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AT_Commands_Guide_EN.md

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+# AT Commands User Guide
+
+This document provides detailed usage instructions for the main AT commands supported by the H11 device.
+
+## 1. AT+DEV_INIT_STA=GET
+
+**Function**: Query device initialization status
+
+**Command Format**:
+```
+AT+DEV_INIT_STA=GET
+```
+
+**Response Example**:
+```
+AT+DEV_INIT_STA=GET,4G,<4G_link>,<SIM_ready>,<NTRIP_flag>,<CSQ>,<data_back>,<upload_size>,<NTRIP_size>,GNSS,<status>,<reserved>,star,<SNR45>,<SNR48>,<SNR50>,<visible_stars>
+OK
+```
+
+**Parameter Explanation**:
+- `<4G_link>`: 4G network connection status (0=disconnected, 1=connected)
+- `<SIM_ready>`: SIM card ready status (0=not ready, 1=ready)
+- `<NTRIP_flag>`: NTRIP connection status (0=disconnected, 1=connected)
+- `<CSQ>`: Signal quality (0-31, higher is better)
+- `<data_back>`: Data upload status (0=idle, 1=uploading)
+- `<upload_size>`: Upload queue size (bytes)
+- `<NTRIP_size>`: NTRIP data queue size (bytes)
+- `<status>`: GNSS module status
+- `<SNR45>`, `<SNR48>`, `<SNR50>`: Number of satellites with SNR > 45/48/50 dB
+- `<visible_stars>`: Total number of visible satellites
+
+**Use Cases**:
+- Check device module initialization status after startup
+- Diagnose device connectivity and module status
+- Monitor network and GNSS module status
+
+---
+
+## 2. AT+NEMATIME=SET
+
+**Function**: Set NMEA output frequency
+
+**Command Format**:
+```
+AT+NEMATIME=SET,<frequency>
+```
+
+**Parameters**:
+- `<frequency>`: Output frequency in Hz (supported values: 1, 2, 5, 10)
+
+**Response Example**:
+```
+AT+NEMATIME=SET
+OK
+```
+
+**Error Response**:
+```
+AT+NEMATIME=SET
+ERROR
+```
+
+**Use Cases**:
+- Configure GNSS position data output rate
+- Adjust positioning data update frequency based on application requirements
+- Balance between update rate and power consumption
+
+---
+
+## 3. AT+NEMATIME=GET
+
+**Function**: Query current NMEA output frequency
+
+**Command Format**:
+```
+AT+NEMATIME=GET
+```
+
+**Response Example**:
+```
+AT+NEMATIME=GET,<frequency>
+OK
+```
+
+**Parameter Explanation**:
+- `<frequency>`: Current NMEA output frequency in Hz
+
+**Use Cases**:
+- Verify the current NMEA output frequency configuration
+- Ensure frequency configuration has taken effect
+- Troubleshoot positioning data update issues
+
+---
+
+## 4. AT+RTCMBASEPOS=GET
+
+**Function**: Query base station position and distance from RTCM data source
+
+**Command Format**:
+```
+AT+RTCMBASEPOS=GET
+```
+
+**Response Example** (when RTCM data is available):
+```
+AT+RTCMBASEPOS=GET,<latitude>,<longitude>,<altitude>,<distance>
+OK
+```
+
+**Response Example** (when RTCM data is not available):
+```
+AT+RTCMBASEPOS=GET,0.0,0.0,0.0,0.0
+OK
+```
+
+**Parameter Explanation**:
+- `<latitude>`: Base station latitude in degrees (positive=North, negative=South)
+- `<longitude>`: Base station longitude in degrees (positive=East, negative=West)
+- `<altitude>`: Base station altitude/elevation in meters
+- `<distance>`: Distance from device to base station in meters
+
+**Use Cases**:
+- Obtain current base station position information in RTK mode
+- Monitor distance to reference station
+- Assess differential positioning quality
+- Verify RTK connection status
+
+---
+
+## Command Usage Examples
+
+### Query device initialization status
+```
+→ AT+DEV_INIT_STA=GET
+← AT+DEV_INIT_STA=GET,4G,1,1,1,25,0,0,1024,GNSS,1,0,star,8,5,2,12
+← OK
+```
+
+### Set NMEA frequency to 1Hz
+```
+→ AT+NEMATIME=SET,1
+← AT+NEMATIME=SET
+← OK
+```
+
+### Query current NMEA frequency
+```
+→ AT+NEMATIME=GET
+← AT+NEMATIME=GET,1
+← OK
+```
+
+### Query base station position and distance
+```
+→ AT+RTCMBASEPOS=GET
+← AT+RTCMBASEPOS=GET,31.135370,121.287729,22.467,1234.56
+← OK
+```
+
+---
+
+## Important Notes
+
+1. **Command Format**: All AT commands start with "AT" and end with "\r\n"
+2. **Case Insensitive**: Commands are case-insensitive
+3. **Response Timeout**: Recommended timeout for each command is 5 seconds
+4. **Response Format**: Successful execution returns "OK", failure returns "ERROR"
+5. **RTCM Base Station Info**: Base station position is only available after receiving valid RTCM 1005/1006 messages
+6. **Frequency Setting**: Device may need restart for frequency changes to take effect
+7. **Line Ending**: Use CR+LF (\r\n) as line terminator
+8. **Serial Parameters**: Default baud rate is 115200 bps
+
+---
+
+## Related Information
+
+- **NMEA**: National Marine Electronics Association protocol, widely used in GPS/GNSS devices
+- **RTCM**: Radio Technical Commission for Maritime Services, data format for differential positioning
+- **RTK**: Real-Time Kinematic positioning technology
+- **CSQ**: Signal Quality indicator (0-31, where 31 is excellent)
+- **SNR**: Signal-to-Noise Ratio measured in dB