Useful links:
Before you discuss information described in this article with client, make sure that NDA is signed.
This article describes how to create SMS via GPRS command according to our protocol, chapter "3.2.8 Command 7/108 – SMS via GPRS".
For demonstration, we will convert gsminfo SMS to GPRS command with SMS password in device configuration set to "summer".
Convert SMS text to HEX to get Payload of this command.
Note: If password is set in device CFG, it must be included in SMS/GPRS command.
3. Add command ID "6C" at the begging of the Payload:
6C 73 75 6d 6d 65 72 20 67 73 6d 69 6e 66 6f
4. Calculate how many bytes Command ID + Payload has to find out what is Packet length:
In total there are 15 bytes.
5. To get Packet length of GPRS command we need to convert total number of bytes, in our case 15, from DEC to HEX:
6. Packet length consists of 2 bytes, therefore Packet length for this command will be:
00 0f
7. Go to https://www.lammertbies.nl/comm/info/crc-calculation to calculate CRC16
Note: If client will ask for CRC16 calculation algorithm, inform them that it is described in protocol, chapter "3.1.5 CRC16".
8. Set Input type to HEX, enter Command ID + Payload as show on screenshot bellow and click Calculate CRC:
9. Write down value of CRC-CCITT (Kermit), in our case it is 6D E7
10. Convert CRC-CCITT (Kermit) from Little endian to Big endian.
Little endian: 6D E7
Big endian: E7 6D
11. Our GPRS command is ready.
Packet length: 000f
Command ID: 6C
Payload: 73756d6d65722067736d696e666f
CRC16: E76D
Expected outcome: 000f6C73756d6d65722067736d696e666fE76D