Shulou(Shulou.com)06/02 Report--

How to use the AT command to operate the SIM card to send text messages, many novices are not very clear about this. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can get something.

Recently, he devoted himself to the software rewriting of the electricity information collection terminal of an electronics company, which is mainly responsible for writing the communication function between the terminal and the master station. This week we used the AT command to operate the SIM card to send text messages. I hope it will be helpful to children's shoes with similar needs.

Note: due to the C language source code, and I know very little about the hardware, many of the operation steps are rewritten according to the original logic (especially the initialization of the SMS module). If there are any errors, please add, delete or modify as appropriate.

1. Initialization of hardware

The hardware initialization is carried out in the existing code logic as follows: open serial port → restart SIM hardware module → send AT command to check the running status of the SIM card.

A) Open serial port

Serial port operation already has a very mature code, so I won't repeat it here.

B) restart the SIM hardware module

Definition of magic numbers used:

Static const unsigned char RESET_CTL = 0

Static const unsigned char POWER_CTL = 1

Static const unsigned char IGT_CTL = 2

Restart step

Hardware operation

TurnOffModel ()

Int fd = open ("/ dev/gprs_io", O_RDWR | O_NONBLOCK)

Ioctl (fd, 0, POWER_CTL)

Sleep (3)

:: close (fd)

StartModel ()

Int fd = open ("/ dev/gprs_io", O_RDWR | O_NONBLOCK)

Ioctl (fd, 0, IGT_CTL)

Ioctl (fd, 1, POWER_CTL)

Ioctl (fd, 1, RESET_CTL)

Usleep (500000)

Ioctl (fd, 0, RESET_CTL)

Usleep (500000)

Ioctl (fd, 1, RESET_CTL)

Sleep (2)

Ioctl (fd, 1, IGT_CTL)

Sleep (3)

Ioctl (fd, 0, IGT_CTL)

:: close (fd)

Sleep (5)

C) send the AT command to check the running status of the SIM card

Operation steps

AT command sent (C++ transfer format)

The result of the reply when the module is normal

Result meaning

Check whether the module is normal or not

"AT\ n"

AT

OK

OK indicates that the module is normal.

ERROR indicates module exception

Query the international mobile station label of mobile terminal

"AT+CIMI\ n"

AT+CIMI

460000973136668

The second line of digits is the international mobile station label of the mobile terminal.

This is used to record the operation of the system, but the result can be ignored.

Detect if SIM is registered to the network

"AT+CREG?\ n"

AT+CREG?

+ CREG: 0Pol 2

OK

All agreed that the results were correct.

+ CREG: mode,state

Mode:

0: prohibit network registration from actively providing the result code (default setting)

1: allow network registration to actively provide the result code in the format:

State:

0: not registered, and the module is not currently searching for new operators

1: registered local network

2: unregistered, terminal is searching for base station

4: registration is denied

5: registered and roaming

View signal valu

"AT+CSQ\ n"

AT+CSQ

+ CSQ: 13pr 5

OK

The first number (that is, the received signal strength) is considered available when it is greater than 6.

+ CSQ:

:

Valid value is 0-31. The higher the value, the better the signal. Below 16, the call may fail.

The signal strength of the module ranges from-75 to-125DB, and the conversion formula to the effective value is

31 × (125-| DB |) / 50

:

Channel frame error rate.

Set the format of SMS messages

"AT+CMGF=0\ n"

AT+CMGF=0

OK

0:PDU mode.

1: text mode.

2. Receive SMS messages

The steps are as follows:

Operation steps

AT command sent (C++ transfer format)

The result of the reply when the module is normal

Result meaning

Get the number of SMS messages

"AT+CPMS=\" SM\ ",\" SM\ ",\" SM\ "\ r"

+ CPMS: 4, 50, 50, 4, 50, 50, 50.

OK

Take the first two digits here:

4 indicates the number of SMS messages currently stored

50 represents the total number of SMS messages that can be stored on the SIM card.

Get SMS 1 information

"AT+CMGR=1\ r"

+ CMGR: 1 Jing Ji 38

0891683108200845F7240D91683121436587F9

0000617072917253231

474747A0E4ACF416110BD3CA783C66F72D905

Returns when an error occurs:

AT+CMGR=1

+ CMS ERROR:

Delete SMS messages

"AT+CMGD=1\ r"

OK

Return on error

AT+CMGD=1

+ CMGD ERROR:

PDU stream parsing of SMS messages:

0891683108200845F7240D91683121436587F90000617072917253231474747A0E4ACF416110BD3CA783C66F72D905

08

The number of bytes occupied by the SMS center number (including type code)

08 means that the next 8 bytes (that is, 16 hexadecimal digits) are SMS center numbers (including type codes)

ninety-one

SMS center number type

91 represents the international code

A1 means domestic code.

68 31 08 20 08 45 F7

SMS center number

The BCD code is used, and in this case the SMS center number is "8613800280547". That is, all bytes are swapped high and low. F is the filling code.

twenty-four

Basic parameters (TP-MTI/MMS/RP)

The meaning is unknown

0D

Sender phone number length (number, number of non-bytes, excluding type code)

In this case, 13 digits

ninety-one

Sender phone number type

91 represents the international code

A1 means domestic code.

68 31 21 43 65 87 F9

Sender phone number

In this example, the sender's phone number is "8613123456789" (please forgive me for modifying this stream to protect my privacy)

00

Parameters show how SMSC handles SM (such as FAX, Voice, etc.)

00 indicates a normal GSM type, point-to-point mode

00

User data (UD) coding scheme

00 is 7-bit code, 08 is UCS2 code

61 70 72 91 72 53 23

BCD coding, timestamp

This example is the 19:27:35 + 8: 00 zone on July 27th, 16.

fourteen

The actual length of the message.

This example is 20 bytes.

74 74 7A 0E 4A CF 41 61 10 BD 3C A7 83 C6 6F 72 D9 05

User data "this is a test code." The 7-bit code of.

The number of bytes of user data varies depending on the "encoding scheme".

The actual number of bytes of user data (1 byte is 2 hexadecimal digits) is calculated:

7-bit encoding: the actual length of the SMS message is * 7max 8, and add 1 if there is any remainder.

UCS2 coding: the actual length of the SMS.

Other ways (not recommended, only to ensure the robustness of the program): the data between the actual length of the text message and "/ rzone".

3. Send SMS messages

The steps are as follows

Operation steps

AT command sent (C++ transfer format)

The result of the reply when the module is normal

Result meaning

Send a text message

"AT+CMGS=33\ r"

>

Waiting for SMS PDU code to be entered

"0891683108100005F011000D91683121436587F90000AA

1474747A0E4ACF416110BD3CA783C66F72D905 "+ 0xA1

OK

Sent successfully.

Failed to return:

+ CMS ERROR::

The symbol number of 0xa1, which indicates the end of PDU stream transmission.

33 in "AT+CMGS=33\ r" indicates the number of bytes of information other than the SMS center number ("0891683108100005F0") in the PDU code sent (excluding 0xA1). In this case, the length of the stream "11000D91683121436587F90000AA1474747A0E4ACF416110BD3CA783C66F72D905" is divided by 2.

PDU stream parsing of SMS messages:

0891683108100005F011000D91683121436587F90000AA1474747A0E4ACF416110BD3CA783C66F72D905

08

The number of bytes occupied by the SMS center number (including type code)

08 means that the next 8 bytes (that is, 16 hexadecimal digits) are SMS center numbers (including type codes)

ninety-one

SMS center number type

91 represents the international code

A1 means domestic code.

68 31 08 10 00 05 F0

SMS center number

The BCD code is used, and in this case the SMS center number is "8613800100500". That is, all bytes are swapped high and low. F is the filling code.

eleven

Pdu Typ

SMS messages with 160 English characters / 70 Chinese characters, no SMS report

SMS messages with 160 English characters or less than 70 Chinese characters, with SMS report

51: long SMS messages (multiple merging), no SMS reports

71: long SMS messages (multiple merging), with SMS reports

00

Message Base value (TP-MR)

0D

Sender phone number length (number, number of non-bytes, excluding type code)

In this case, 13 digits

ninety-one

Sender phone number type

91 represents the international code

A1 means domestic code.

68 31 21 43 65 87 F9

Sender phone number

In this example, the sender's phone number is "8613123456789" (please forgive me for modifying this stream to protect my privacy)

00

Parameters show how SMSC handles SM (such as FAX, Voice, etc.)

00 indicates a normal GSM type, point-to-point mode

00

User data (UD) coding scheme

00 is 7-bit code, 08 is UCS2 code

Note: it should correspond to the actual length of SMS and user data, otherwise a 531 error will be returned.

AA

Validity of SMS messages (TP-VP)

00 means 5 minutes.

AA stands for longest

Other unknown

fourteen

The actual length of the message.

20 bytes. Corresponding to the coding scheme and user data.

74 74 7A 0E 4A CF 41 61 10 BD 3C A7 83 C6 6F 72 D9 05

User data "this is a test code." The 7-bit code of.

The number of bytes of user data varies depending on the "encoding scheme".

4. Close the module

TurnOffModel (), close the serial port.

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