The AT command is used between the single-chip microcomputer and the GSM engine, so it is necessary to understand the format of the AT command and several common instructions. More detailed information can be referred to the GSM07.05 and GSM07.07 specification. The AT instruction sent by the single chip microcomputer is used to establish a communication link, and the command format frame of the AT instruction set is started with AT, and below is a few common AT instructions. 1. Set the short message center AT CSCA = " 8613800270500" Enter (the specific number is determined by the local operator.) 2. Receive short message cmti: "sm", x (x indicates a SIM card storage number receiving short message) AT CMGR = X Enter (from X memory reading short message) AT CMGD = X Enter (from x storage District deletion short message) 3. Send a short message AT CMGF = 1 Enter (send in text format, if used in PDU format, At cmgf = 0) AT cmgs = " 8613xxxxxxxxx" Enter "Enter a short message. CRTL z ends and sent. 4. Important Directive ATZ; E Enter Echo Off ATZ; E1 Enter Echo ON AT CREG? Enter x (x = 2 off-network, x = 1 registration, x = 0 state unknown) AT COPS? Enter to indicate whether the SIM card is accepted at cops =? Enter all available networks in the Enter. 5. Establish a voice call AT CREG? Enter (Whether Network Registration) ATD13XXXXXXXXX; Enter (voice call and data call establishment) 6. Change and save parameters AT IPR = 2400 Enter (change RS232) AT & W Enter (Save Change Parameters) 7. After entering the PIN code AT CPIN = "xxxx" communication link is created, the microcontroller can issue an information unit frame, the frame format of the information is as follows: where the frame head starting with the flag frame is a hexadecimal 10h and 02h, logo information The end is 10h and 03h, and the last two is the result of the data part according to 16-bit and subsequent samples. For the data bits, in order to avoid the end flags of the error, it is specified that each of the 10h codewords will appear, and an empty character 00h is inserted. If the information is received, the empty character should be removed accordingly. If the data portion and the BCS portion received by the receiving end are not equal to 0, it means that the transmission is an error, and the received information is lost.
