1 / 39

Magnetometer Testing Board

Magnetometer Testing Board. Presented by Jianer Shi 04/25/2011. Sections. Sections. Background Board Design Code 2.1 Microcontroller 2.2 Graphic User Interface (GUI) From here on…. Section 1/4. Background. Background.

zita
Download Presentation

Magnetometer Testing Board

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Magnetometer Testing Board Presented byJianer Shi 04/25/2011

  2. Sections

  3. Sections • Background • Board Design • Code 2.1 Microcontroller 2.2 Graphic User Interface (GUI) • From here on…

  4. Section 1/4 Background

  5. Background • Toque coil is used to produce a magnetometer dipole which controls the satellites attitude. • In order for the toque coil to behave as expected, an accurate measurement of magnetic field is required. • Magnetometer is an essential part to determine the earth magnetic field

  6. Background • Previous testing done by Ryne Beeson in 2009 shows noise of 0.02 Gauss, which is unacceptable for accurate attitude determination and control. Further testing is suggested and a magnetometer testing board is built for easy testing and lower electronic noise.

  7. Section 2/4 Board Design

  8. Board Summary PCB Laying Tool: Eagle 5.11.0 Microcontroller: PIC18F2221-I Communication Port: Mini – USB B Power: Mini-USB 5V Crystal Oscillator: 11.0592Mhz UART Communication Baud Rate: 57600 Communication: Serial-USB (FT232RL)

  9. Design Criteria • Microcontroller • Support I2C • Support UART • Communication • Error tolerance • Board • Small size • Mountable • User Interface • Able to pool and save Matlab friendly data for later process

  10. Microcontroller • PIC18F2221-I • Minimum Pin Number to satisfy the requirement • Small size (SOIC Package) • Has 1 UART and 1 I2C • 5V Power Supply from USB • Errata page provided by manufacturer has no significant problem with UART and I2C • Compare to other Microcontrollers, this is the minimum one satisfies the design criteria.

  11. Power and Communication • Mini-Usb Port • Small size • Provide both 5V power and communication • FT232RL USB-Serial Chip • Provide 3.3V output - eliminate 2 voltage regulators and has 500mA cutoff current protection • Provide UART to USB link

  12. Crystal Oscillator • 11.0592Mhz • This choice will resulte in 0% error with a wide range of baud rate choice. • We choose 57600 baud rate

  13. Section 3.1/4 Microcontroller code

  14. Microcontroller Task Overview

  15. I2C • Communication between magnetometer and microcontroller • Library provided by i2c.h and pic18f2221.h from C18 Compiler

  16. I2C Write

  17. I2C Read

  18. Magnetometer I2C • Slave address (0x32) for write (0x33) for read

  19. Magnetometer I2C • Functions (0x40) Accelerometer Data of 3 axis (0x45) Magnetometer Data of 3 axis (0x50) Heading Data of 3 axis (0x55) Tilt Data of 3 axis Return value: 6 byte, 2 byte per axis (in hex: xxxx) (0x82) Reset the processor, no return value

  20. Magnetometer Spec • 500ms power up delay before extract data • 1ms delay for each read

  21. 3.3V to 5.5VI2C Logic Level Conversion • Logic Level conversion is necessary because components operate on different power Magnetometer3.3V Microcontroller5V

  22. 3.3V to 5.5VI2C Logic Level Conversion Source: <Bi-directional level shifter for I²C-bus and other systems. Philips>

  23. UART • Library • Usart.h • 2 Pins • TX for sending • RX for receiving

  24. Serial Protocol In order to send information that the computer side can decode, all information pulling from the magnetometer is sent through a protocol (in hex) (eeeeeeee) (00) (function 1 byte xx)(data 2 byte xxxx)(ffffffff)

  25. Serial Protocol (eeeeeeee) (00) (function 1 byte xx)(data 2 byte xxxx)(ffffffff) • (eeeeeeee) starting flag • (ffffffff) end of line • (00) There are still new function data to be transferred

  26. Serial Protocol (eeeeeeee) (00) (function 1 byte xx)(data 2 byte xxxx)(ffffffff) Functions (41) Accelerometer X (42) Accelerometer Y (43) Accelerometer Z (46) Magnetometer X (47) Magnetometer Y (48) Magnetometer Z (56) Tilt X (57) Tilt Y (58) Tilt Z (51) Heading X (52) Heading Y (53) Heading Z

  27. Section 3.2/4 Graphical User Interface(gui)

  28. Complete GUI

  29. GUI Programing Language • Python • Pyserial • wxtools • Qt4 • Matplotlib • Toolchain • Pyqt4

  30. Python • State Machine to decode protocol • 24 State to decode serial protocal • Error Tolerance imbedded even though the UART will in theory result in 0% communication error

  31. Qt4

  32. Data Saving Button • All raw data will be saved in a tabular format, This can be easily imported into a matlab vector. • Button to control start saving data and stop saving data • Reason to keep raw data • Decimal data will result Matlabunderrun (not enough precision)

  33. Real Time Plot • Based on the open source code developed by Eli Bendersky • 3 colors to display the 3 axis data on the same graph simultaneously

  34. Section 4/4 From here on ...

  35. From here on • The board will handed over to whoever is going to test the magnetometer • Since the GUI has been revised many times for easy testing, the tester will find the whole system easy to use and test

  36. Thanks!

More Related