Basic Questions

How can I capture log ?

1) Keep the debug port ( debug_RX / debug_Tx ) and follow the instructions.

2) If there is no reserved interface, you need to weld solder wire from the module.
How do I upgrade to the latest version ?

Option #1: If the following interfaces are kept as recommended, rather than the solder wire from the module, use the RS232 bridge to connect these UART signals to PC, and use PC tools to upgrade.

Option #2: SIMCom provides the client with the module upgrade protocol, which, after being built into the application code, can be used to update in the host.

Option #3: SIM900 supports the FOTA interface. Please refer to related documentation.
Modules continue to restart after the power is on, which can only be solved by removing the SIM card. Why ?

This could be due to a severe drop in the current. Measure this drop down range with an oscilloscope and set an appropriate upper limit for the VBAT pin.
Why is there no response after the AT command has been sent ?

1) The serial port is not selected properly.

2) The baud rate is set incorrectly.

3) It is recommended to send the AT command in the capital manner, which is the most important.

4) Check the format of the AT command, AT <0d><0a>.
SIM_VCC has no voltage value when the module report shows that SIM is not ready. In this case, is the module broken ?

This is normal. When the SIM card is not detected, SIM_VCC will be controlled to be non-output voltage. Check your hardware or installation.
How do I improve the precision from hardware, software, and antenna ?

Pay attention to the internal noise, especially noises from the MCU, memory, SD/TF card, camera, and LCM screen interface.

External antennas are recommended. Avoid noises as much as possible.

As for the type of antenna, a ceramic patch antenna is recommended.

Note the gain indicator if an active antenna is used. Normally, the gain should be around 20dB and the noise index should be less than 1.5.

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