1, detect the serial line is good or bad
1) Plug the serial cable into the computer and short-circuit the 2 and 3 pins of the serial port
2) Open the serial debugging assistant
3) Click Auto-send, send a random data in the automatically sent window to see if it can receive the self-transmitted data that the serial line is normal, otherwise it is bad.
2, after the completion of the microcontroller program, take a look at the serial port for data detection
3, the meaning of the 4 lights that the module communicates with the module on the one-chip computer
1)DO lamp
Flashing indicates that the serial port of the SCM serial port and the GSM module are not communicating properly, otherwise the serial port communication is normal.
2) D1 light
The light indicates that the module is registered on the network, otherwise it is not registered on the network
3) D2 light
Lights up to start texting
4) D3 light
Lights up to end the text message
4. Connection of MCU board and GSM module
SCM ---------GSM module
VCC--------vcc (pin 3 of P5)
GND--------GND (pin 4 of P5)
RX_232 (indicating the sending of the SCM)----------RXDPC_232 (receiving of the module (pin 5 of P5))
TX_232 (represents the receipt of the SCM) ---------- TXD_PC232 (Send of the module (P5 pin 6))
Gsm module and microcontroller connection
One-chip computer connects GSM module, can connect TX and RX of asynchronous serial communication port directly, do not forget the ground wire.
Precautions:1. Different MCUs have different voltages. The input and output levels of the general GSM module are 2.85V, and the level of the 51 series is 5V. Generally, the resistance of the 2K series connected to the 51 output TX line can basically be used. If it is a 3.3V microcontroller, this resistance can be very small, a few hundred ohms can be.
2. The power supply of the GSM module and the SIM card circuit are very troublesome. First of all, most of the GSM modules use the interface of the FPC40. The distance between the cables is only 0.5mm, and it is a plastic case, which is not good for welding. If welding is not good, work is unstable. Followed by the more troublesome power supply, GSM module emission current is larger, the maximum instantaneous current 2A! Therefore, the power supply part generally uses a high-current DC-DC converter such as the LM2576 to provide a voltage of 4V. The design of the DCDC circuit itself is not easy, and it is difficult for a personal application to require a circuit board. Latency of instability. There is also a SIM card. The communication between the SIM card and the GSM module itself is a complicated high-frequency process. The circuit has strong anti-interference ability. I once tried to connect them with wires and dropped them in ten minutes. Therefore, the SIM card part needs to be carefully designed. Do not look at only five data lines.
MCU control TC35GSM module method
1, hardware connection
The circuit shown in the figure below only needs to design a TTL-to-RS232 level circuit, which is connected to the UART port of the MCU, and the other end is directly connected to the TC35.
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