Dual-axis Electronic Digital Magnetic Compass Module User s Guide

Transcription

1 Dual-axis Electronic Digital Magnetic Compass Module User s Guide Sure Electronics Inc. MB-SM15114_Ver1.0

2 Table of Contents Chapter 1. UART Communication Protocol Parameter Settings Output Format Command Bytes... 1 Chapter 2. IIC Communication Protocol IIC Communication Commands Address Modification... 2 Chapter 3. Terms Declination Hard Iron Compensation and Magnetic Field Calibration... 4 Chapter 4. Notes...6 Chapter 5. Contact Us Sure Electronics Inc. MB-SM15114_Ver1.0_Page i

3 Dual-axis Electronic Digital Magnetic Compass Module NOTES: Product Version : Ver 1.0 Document Version : Ver 1.0 MB-SM15114_Ver1.0_Page ii Sure Electronics Inc

4 Chapter 1. UART Communication Protocol 1.1 Parameter Settings Baud Rate: 9600bps Parity Bit: N Data Bit: 8 Stop Bit: Output Format Each frame contains 8 bytes: 1. Byte0: 0x0D (ASCII Enter) 2. Byte1: 0x0A (ASCII New line) 3. Byte2: 0x30-0x33 hundreds (ASCII 0-3) 4. Byte3: 0x30-0x39 tens (ASCII 0-9) 5. Byte4: 0x30-0x39 units (ASCII 0-9) 6. Byte5: 0x2E (ASCII Decimal point) 7. Byte6: 0x30-0x39 decimals (ASCII 0-9) 8. Byte7: 0x00-0xFF check sum (low 8bit only) 1.3 Command Bytes Command bytes are transmitted to modules by external control: 1. 0x31: measure angle refer to the output format for value returned 2. 0xC0: magnetic field calibration starts refer to the output format for value returned (000.0 degree) 3. 0xC1: magnetic field calibration ends refer to Hard iron compensation for value returned 4. 0xA0-0XAA-0XA5-0XC5: restore to factory configuration refer to the output format for value returned (000.0 degree) 5. 0xA0-0XAA-0XA5-0XC5-IIC_ADDR: modify IIC address refer to the output format for value returned (000.0 degree) and IIC Communication Protocol for IIC address range 6. 0x03+ high 8 bit: declination setting, north setting refer to the output format for value returned (000.0 degree) 7. 0x04+ low 8 bit: declination setting, north setting refer to the output format for value returned (000.0 degree) e.g. Transmit 0XC0 to the module. If the module returns a frame <0x0D-0x0A-0x30-0x30-0x2E-0x30-0x05>, it means calibration begins. LED will be illuminated and it. e.g. Transmit 0x03, 0x00, 0x04, 0x64 to the module. It the module returns a frame <0x0D-0x0A-0x30-0x30-0x30-0x2E-0x30-0x05>, it succeed to modify the declination as 10.0 degree Sure Electronics Inc. MB-SM15114_Ver1.0_Page 1

5 Chapter 2. IIC Communication Protocol 2.1 IIC Communication During communication, this module works as 24C04 and EEPROM memory. Communication is very easy. Refer to the following table for internal addresses of the module (equal to addresses of EEPROM): TABLE 2-1 ADDRESSES Internal Address Description 0x00 Unused 0x01 High 8 bit of angle 0x02 Low 8 bit of angle 0x03 High 8 bit of declination 0x04 Low 8 bit of declination 0x05 Unused 0x06 Unused 0x07 Calibration level Actually, the current angle is a 16 bit data composed by a high 8-bit data and a low 8-bit data. The angle ranges from 0 to 3599 (the resolution is 0.1 degree). Actually, the current declination is a 16 bit data composed by a high 8-bit data and a low 8-bit data. The declination ranges from 0 to 3599 (the resolution is 0.1 degree). 2.2 Commands The commands are written to the module via IIC bus. TABLE 2-2 COMMANDS Command Description 0x00+0x31 Angle measurement 0x00+0xC0 Calibration 0x00+0xC1 Stop calibration Restore factory 0x00+(0xA0+0XAA+0XA5+0XC5) configuration 0x00+(0xA0+0XAA+0XA5+IIC_ADDR) IIC address modification 0x03+ high 8 bit Declination modification 0x03+ low 8 bit Declination modification Declination is a 16 bit data composed by a high 8-bit data and a low 8-bit data, ranging from 0 to 3599 (the resolution 0.1 degree). To modify the declination, a high 8-bit data and a low 8-bit data are required to be written to this module. 2.3 Address Modification IIC address can be modified. The factory value is 0xe0. When power on, LED will flash to IIC addresses. The times of flashing will be counted from the first time the LED on and off. If commands are sent to the module right after the module is powered, LED won t flash. The module only receives the following 16-bit addresses: MB-SM15114_Ver1.0_Page Sure Electronics Inc.

6 Dual-axis Electronic Digital Magnetic Compass Module TABLE 2-3 ADDRESSES Address Times LED flashes 0xe0 0 0xe2 1 0xe4 2 0xe6 3 0xe8 4 0xea 5 0xec 6 0xee 7 0xf0 8 0xf2 9 0xf4 10 0xf6 11 0xf8 12 0xfa 13 0xfc 14 0xfe Sure Electronics Inc. MB-SM15114_Ver1.0_Page 3

7 Chapter 3. Terms 3.1 Declination Magnetic declination is the angle between magnetic north (the direction the north end of a compass needle points) and true north. Somewhat more formally, Bowditch defines variation as the angle between the magnetic and geographic meridians at any place, expressed in degrees and minutes east or west to indicate the direction of magnetic north from true north. Magnetic declinations are not the same in different places and are not the same at different time in the same place. Module s magnetic declination = original angle + magnetic declination set. For example, magnetic declination is zero and the module outputs 100 degree. Modify the declination to 10 degree and the module will output = 100 degree. FIGURE 3-1 MAGNETIC DECLINATION 3.2 Hard Iron Compensation and Magnetic Field Calibration When the environment where the compass is used changes, the magnetic field will change and the angle output will be interrupted. To eliminate the interruption, calibration is required. Following are three methods to calibrate the module: 1. Use a tactile switch to CAL pin and GND. Press the switch and the module will be calibrated. LED keeps illuminated. Keep the module horizontal and rotate the module in a cycle (about 1min is taken to rotate the module). Press the switch again and calibration ends. LED is off. 2. LED is illuminated and keeps on after controller transmits 0XC0 to module. The module responses to the data. Keep the module horizontal and rotate the module in a cycle (about 1min is taken to rotate the module). Transmit 0XC1 to the module and LED is off. Calibration ends. The module returns the current calibration level (0-9 level, the higher the level, the better the calibration). A frame is returned in a format as shown below: Byte0: 0x0D (ASCII Enter ) Byte1: 0x0A (ASCII a new line) Byte2: 0x30 (ASCII 0) MB-SM15114_Ver1.0_Page Sure Electronics Inc.

8 Dual-axis Electronic Digital Magnetic Compass Module Byte3: 0x30 (ASCII 0) Byte4: 0x30 (ASCII 0) Byte5: 0x2E (ASCII decimal point) Byte6: 0x30-0x39 calibration level (ASCII 0-9) Byte7: 0x00-0xFF check sum (low 8 bits only) Note: check sum: Byte7 = (Byte0 + Byte1 + + Byte6). Only low 8 bits are used. e.g. transmit 0XC1 to the module and the module will return <0x0D-0x0A-0x30-0x30-0x30-0x2E-0x39-0x0E>. 9 level calibration succeeds Sure Electronics Inc. MB-SM15114_Ver1.0_Page 5

9 Chapter 4. Notes 1. All parameters are tested at 5V. It s suggested to use power supply with small ripple. 2. During the measurement, the times LED flashes correspond to measuring frequency. LED keeps on during calibration. 3. Keep the module horizontal during measurement and calibration ensuring accuracy. During measurement, keep the module over 30 centimeters away from the magnet. 4. The module features memory function, that is, it can automatically save calibration coefficient and declination after power down. 5. Restoring factory settings means restoring factory-setting calibration coefficient and declination but not modifying the current IIC address V input and output level can be directly connected to the serial port, IO port of MCU and chips such as PL2303, CH340, FT232, etc. but can t be directly connected to serial port of PC. MB-SM15114_Ver1.0_Page Sure Electronics Inc.

10 Chapter 5. Contact Us Sure Electronics Co., Ltd. East zone, 3F, Building 6 Jingang Technology Innovation Center No.108 Ganjiabian Rd (ZIP: ) Qixia District Nanjing P.R.China Tel: Fax: Website: customerservice@sure-electronics.com Sure Electronics Inc. MB-SM15114_Ver1.0_Page 7