting the signal strength when the cellular network is of type 3G. Verified in India with many 12.00.004 firmware running Telit HE910 devices. Looks 12.00.004 has real problems regarding that and fixed in 12.00.005. 
    ID#17110 Improvement MONI output
    reporting to avoid not valid data during a voice call
    ID#16875 Handling AT#RFSTS report during
    voice call     

    So, we switched to AT+CSQ to get signal strength.

     

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    Data : We read Telit_HE910_UE910_UL865_AT_Commands_Reference_Guide_r7.pdf and derived the following logic to get actual dBm from AT+CSQ output. 

    (CSQ_Output * 2) – 113
    Example  : If CSQ output is 26. Signal Strength in dBm is (26 * 2) -113 = -61 dBm ./ -60 dBm

    Question 1: Can the above logic be used for both 2G and 3G networks ? Because we are little confused as two different scaling mentioned for 3GPP TS25.133 and 3GPP TS27.007 in Telit AT document.  I am assuming all these are internally taken care and AT+CSQ output can be used for both 2G and 3G network as in above logic. Is that correct ?  If not, what would be the logic, to derive dBm from AT+CSQ output for 3G network ?

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    Data : With 2G network, below response for AT command responses are found.

     

    +COPS: 1,2,"40441",0
    +CSQ: 15,7
    #SERVINFO: 0,-79,AIRCEL,40441,73,0191,00,1,,I,01,0

    – Applying the logic for AT+CSQ Output ((15 * 2 ) -113) , we get  -83 dBm as signal strength.

    – Same time Same second, AT#SERVINFO reports -79 dBm. 

    – On multiple runs, we observed a difference of 4 – 6 dBm’s with respect to AT+CSQ and AT#SERVINFO. 

    – Network is 2G (Take a look at AT+COPS? output). 

    – Network doesn’t change in the process.

    Question 2 : Incorrect AT#SERVINFO behavior for 2G Networks as well (in 12.00.004 firmare) ?

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    Question 3 : Can we have information for below AT commands on what would be the maximum time to wait before we look for data from the Telit HE910 ?

     

    AT+CMGF=1

    AT+CNMI=2,1,0,0,0

    AT+CMGD=5,4

    AT#CCID

    AT#SERVINFO

    AT#CGSN

    AT#CIMI

    AT#CGMR

    AT+CGACT?

    AT$GPSP?

    AT+CSQ

     

    Earlier we assumed all the above commands takes a second or less to respond for Telit HE910. But, we observed AT#SERVINFO and AT$GPSP? at times takes more than a second, if we ran in loop continuously. Rather than programming our software to wait for a blind amount of delay, we would like to hear from you, what would be the maximum delay for each of the above AT Commands.
     ——————————————————————————————————————–
    Question 4 : Does response for above listed AT commands always contain either one of the two strings in it, "OK" or "ERROR" ?

                        Knowing this helps us to confirm that FULL response is received for the sent AT command in our software.

    Faster response for the questions would really help us deliver our software on time. As above mentioned Telit modem questions is the only blocker for us to release our software now. 

    Thanks

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    Question 5 : Random times, AT#SERVINFO reports "+CME ERROR : no network service". Is that acceptable behavior?
    Data : In 2 hours of continuous testing, 3 times, AT#SERVINFO response was
    +CME ERROR : no network service
    In our continuous testing, we send the following commands repeatedly AT#SERVINFO, AT+CGACT?, AT+CSQ and AT$GPSP.
    I also, wanted to let you know that, I have manually connected to this network using AT+COPS=1,2,"MCCMNC" and this is a network which most of the times has poor signal
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    1. Telit Technical Team

      Let me know if you are looking for any more, additional detail to answer the questions we have. I can help with that.

      Thanks 

      1. We have got answers for most of the questions from Telit America Technical Support Team

        Answer for Question 1:

        The logic you used (RSSI=2*CSQ_output-113) is correct for both 2G and 3G. It’s useful to keep in mind that each CSQ value corresponds to a dB range, not a strict value. In the example your provided,  CSQ=26 corresponds to an RSSI of -61dBm…-60dBm
        In addition to AT+COPS? (which is easy and direct) there are other ways to detect the "network mode" or the access technology of the registered network:
        1) The AT+CREG? command will indicate the network mode, but first you must set it to mode 2. In other words,
        a)
        AT+CREG=2 
        OK
        AT+CREG?
        +CREG: 2,1,"32C5","D050CF3",2
        The last parameter will indicate the network mode: 0=2G, 2=3G. Please refer to the HE910 AT command user guide for mode details (see pages 71,72). Please not that this will enable unsolicited registration messages from the network. To disable this, return to AT+CREG=0
        b) Another way to detect the PS network mode is using command AT#PSNT? For example:
        AT#PSNT?
        #PSNT: 0,3
        The last parameter indicates the network mode: 0=GPRS network; 1= EGPRS; 2=WCDMA; 3=HSDPA

        ———–———–———–———–———–———–———–———–———–———–———–
        Answer for Question 2 :

        The value reported by SERVINFO is not the RSSI. It is the RSCP (Received Signal Code Power). Using the AT#RFSTS command, which reports both RSSI and RSCP should demonstrate the difference:
        at+csq
        +CSQ: 16,2
        OK
        AT#RFSTS
        #RFSTS: "310 410",9766,203,-6.0,-81,-75,32C5,FD,-128,128,19,4,2,,D050CF6,"310410492095720","AT&T",3,0
        OK
        AT#SERVINFO
        #SERVINFO: 9766,-75,"AT&T","310410",203,32C5,128,3,-81,"II",FD
         
        For CSQ=16, RSSI=(2*16)-113= -81dBm
        Looking at the output of AT#RFSTS, the value in red is the RSSI, which is equivalent to the converted CSQ value. The value in blue in the AT#RFSTS output is the RSCP, which is equivalent to the value reported by SERVINFO
        ———–———–———–———–———–———–———–———–———–———————-
        Answer for Question 3 :

        Most commands will execute within 1-2 seconds, but this cannot always be guaranteed (as you have observed), for various reasons. Instead of adding fixed time delays, it would be advisable to wait for a response from the module before sending the next AT command. 
        Every command issued to the HE910 module returns a result response. The time needed to process each command and return the response will vary depending on the type of command type. Commands that do not interact with the SIM or the network, and only involve internal setups or readings, have an immediate response. However, there are cases when the module will take longer because of other operations taking place that are of higher priority than AT commands. 
        Commands that interact with the SIM or the network could take many seconds to send a response, depending on the network the command may interact with.
        For this reason, your application will be more robust by writing your script so that it waits for a response from the module before moving on to the next command.
        Appreciate TS-Americas!

        1. hi,

          regarding question nr.4 :

          you should find the answers in  3.2.  AT Command Syntax chapter  of HE910 AT commands reference guide.

           

          Regarding question nr.5:

          this could happen because  temporary fading can happen  between one command issuing and the next one, caused by many factors if you are in a real enviornment, especially if with a  network which most of the times has poor signal