Industrial Control Modem GSM
AT&Dn | Data Terminal Ready settings | |
&D0 | Modem ignores DTR | |
&D1 | Modem switches from data to command mode | |
| when DTR switches from ON to OFF | |
&D2 | Upon DTR switch from ON to OFF, the call is | |
| cleared down | |
AT+IFC | Defines if Flow Control is used between DTE and DCE. | |
| +IFC=0,0 | No flow control |
| +IFC=2,2 | RTS flow control (preferred) |
Flow control is the use of RS232 signals to start and stop the flow of data to avoid data loss during buffering. Check if your DTE supports RTS/CTS flow control (Hardware flow control). With Flow Control the DTE will send data to the DCE. The DCE will store this data in a buffer. When this buffer is full, the DCE will drop the
AT+IPR | Defines the Baud rate used for communications between the DTE and DCE. |
AT+IPR=0 | The Baud rate is selected automatically |
AT+IPR=9600 | The Baud rate is fixed at 9600 baud or another speed. |
| This is best left at its default setting of 0 (auto), unless your DTE demands |
| otherwise. |
AT+CBST | Defines the type of Bearer to be used. That is the communication between |
| the DCE and the GSM Network. |
AT+CBST=0,0,0 | Auto baud rate selection, transparent mode |
AT+CBST=0,0,1 | Auto baud rate selection, |
AT+CBST=7,0,0 | 9600 (V32) baud rate selected, transparent mode |
AT+CBST=4,0,1 | 2400 (V24bis) baud rate selected, |
Usually the baud rate is best left in the default Auto selection.
This ensures that the data transmitted first obtains a special acknowledgement signal from the receiver that informs the transmitter that the data has been received as transmitted and that the receiver is ready to receive the next set of data from the transmitter. If there is no such acknowledgement signal from the receiver, the networks will utilise their "data buffering" feature by using a special "forward correction" technique to ensure uninterrupted data transmission throughout.
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