Circuit Switched Data (CSD) Setting

Applicable Products

Part number	Description
ZETA-GEP-LTE4 (EU)	Low Power LTE Cat 4 European Modem with GPIO and GNSS
ZETA-G-GPRS	Entry Level GPRS Modem with GNSS (GL)
ZETA-N2-GPRS	Entry Level GPRS Modem (GL)
ZETA-NEP-LTE4 (EU)	Low Power LTE Cat 4 European Modem with GPIO
ZETA-NLP-LTE1 (EU)	Ultra Low Power European LTE Cat 1 Modem
ZETA-N-LTE (EU)	High Performance LTE Cat 4 Modem with GPIO
ZETA-NSP-LTE1 (EU)	Low Power European LTE Cat 1 Modem

Objective

Circuit Switched Data (CSD) is a method of transmitting information between two wireless systems by circuit switching, rather than packet switching. This Application Note details how an analogue CSD can be achieved using two Siretta Zeta modems. The modems at either end are connected to a remote system at one end and a server at the other. The information can be in the form of data update or for monitoring purposes.

Solution

Requirements

• CSD enabled sim card with separate data number.
• Terminal emulator such as Tera Term / Hyper Terminal or Putty for modem configurations using AT commands.
• Siretta Modem Evaluation Kit (all Siretta ZETA modems can be used for CSD)
• Analog modem.
• RS232 to USB cable/ RS232 to RS232 cable.
• Working telephone line for analogue modem.

Note: All Siretta Zeta modems with the GSM/GPRS and 3G/UMTS capability can be used for CSD.

Device Setup

1. Connect the Siretta Modem to the PC using the supplied RS232 to USB cable.
2. Open Tera Term or terminal emulator of your choice.
3. Configure the COM port with the following settings for Siretta modems which support CSD.
   1. Bits per second: 115200
   2. Data bits: 8
   3. Parity: None
   4. Stop bits: 1
   5. Flow control: Hardware.
4. Open your terminal emulator on a PC that is attached to Siretta Modem and configure the Siretta modem using the following AT commands:

a) AT#DIALMODE=2
b) AT+FCLASS=0
c) AT+CRC=1
d) AT&K0
e) ATS0=1

COM3 – Tera Term VT

File    Edit     Setup     Control     Window     Help

AT#DIALMODE=2 OK AT+FCLASS=0 OK AT+CRC=1 OK AT&K0 OK ATS0=1 OK

5. Open the terminal emulator on the PC that is attached to the Analogue Modem and configure com port as step 4.
6. Dial the Siretta modem using the ATD command followed by data number (ATDxxxxxxxxxx).
7. While dialling is performed from the analogue modem you will see “+CRING: REL ASYNC” on the terminal window connected to the Siretta Modem indicating an incoming data call.
8. After one ring a connection will be established between the analogue modem and the Siretta modem. You can set the number of rings to any value by altering value of ATS0=n, where n = 1,2,3,4 etc on the Siretta modem side.
9. Both terminal windows will indicate that a CSD call has been established and any data sent from the analogue modem will appear at the Siretta Modem and vice versa.

System Integration

Once you have tested the connection you can replace the terminal emulator attached to the Siretta Modem with your remote system and then use the same method on the analogue modem to obtain data from your equipment using CSD dialup data call.

Additional Reading

Description	Author
AT command manual	Telit
Modem Starter Kit- Quick Start Guide: ZETA-xxP Quick Start Guide	Siretta