Android Phone Solutions on Cube Satellites

Transcription

1 Utilizing Low Cost CostLinux Micro Computer & Ahmed Farid 1, Ahmed Samy 2, Ahmed Shalaby 2, Ahmed Tarek 2, Mahmoud Ayyad 2, Muhammad Assem 2, Samy Amin 2 1 B.Sc. Graduation project, Computer Engineering Department, October University for Modern Sciences & Arts 2 B.Sc. Graduation project, Aerospace Engineering Department, Cairo University Problem Definition Proposed Approach Approach Description Linux Micro Computers Outline Android Smartphones Interface Models Proposed Improvements Conclusion

2 Problem Definition Implementation ti of satellite computing functionalities as a proof of concept, given the following circumstances: Minimal time span (1 Year + No prior space know how). Lesser funding for overall project. (Student funded) Lack of/import restrictions on certain components. The following capabilities are required for the onboard computer: Autonomous operation. Operating a payload camera Providing necessary interfaces. (i.e. I2C, SPI, A/D etc.) Real time system monitoring. Bidirectional communications handling. 2/14

3 Proposed Approach Recommended Strategies: Budget cannot afford space qualified systems. More focus on local markets and affordable options. Design Complexity = Possible issues = More troubleshooting time. Suitable approaches: Linux Micro Computers Android Smartphones 3/14

4 Approach Description Picture Linux Micro Computers Android Smartphone Specifications Low cost (25 200$) 200$) Relatively low cost ( $) MHz, 512 Mb RAM SD Card, USB, Ethernet, Audio Hardware I/O (µart, SPI, I2C, GPIO) Dual 1 GHz processor Gb RAM Integrated camera, sensors, and SD card Power: W Weight: gm Power: Device and usage dependant (Ex: Galaxy S3 is 0.45 W on normal use.) Weight: Device dependant Disadvantages Missing hardware IO in some OBCs No built in hardware I/O (Analog, PWM as in the Raspberry Pi) 4/14

5 Linux Micro Computers: Sensor Readings Acquisition & Actuator Control Requirements Implementation Interface with sensors (I2C, SPI, A/D) An external MCU is used, acting as a Control actuators (PWM) compatibility layer (Ex: PIC16f877). Connections are over I2C or µart channels. Complications Simple voltage level shifters were Some interfaces may not be available on implemented d( v). accessible OBCs (PWM, A/D) Difference in voltage logic levels I2C Sensor I2C Sensor Analog In Analog Sensor MCU I2C PWM Analog Actuator I2C configuration Linux Micro computer SDA SCL Digital, UART, SPI, Audio etc. Other Hardware I2C Sensor I2C Sensor I2C Analog In MCU UART PWM Analog Analog Sensor Actuator Serialconfiguration Linux Micro computer Digital, UART, SPI, Audio etc. Other Hardware Transistor based Logic Level Level Shifter 5/14

6 Linux Micro Computers: Operating Payload Camera Requirements Implementation Camera interface for image capturing Image storage Complications UART and I2C cameras in local markets are slow in storage process. Usage of USB cameras. (Typically webcams) Since Linux is used, interface can be done using programming libraries or ready made packages (fswebcam). Capture takes 2 seconds for 320x240 images. Linksprite µart Camera Playstation Eye Webcam 25 Image Capture 20 Duration 15 µart 10 Webcam K Baud PIL PyGame Fswebcam 6/14

7 Linux Micro Computers: Communications Requirements Implementation Send/Receive Data with a ground station Interpret commands from a ground station Complications Due to import restrictions, no low level long range VHF/UHF transceivers are sold. Only hand held radio transceivers (VHF/UHF) are available, with audio interface only. Data encoding workflow I2C, SPI, or UART are utilized in the presence of low level communications hardware. Robot36 was used to convert images to 36 second sound. Modifying sampling rate helps reduce transmission i time. AFSK was used to convert binaries to sound at 1200 bps transmission speed. DTMF was used to create downlink frame headers trailers, and as uplink commands Downlink Transmission Example Beacon Type: Binaries Binaries Type: Image Images END 7/14

8 Linux Micro Computers: Computation & Operations Management Requirements Implementation Management of subroutines and modes. Modules are compiled as standalone, but Use of an attitude determination algorithm. called by a single controller program. Complications Prototypes and libraries not in C are time consuming in code porting. Integrating several modules in a single C program is considerably complex. The controller program has two main parts: Listener and state computation. Attitude determination written in Matlab script is run using Octave. GPS Subroutine 1 Sensors GS Com m ands 1 M a in 2 Subroutine 2 3 O p e r a t io n s Sequence Autonomous subroutine initiation basedon state. Subroutine 3 8/14

9 Android Smartphones: Sensor Readings Acquisition, Actuator Control, & Image Capture Requirements Implementation Interface with sensors. Control actuator Image capture and storage. Complications Sensors and camera come built in. Only Java coding is required. OTG connection to external MCU (Ex: IOIO, Arduino, Attiny85) for actuators. Phone has no low level hardware interface. Return Readings Readings Listening Register Sensor/Manager Object Accelerometer Readings Sensor Manager Gyroscope GPS Sensor interface code workflow Magnetometer Android app controlling DC fan and motor with MCU 9/14

10 Android Smartphones: Computations & Operations Management Requirements Implementation Management of subroutines and modes. Complications Virtual Linux OS is run in parallel to the native Android OS. (Initiated through CHROOT) Prototypes and libraries not in Java/C are time consuming in code porting. SSH (Commands) Sensors MCU Robot36 AFSK Audio Camera SD Card (Storage) Attitude Determination Sound Manipulator Android Java Modules Linux Modules 10/14

11 Android Smartphones: Communications & Attitude Determination Requirements Implementation Manage communications with the ground. Using virtual Linux technique: Codes, libraries Use of an attitude determination algorithm. and software packages implemented on Linux Complications micro computers are easily ported to Android (With minor modifications). Porting modules to Android is time costly. Radio Transceiver Robot36, AFSK, and Ot Octave are utilized. Comm Payload (3) Audio SSTV Confirm Images Modulation Android App (2) SSH (1) SSH Modulation Command SD Card Octave (On Linux) System Comm Images Logs Audio Android communications workflow Binaries AFSK Sensors (1) Readings Actuators (4) MCU Control Android App Control Parameters (3) SSH (2) SSH Readings Android ADC workflow Octave (On Linux) 11/14

12 Interface Models 12/14

13 Conclusion Rapid Prototyping Linux Possibilities Overcoming Technical non non Difficulties Capacity building within small time and limited resources. Faster adoption of space systems development in developing countries. Attracting smaller generations to learn of space engineering. Low cost Development 13/14

14 Thank you for your time. Acknowledgements Our mentors: A. Sherif, A. Desoki, and M. Khalil for their highly valued assessments and supporting us with their knowledge and expertise in the field. My project colleagues for their cooperative work to reach project milestones. Our families and friends for their continued moral support. The overall project is presented during the poster session as #32. 14/14