C Avionics Hardware Design (SS)C.1 Avionics Board InterfacesC.2 Avionics Board Wiring and SchematicC.3 TT8/Avionics Board Pin AllocationsC.4 Avionics Board Capture DrawingC.5 Avionics Hardware TestingC.6 Avionics Circuit Board Part InformationEMFFORCE OPS MANUAL Space Systems Product Development-Spring 2003 C Avionics Hardware Design (SS) C.1 Avionics Board Interfaces It is essential to identify the interfaces in order to ensure a complete and functioning Avionics/electronics subsystem. The primary role of the Avionics subsystem is to integrate all hardware and software of the system; therefore, the Avionics hardware must interface with all other subsystems. Central to the Avionics subsystem is the Tattletale Model 8 computer. The Avionics team has chosen to utilize the Tattletale Model 8 computer (TT8), with Motorola CPU (Central Processing Unit) and TPU (Time Processing Unit), because it both suits project processing needs and is readily available in the Space System Laboratory. This computer interfaces directly with four other pieces of hardware: The Metrology computer, the voltage regulator, the Communications board, and a series of mosfets used for power amplification purposes. This hardware conceptual layout is depicted in Figure C.1-A. RWA Power AmpComputer(CPU/TPU) Comm./OpsPWR V Reg. RS 232MetrologySensors Metrology Preprocesso PWR (D)EM Figure C.1-A: Avionics Hardware Interfaces Each hardware interface is necessary and vital to each EMFFORCE vehicle. The necessity for these interfaces is explained as follows: • The Metrology computer is another Tattletale Model 8 computer. The Avionics subsystem must allow for the sending of Primary Vehicle Array (PVA) updates through a serial channel from the Metrology TT8 to the main Avionics TT8 computer. Massachusetts Institute of Technology 1 Dept of Aeronautics and AstronauticsEMFFORCE OPS MANUAL Space Systems Product Development-Spring 2003 • The Power team is responsible for the voltage regulator. However, the Avionics team is responsible for the interfacing between the voltage regulator and the rest of the system. The voltage regulator allows for a steady 5V power to come from the AA batteries to the Tattletale computers and the Avionics board. The Power and Operations teams shall address any other power concerns and notify the Avionics team in a timely manner such that any new concerns can be addressed properly in the system design. • The communications/operations hardware is the hardware that allows for the sending and receipt of all data being transmitted and received from the immediate vehicle system to the Avionics TT8 and vice versa. The Communications board interfaces with the Avionics TT8 through a serial RS232 cable connection. • A circuit design of mosfets, like the voltage regulator, is the responsibility of the Power team. However, the intergration of the mosfets into the vehicle system is the responsibility of the Avionics team. These mosfets shall ensure that the power derived from the D-cell main batteries supply the necessary level of current needed to drive the Reaction Wheel Assembly and the Electromagnets. Massachusetts Institute of Technology 2 Dept of Aeronautics and AstronauticsEMFFORCE OPS MANUAL Space Systems Product Development-Spring 2003 C.2 Avionics Board Wiring and Schematic The Metrology and Avionics Tattletale computers shall be attached to the Avionics board via one TSW-116-07-SS connector and one TSW-120-07-SS connector per Tattletale computer. The two Tattletales communicate via one Tx line and one Rx line. Four RS-232 jacks, (corresponding to the Serial1 and Serial2 lines for each computer) shall be placed on the board, in a manner such that code loading can easily occur. The Digital Ground (DGND), -MCLR, and –IRQ3 lines shall have male connectors such that a female connector can be used to load programs (DGND must be paired with either –MCLR and –IRQ3 to load either FLASH or ROM). The Communications board shall be connected to the main Avionics board via another RS-232 cable. This connection requires from Avionics a transmit, a receive, and a digital ground line. Three Ultrasonic (US) signals shall all be inputs to the Metrology TT8 while the three Infrared (IR) signals shall converge through an OR gate before metrology computer processing. This single IR signal shall also be sent to the Avionics TT8 for time synchronization purposes. Massachusetts Institute of Technology 3 Dept of Aeronautics and AstronauticsEMFFORCE OPS MANUAL Space Systems Product Development-Spring 2003 Figure C.2-A: Avionics Board Wiring Schematic C.3 TT8/Avionics Board Pin Allocations The Avionics team established the following input/output pin allocations so that every subsystem can transmit and receive data when necessary. The following pins have been allocated for the following functions on the Metrology and Avionics TT8 computers. The “TP” prefix refers to a TPU channel, and the “AD” pin and channel prefix refers to a pin connected to the TT8’s internal A/D converter. A pin on the Avionics board or on the Metrology board is signified, respectively, by an “A” or an “M” appended to either the “TP” or “AD” prefix. Table 0-A lists the Avionics computer TT8 pins, their functions, and whether it is for an input or an output signal from the Avionics computer while lists the same for the Metrology computer. Loading of software code shall occur via serial port. TT8-to-TT8 and TT8-to-Communications Board communication shall occur via serial lines made by the Avionics team. Two TPU pins and the ground pin are necessary for each of these serial lines. Massachusetts Institute of Technology 4 Dept of Aeronautics and AstronauticsEMFFORCE OPS MANUAL Space Systems Product Development-Spring 2003 Table C.3-A: Avionics IO Pin Allocations Channel/Pin Purpose Input or Output? TPA0 Actuation 1, Electromagnet Output TPA1 Actuation 2, Electromagnet Output TPA2 Reaction Wheel Output TPA3 TT8-to-TT8 Communication, Tx Output TPA4 TT8-to-TT8 Communication, Rx Input TPA5 IR (input from met.) TPA6 (not needed yet) Actuator Stop Output TPA7 Small Control Loop Input? TPA8 PWM Output Serial1 Used for loading of code Input