Command and Data Handling

Command and Data Handling

Yousef AlyousefMichael Li

Introduction

• Command and Data Handling subsystem is responsible for computing and control of subsystem functions.

• The core of this subsystem is a single-board computer powered by the Motorola PowerPC 823e from Embedded Planet.

RPX Lite

• SDRAM: 64M

• FLASH: 16M

• NVRAM: 128K

• Real-Time Clock

• Interfaces:– USB

– RS-232 Serial

– PCMCIA

– Ethernet: 10BaseT

– SPI, I2C …

Requirements

Subsystem Requirements

COMM

•1 dedicated RS-232 serial port to TNC.•1 RS-232 serial port to radios.

Science Two USB ports for cameras.

ADCS I2C interface (minimum).

Tip-Mass802.11b link between main satellite and tip-mass.

Power Consumption

PartPower Consumption

(Watts)

Flight Computer 3

Wireless Interface 3

Miscellaneous Interfaces 1(max)

Total 7(max)

USB RESET SMC1 SMC2 I2C PCMCIA

General Purpose I/O Pins

FLIGHT COMPUTER (5V, 1A)

CPLDCPLD

(5V, 150mA)

USB

Interface

SCIENCERS232 DRIVER

(5V, 7mA)

MULTIPLEXER

(5V)

RADIO TNC

COMM

EPS ADCS

Multiple Wires

Wireless

INTERFACE BOARD

TIP-MASS

RS232 Serial

802.11b(5V, 1A)

System Block Diagram

THERMALINTERFACE

THERMAL

USB Interface

+5V

GND

D+

D-

Camera0

+5V

GND

D+

D-

Camera1

MUX

D+

D-

SelectVcc

Thermal Interface

Sensors in different parts of DINO

Temp. Sensor

Flight Computer

ADC

Sensor select for temperature reading

MUX

Digital Temp. readings

select

Temp. Sensor

+5V

10k

Temperature Sensors

Temperature-controlled Variable Resistor

Voltage proportional to temperature change

Watchdog and Reset Decoder

• These will be implemented in CPLD

Parts List

Part Cost Distributor Lead Time

RPX-Lite 823e

$995Embedded

PlanetA week

CPLD ~ $50 TBD A week

ADC ~ $5 Maxim 3 days

Resistors Few cents Floor N/A

Multiplexers ~ $20 TBD 3 days

Test Plans

• ADC testing requires accompanying software.

• All other interface board functionality can be confirmed with logic analyzer and multimeters.

Issues and Concerns