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Thierry Didi
Thierry Didi
Associate II
May 5, 2026
Solved

ST87M01 : MAX length of the data returned by AT#IPREAD

  • May 5, 2026
  • 3 replies
  • 196 views

Dear ST team,

In the ST87MXX AT Command User Manual, I can find that I can retrieve the data received on a socket with

AT#IPREAD:
AT#IPREAD=<context_id>,<socket_id>
#IPREAD: <context_id>,<socket_id>,<data_length>
<data>
OK

But I cannot find the max length of the <data> field that can be returned by the modem. 
Where could I find this information ?

Best Regards

Thierry

    Best answer by Didier HERROUIN

    Yes, AT#IPREAD is limited to 1 IP frame, it is a common way to proceed in NBIOT modems.

    And if there are more data to received, you will get an URC message so that the application can read them using again AT#IPREAD.

    Regards,

    Didier

    3 replies

    Didier HERROUIN
    Didier HERROUIN
    Technical Moderator
    May 7, 2026

    Hello Thierry Didi,

    The maximum size of an IP frame is defined using the AT command "AT#IPPARAMS", by the parameter "max_ip_frame_size"
    It can be set from 512 bytes minimum to 1600 bytes maximum.

    Best regards,

    In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question.
    Andrew Neil
    Andrew Neil
    Super User
    May 7, 2026

    So you're saying that the maximum amount returned by AT#IPREAD is one single IP frame?

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
      Thierry Didi
      Thierry DidiAuthor
      Associate II
      May 7, 2026

      Thanks Didier,
      I think that I have the same question as Andrew : Does it mean that IP#IPREAD never provides more than one IP frame ? (even if more data has been received by the modem) ?

      Then, in response to #IPRECV URC, we need to send several AT#IPREAD commands to read all the available data ?

      Best Regards
      Thierry

        Didier HERROUIN
        Didier HERROUINAnswer
        Technical Moderator
        May 7, 2026

        Yes, AT#IPREAD is limited to 1 IP frame, it is a common way to proceed in NBIOT modems.

        And if there are more data to received, you will get an URC message so that the application can read them using again AT#IPREAD.

        Regards,

        Didier

        In order to give better visibility on the answered topics, please click on 'Accept as Solution' on the reply which solved your issue or answered your question.
          Thierry Didi
          Thierry DidiAuthor
          Associate II
          May 7, 2026

          Super !

          many thanks !

          Thierry

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