SEVENSTAX TCP/IP is an Internet protocol stack developed specifically for application in embedded systems. The SEVENSTAX TCP/IP-PPP variant allows transfer of IP packets via a serial interfaces. Theses interfaces are e.g. modems (analog, ISDN or GSM/GPRS/UMTS/LTE), UART/RS232 or serial connections via Bluetooth (SPP, DUN).

In addition to the Internet Protocol Version 4 (IPv4) all important protocols are included.

  • Internet Protocol Version 4 (IPv4) based on RFC 791

    • Subnet mask with CIDR blocks (Classless Inter-Domain Routing, RFC 1518 and RFC 1519)
    • IP fragmentation and reassembly according to RFC 791, RFC 815
    • Validation of IP address/subnet (RFC 3330)

  • Transmission Control Protocol (TCP) based on RFC 675, RFC793, RFC 1323

    • Checksum according to RFC 1071
    • TCP extensions according to RFC 1323
    • Error correction algorithms (RFC 1122)
    • Simultaneous operation in TCP server and TCP client mode
    • No limitation of simultaneous connections
    • Full frame size control (TCP segmentation according to RFC 879)
    • Sliding window technique (RFC 793)
    • Keep-alive packets (RFC 1122)
    • Protection against “Sequence Number Attacks” (RFC 1948)
    • Fast retransmission algorithm

  • User Datagram Protocol (UDP) based on RFC 768
  • Domain-Name-System (DNS) client based on RFC 1034, RFC 1035
  • Internet Control Message Protocol (ICMP) based on RFC 792

    • Sending ICMP host messages
    • Receiving ICMP host and router messages

  • Internet Group Management Protocol (IGMP)

    • Version 1 (RFC 1112)
    • Version 2 (RFC 2236)

  • (Simple) Network Time Protocol (NTP/SNTP) based on RFC 958, 4330

Point-to-Point Protocol (PPP)

PPP (Point-to-Point-Protocol)-Client and-Server based on RFC 1661 for Transmission of IP-packets uing serial interfaces:

  • 'On the fly' HDLC encoding/decoding (RFC 1662)
  • Configuration and connection establishment with
    LCP (Link Control Protocol)
  • Authentication using CHAP (RFC 1994) and PAP (RFC 1334)
  • Data compression with CCP (Compression Control Protocol)
  • IP-Configuration with IPCP (IP Control Protocol, RFC 1332)
  • IP-Header-Compression (Van Jacobson Compressed TCP/IP)
  • Protocol-Compression
  • Supports ACCM (Asynchronous Control Character Map)
  • automatic connection check (AutoPing)
  • PPP Identification-Message

Modem Connection Service

SEVENSTAX TCP/IP-PPP includes the SEVENSTAX Modem Connection Service (MCS). MCS is a module to monitor and control modems. A universal AT driver allows easy and fast connection of various modems (analogues, ISDN or GSM/GPRS/UMTS/LTE). SEVENSTAX MCS supports changing of the modems during runtime. Thereby, modems can be designed as changeable modules. Depending on the purpose a suitable modem can be inserted.

Features of SEVENSTAX MCS:

  • Extended AT command set
  • Extensive modem state machine
  • Error management upon broken connections
  • Monitoring of telephone numbers on call acceptance (PPP-dial-in)
  • Support of different modems with one firmware
  • Automatic identification of modems

For GSM/GPRS/UMTS/LTE modems the following additional functions are supported:

  • Request and set a PIN
  • Limitation of PIN requests (not supported by all modems)
  • Secret PIN: The PIN is generated by a secret function of the IMSI (International Mobile Subscriber Identity)
  • Scanning of signal strength
  • Sending and receiving of SMS
  • State machine for CSD and GPRS/UMTS/etc.
  • Permanent connection via GPRS/UMTS

Adaptations of the universal AT driver are available for numerous modems. We also offer adaptations to so far unsupported modems.


  • In-house development for embedded system
  • Minimal RAM/ROM usage
  • Zero-Copy
  • Simple API functions
  • ANSI-C source code
  • Works with and without RTOS
  • No "GPL contamination"
  • No royalties
  • MISRA checked

What you get

  • Well documented source code
  • User Manual
  • Software license

System Requirements

  • 32-bit timer/counter, accuracy: 1ms
  • ROM: inquire
  • RAM: inquire

License models