Utilizing Low Cost Linux Micro Computer & Utilizing Low-Cost Linux ...

Utilizing Low‐Cost Linux Micro‐Computer & Utilizing Low Cost Linux Micro Computer & Android Phone Solutions on Cube‐Satellites Ahmed Farid1, Ahmed Samy2, Ahmed Shalaby2, Ahmed Tarek2, Mahmoud Ayyad2, Muhammad Assem2, Samy Amin2 1 B.Sc. Graduation project, Computer Engineering Department, October

University for Modern Sciences & Arts 2 B.Sc. Graduation project, Aerospace Engineering Department, Cairo University

O tli Outline • • • •

Problem Definition Proposed Approach Approach Description Linux Micro‐Computers

• • • •

Android Smartphones Interface Models Proposed Improvements Conclusion

Problem Definition Problem Definition • IImplementation of satellite computing functionalities as a l t ti f t llit ti f ti liti 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: – – – – –

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Autonomous operation. Operating a payload camera P idi Providing necessary interfaces. (i.e. I2C, SPI, A/D… etc.) i f (i I2C SPI A/D ) Real‐time system monitoring. Bidirectional communications handling. Utilizing Low‐Cost Linux Micro‐Computer & Android Phone Solutions on Cube‐Satellites

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Proposed Approach Proposed Approach Recommended Strategies: Recommended Strategies: • Budget cannot afford space‐qualified systems. 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

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Utilizing Low‐Cost Linux Micro‐Computer & Android Phone Solutions on Cube‐Satellites

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Approach Description Approach Description Linux Micro‐Computers

Android Smartphone

Picture

Specifications

‐ Low cost (25‐200$) cost (25 200$)

‐ Relatively low‐cost (300‐500$) Relatively low cost (300 500$)

‐700‐1000 MHz, 512 Mb RAM

‐Dual 1 GHz processor

‐ SD Card, USB, Ethernet, Audio SD Card USB Ethernet Audio

‐ 512‐2 Gb 512 2 Gb RAM

‐ Hardware I/O (µART, SPI, I2C, GPIO)

‐ Integrated camera, sensors, and SD card

‐ Power: 1‐2.3 W Power: 1‐2 3 W

‐ Power: Power: Device and usage dependant Device and usage dependant (Ex: Galaxy S3 is 0.45 W on normal use.) ‐ Weight: Device dependant

‐ Weight: 37‐45 gm Disadvantages

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‐ Missing hardware IO in some OBCs (Analog, PWM as in the Raspberry Pi)

‐ No built‐in hardware I/O


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Linux Micro‐Computers:

Sensor Readings Acquisition & Actuator Control R Requirements i

I l Implementation i

• Interface with sensors (I2C, SPI, A/D) • Control actuators (PWM) ( )

• An external MCU is used, acting as a compatibility layer (Ex: PIC16f877). p y y ( ) Connections are over I2C or µART channels.

Complications

• Simple voltage level shifters were i l implemented (5‐3.3 v). t d (5 3 3 )

• Some interfaces may not be available Some interfaces may not be available on on accessible OBCs (PWM, A/D) • Difference in voltage logic levels I2C

I2C Sensor

Linux Micro‐computer

I2C Sensor

MCU

Analog In

Analog Sensor

PWM

Analog Actuator

I2C configuration I2C configuration

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I2C

SDA SCL

Digital UART SPI Digital, UART, SPI, Audio… etc.

UART

Linux Micro‐computer

MCU I2C Sensor

I2C Sensor

Analog In

Analog A l Sensor

PWM

A l Analog Actuator

Other Hardware

Digital, UART, SPI, A di Audio… etc.

Transistor‐based Logic Level Shifter Logic‐Level Shifter

Other Hardware

Serial configuration Serial configuration Utilizing Low‐Cost Linux Micro‐Computer & Android Phone Solutions on Cube‐Satellites

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Operating Payload Camera R Requirements i


• Camera interface for image capturing • Image storage g g

• Usage of USB cameras. (Typically webcams)

Complications

• Since Linux is used, interface can be done using programming libraries or ready‐made packages (fswebcam).

• UART and I2C cameras in local markets are slow in storage process.

• Capture takes 2 seconds for 320x240 images.

25 20

Image Capture g p Duration

15

µART

10

Webcam

5 Linksprite µART Camera 12/12/2013

Playstation Eye Webcam

0 38.4K Baud

PIL

PyGame


Fswebcam 6/14


Communications R Requirements i


• Send/Receive Data with a ground‐station • Interpret commands from a ground‐station p g

• I2C, SPI, or UART are utilized in the presence of low‐level communications hardware.

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.

• Robot36 was used to convert images to 36‐ second sound. Modifying sampling rate helps reduce transmission time. d t i i ti • AFSK was used to convert binaries to sound at 1200 bps transmission speed. p p • DTMF was used to create downlink frame headers‐trailers, and as uplink commands

Data encoding workflow d kfl Downlink Transmission Example

Beacon 12/12/2013

Type: Binaries Type: Binaries

Binaries

Type: Image Type: Image


Images

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Computation & Operations Management R Requirements i


• Management of subroutines and modes. • Use of an attitude determination algorithm. g

• Modules are compiled as standalone, but called by a single controller program. y g p g

Complications • Prototypes yp 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.

G P S

S u b r o u t in e 1

1

S e n so rs M a in G S C o m m an d s O p e r a t io n s Seq u en ce   

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2

S u b r o u t in e 2

3

Autonomous subroutine initiation based on state. based on state Utilizing Low‐Cost Linux Micro‐Computer & Android Phone Solutions on Cube‐Satellites

S u b r o u t in e 3   

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Android Smartphones: Sensor Readings Acquisition, Actuator Control, & Image Capture R Requirements i


• Interface with sensors . • Control actuator • Image capture and storage.

• Sensors and camera come built‐in. Only Java codingg is required. q • OTG connection to external MCU (Ex: IOIO, Arduino, Attiny85) for actuators.

Complications • Phone has no low‐level hardware interface. Return Readings

Readings Listening

Register Sensor/Manager Object Sensor/Manager Object Accelerometer Gyroscope

Readings

Sensor Manager

GPS Magnetometer

Sensor interface code workflow 12/12/2013

Android app controlling DC fan and motor with MCU Utilizing Low‐Cost Linux Micro‐Computer & Android Phone Solutions on Cube‐Satellites

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Android Smartphones:

Computations & Operations Management R Requirements i


• Management of subroutines and modes.

• Virtual Linux OS is run in parallel to the native Android OS. (Initiated through CHROOT) ( g )

Complications • Prototypes and libraries not in Java/C are time consuming in code porting.

SSH (Commands)

Sensors

MCU

Audio

Camera

Robot36

AFSK

Attitude Determination

Sound Manipulator

SD Card (Storage)

Android Java Modules

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Linux Modules

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Android Smartphones:

Communications & Attitude Determination R Requirements i


• Manage communications with the ground. • Use of an attitude determination algorithm. g

• Using virtual Linux technique: Codes, libraries and software packages implemented on Linux p g p micro‐computers are easily ported to Android (With minor modifications).

Complications • Porting modules to Android is time costly.

• Robot36, AFSK, and Octave R b t36 AFSK d O t are utilized. tili d

Radio Transceiver (3) Audio

Comm Payload

SSTV

C fi Confirm Modulation

Android App

(2) SSH (1) SSH

Modulation Command

Images

System Logs

Actuators

Octave (On Linux) Binaries

(4) MCU

(1) Readings

Android App

Comm Audio

Android communications workflow 12/12/2013

Control

AFSK

SD Card

Images

Sensors


Control Parameters (3) SSH (2) SSH

Octave (On Linux)

Readings

Android ADC workflow 11/14

Interface Models Interface Models

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Conclusion Rapid Prototyping

Linux Possibilities • • •

Capacity building within small time and limited resources. Faster adoption of space systems development in developing countries. Attracting smaller generations to learn of space Attracting smaller generations to learn of space engineering.

Overcoming Technical‐non Technical non Difficulties

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Low‐cost Development


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Thank you for your time Thank you for your time. Acknowledgements g •

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 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.

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