3.2 Electrical
3. MSC Interfacing
3.2.1. Spacecraft Board Design MiniSatCom | 3.2.2. Schematic of MiniSatCom to Spacecraft
MiniSatCom includes one electrical and one RF interface. The electrical interface includes input power and multiple digital communication interfaces. The following schematics and board examples suggest ways to interface with the electrical and RF ports.
3.2.1. Spacecraft Board Design MiniSatCom
3.2.1.1. Board Design
The electrical interface is a 2 x 10 pin female header with 0.050in pitch, Harwin, Inc. M50-3151042.. The header can accept male headers from the component or back cover sides. The case provides a recessed pocket to enable a low profile interface to a system. The header is NOT placed symmetrically. See figure for dimensions.
3.2.1.1.1. Interfacing from Component Case Side
The minimum pin insertion from the component case is 4.5 mm. An area 1,68 mm deep is open to accommodate the pin housing.
For a through hole option consider parts like the Wurth Electronics, Inc. part 62202021121. This has a 1,5 mm pin-alignment piece and enough exposed electrical contact to extend through the product.
For a surface mount option consider parts like the FCI part 20021121-00020C4LF. This has a total height of 1,5 mm for the base and pin-alignment, and enough exposed electrical contact to extend through the product. Be careful the base does not contact the radio case. In this application, the base leads may need to be trimmed and insulated to ensure electrical isolation.
3.2.1.1.2. Interfacing from Back Cover Side
Many options will work for the pin insertion from the back cover side. To accommodate a flush-mount of the MiniSatCom, through hole pins should be used. The pin-alignment shroud on the pins may need to be removed after soldering the header to the user’s board to allow the MiniSatCom header to fully slide to the board, as there is no distance allotted for the flush mount.
Users can also stand the radio away from the board by 1,5 mm and use the same connectors as listed above. Mechanical standoffs should be used to support this configuration on the three mounting bolts.
3.2.1.2. Board Design with RF Path Embedded in PCB
The RF connection on the radio is a MMCX Jack. Any standard MMCX plug should be compatible. The connection can be made directly from a cable end MMCX plug or from a PCB mounted MMCX plug.
3.2.2. Schematic of MiniSatCom to Spacecraft
MiniSatCom has 3 digital communications modes
USART - Universal Synchronous/Asynchronous Serial Receiver and Transmitter
SPI - Serial Peripheral Interface
TWI - Two-Wire Interface
Hardware flow control pins are used to indicate data flow status. All modes of communication should follow hardware flow control for confident operations.
The pins used are:
DSR (Data set ready) – Update notice – Indicates to the host when data is ready to be read from the radio
DTR (Data terminal ready) – Indicates to the radio data is allowed to be sent to the host via serial port.
CTS (Clear to send) – Indicates to the host when the radio is available to receive a packet. The radio, due to internal buffering requirements, will drive CTS high after each data packet while internal buffering is performed. The radio is ready to receive data when CTS is low.
3.2.2.1. Sample USART Asynchronous Schematic with Outputs 1, 2
3.2.2.2. Sample SPI Schematic with Outputs 1, 2
This will be included in a future version of this document.
3.2.2.3. Sample USART Synchronous Schematic with Outputs 1, 2
This will be included in a future version of this document.
3.2.2.4. Sample TWI Schematic with Outputs 1, 2
This will be included in a future version of this document.