SNAPS Reference Manual
Contents
1. Processing Capabilities See STM32F405xx STM32F407xx full datasheet for STM32F405ZGT6 specifications Power Consumption idle __ W Power Consumption W processing video Video Processing Speed seconds video second execution time D1 1 3 v1 1 Files SNAPS Reference Manual Electrical p 5 7 Last modified 2013 6 7 D2 D2 1 D2 1 1 D2 1 2 D2 1 3 D3 D3 1 D3 1 1 STANFORD ENGINEERING C amp DH v1 1 Bill of Materials C amp DH v1 1 CAD Altium C amp DH v1 1 Gerber Files Sierra Proto Express No Touch is recommended AstroDev Lithium Radio Switch PCB Evolution Switch v0 1 v0 1 About The SNAPS Switch PCB is a board designed for attaching flight control switches to the body of the spacecraft It breaks out three MDS6500AL02PS switches to a Hirose DF13 5 connector A wiring harness splits the connections between the Battery Supervisor PCB 3 wires and the C amp DH board 2 wires Two switches are used to detect SNAPS exit from the CSD while the other is used to prevent the Lithium Radio from turning on before exiting the parent spacecraft These switches do not need to handle significant amounts of current as they are used to control the gates of MOSFETs on the C amp DH and Battery Supervisor PCB v0 1 of the Switch PCB was designed in conjunction with and is compatible with the C amp DH v1 1 and the Battery Supervisor v0 2 PCB s The PCB design rules are set fo2. DH board are explicit switches requiring current to flow through the switch to activate a function D1 1 2 v0 1 Specifications Dimensions _ xX XxX Weight 8 Processing Capabilities See STM32F405xx STM32F407xx full datasheet for STM32F405ZGT6 specifications Power Consumption idle __ W Power Consumption W processing video Video Processing Speed _ seconds video second execution time D1 1 3 v0 1 Files e C amp DH v0 1 Bill of Materials e C amp DH v0 1 CAD Altium e C amp DH v0 1 Gerber Files Advanced Circuits 33 ea is recommended e SD card correction PCB D1 2 C amp DH v1 1 D1 2 1 v1 1 About SNAPS C amp DH v1 1 fixes the schematic and footprint layers present in v0 1 while also designing within the constraints of the mechanical structure C amp DH v1 1 not only is compatible with STRUCT v but addresses the interconnectivity of PCB s through SNAPS Reference Manual Electrical p 4 7 Last modified 2013 6 7 STANFORD ENGINEERING wiring harnesses and a Samtec FSI 110 03 G D AD connector to interface with the Battery Supervisor PCB Below follows a discussion of the upgrades from v0 1 to v1 1 and new features in each sub circuit e Overall Power Topology The overall power architecture becomes more streamlined between v0 1 and v1 1 USB power and external DC power are combined into a USB 3 0 connector sitting on the battery supervisor that can provide 900 mA nominally or 15
3. 00 mA while charging a battery Through the board to board connector only two power nets are received VBATT 2 7 4 2V nominal and VBUS 5 0V nominal VBATT and VBUS are combined with an ideal diode controller in order to provide power to the radio camera 3 3V logic etc e Radio Protection the radio is prevented from receiving power until SNAPS has exited the CSD by manipulating the SHDN pin of the protection IC e Solar MPPT the solar PCB does not provide power directly to the C amp DH board rather the battery supervisor lets the MPPT see a battery and subsequently distributes the battery voltage to the C amp DH PCB through a Samtec TMM 102 06 S D SM connector e Safety Interlocks we chose DF13 connectors to interface with a switch PCB controlling on board P FETs in the power path because finding connectors that were small and could handle the required current became difficult e Inter PCB Connector the Samtec FSI series board to board connector was chosen because of the desired spacing between boards 3mm The connector is soldered to one board and the other has pads to receive spring pins e Wiring Harness Connectors the Hirose DF13 series of connectors is used because of its low profile and acceptance as a space worthy connector As of v1 1 separation switches control gates of MOSFETs so negligible current is required to operate the interlocks D1 2 2 v1 1 Specifications Dimensions oX Kk Weight g
4. STANFORD ENGINEERING D Reference Manual Electrical The SNAPS Reference Manual is a what is guide enumerating the specifications of SNAPS PCBs For each revision of each item related files are listed Please ensure that you are viewing files for the correct version Oldest revisions come first so readers can easily follow the design decisions and changes made to each revision of an item For convenience here is a link to the root of the SNAPS Files Distribution DIL C amp DH PCB EVOlUt N eG icc cicc ssissecsicosnccntes siasedvecscsueossansedsucsesaloadbouodes saccesdasbadalsssvactdeaiecasiaesssnnsdestdentslepseevie 3 DTA CADH VO Loerie oeenn ea an a E matin tenia ete ates eee eto eoe 3 DEEV R ADO a ea E AEE E ie 3 D1 1 2y0 1 Specificati is recie E N E E E deca 4 DI 13 VOLE File S 2 oeseis anes saeco bass sheath eee a ae a es 4 MU aT Vi Mes eos swsccsics bg na datvrs a a a a aoa dea tac encase a E 4 D121 yI ABOU wccsessssistusccatesednaeiiasuncai vee cvanasbas nccdiiet dai ra rE des peed dad ndadsbas sane earder ENA Undeds nies 4 D122 yl l Sp cificati nS sissie senssa e esa aE a E a A a E EEEa REA Eaa 5 JDA EAAS a A A ED r l l S EEE E EEEE EE 5 D2 Switch PCB Eyo l toi asnan eae ee eee 6 D2 WeSC VO e 3 ccassaizaceacces E E E ties Stet anceeecaeeas eeseaseteatee 6 D221 1 VOM ABOU css vcsiseasccatetesveassdsveees see deonssiav necdvtetbeuu sie veaea are Ee R wena vad sbaes Erea bbs rO VA iS 6 D2 1 2 V0 1 Specificati
5. aints ease of debugging and fast bring up System design schematic capture layout fabrication assembly and some debugging were accomplished over the course of a 10 week quarter MPPT circuitry is included on this PCB however multiple footprint and schematic errors are present While the majority of the functionality most useful is the SD card dual port interface it is not recommended that this PCB be used as an analog for a flight ready SNAPS implementation Below follows a discussion of the design decisions made in each sub circuit of v0 1 e Processor the STM32F40x processor was chosen because of the familiarity of the board designers with this processor the attractive performance and peripheral specifications and the built in parallel memory interface that would enable large image processing programs to run e Overall Power Topology we chose to use two 18650 cells that have space heritage in parallel to avoid the need to balance batteries Some circuitry requires less than battery voltage i e 3 3V for the microcontroller and some requires more than battery voltage i e 5 9V for the Lithium Radio and 5V for the HackHD Also the system must run off of a 5V input from an external power source This external power source is ORed with the battery to provide a local power bus The LTC4415 was chosen for its efficiency in ORing power supplies and its current limit abilities To accommodate the range of devices th
6. e digital logic is powered by linear regulator from the ORed bus The LDO that we chose lowered the output voltage if the input fell too low due to the battery s falling state of charge To provide power to the radio and camera we implemented a high efficiency boost converter to 8 5V using the LT3959 Because the camera is not expected to run for a significant amount of time we chose to use a linear regulator from 8 5V to 5V to provide camera power e Radio Protection extra precautions were taken to protect it against a malfunction of the LT3959 boost converter While a Zener diode and fuse were considered the LTC4363 was used to provide OV UV OC protection for the radio The IC will retry powering the device after a fault has occurred The extra complexity of this circuit was deemed necessary for protecting the most expensive component of the satellite e Solar MPPT the SPV1040 maximum power point tracking battery charger was chosen as the interface between the solar array and the battery bus in order to collect the most energy possible from SNAPS relatively small solar array Concerns about the SPV1040 s ability to track the MPP of a triple junction solar cell due to a SNAPS Reference Manual Electrical p 3 7 Last modified 2013 6 7 ay J STANFORD S9DL y ENGINEERING SDRE ia an perturb and observe strategy arose More testing is required to determine the interaction of triple junction cells with terrestrial
7. ons oii icebee te ctuieecossslesimeeluncocesles a6 cdebusaca she bet EE hen EEES EEA EEES EEEE 6 D2 1 3 V0 1 Bill Of Mater alS cccssiissccsiccssessesaesesincsscostessasessvesacsgtesnsiessseaareatives svebeestaceatnensseavessacestimensanee 6 D3 Solar PCB Evolution sissies cccvede dias seis ches veces suds sly otevvedes ana veds r does yedesius cds oteenedes ido rN E r r a 6 TDS ASO lar VOM E E E E E E E T 6 D3 Ll VOI ADOUAT E Na 6 D3 1 2 V0 1 Specificati ns asic teue whee teont ie ese ls serea thee besa sdes Se cntbeus Beers te onthe tous ee EEE Ea eiis eee eel 7 D3 1 3 v0 1 Bill of Materials cccccccccssccccccccccccesssseececcceeccasessseeeccceeeesauaeseeeeecceseesaaaaeseseceseseeeuaaeness 7 D4 Other EMS sornes vabv odes vedws dus ody r neds ndea sade odeavalosiuysdly ndecbele pias vedanta beuvelaysedecaoesestaesales 7 SNAPS Reference Manual Electrical p 1 7 Last modified 2013 6 7 STANFORD ENGINEERING Changelog Rev Date Author Comments A 20130517 MCP Initial Revision B 20130520 MCP Updated style of project links C 20130607 MCP Project files link updates and TOC SNAPS Reference Manual Electrical p 2 7 Last modified 2013 6 7 STANFORD ENGINEERING D1 C amp DH PCB Evolution D1 1 C amp DH v0 1 D1 1 1 v0 1 About The C amp DH v0 1 Flat Sat PCB is the first implementation of the initial SNAPS architecture The board was designed with the following in mind no space constr
8. r low cost manufacturing v0 1 Specifications Dimensions X_ Xx Weight g v0 1 Bill of Materials e Switch v0 1 Bill of Materials e Switch v0 1 CAD Altium e Switch v0 1 Gerber Files 2 50 ea at BatchPCB Solar PCB Evolution Solar v0 1 v0 1 About The SNAPS Solar PCB performs multiple functions e Fastening two Spectrolab UTJ solar cells onto the structure e Boosting solar cell voltage to battery voltage with the SPV1040 MPPT IC e Attachment of the Bodipole antenna along with tuning circuit Two Solar PCBs cover the large faces of either side of SNAPS in order to both maximize solar array space and cover SNAPS internal elements Power is transferred from the MPPT circuit to the Battery Supervisor PCB using Samtec TMM 102 06 S D SM connectors which tolerate large amounts of vertical misalignment The Solar PCB is designed to be SNAPS Reference Manual Electrical p 6 7 Last modified 2013 6 7 STANFORD ENGINEERING symmetrical allowing for one design to cover both sides of the spacecraft The onboard SPV1040 maximum power point tracking MPPT IC uses a boost topology to convert the lower solar cell input voltage to the higher Li Ion battery voltage Significantly higher solar array efficiency may be achieved using an MPPT D3 1 2 v0 1 Specifications Dimensions Xx Weight g Input Voltage Range V Input Current Max _A Maximum Power W Maximum Output Voltage _ V D3 1 3 v0 1 Bill of Material
9. s e Solar v0 1 Bill of Materials e Solar v0 1 CAD Altium e Solar v0 1 Gerber Files Sierra Proto Express No Touch is recommended e Spectrolab UTJ Cells D4 Other Items e SNAPS Battery Supervisor PCB Pumpkin o Full documentation on the Pumpkin built SNAPS Battery Supervisor PCB can be found link e HackHD o The HackHD can be purchased from Sparkfun Electronics The user manual is available on this page e AstroDev Lithium Radio o AstroDev provides documentation on its Lithium Radio here SNAPS Reference Manual Electrical p 7 7 Last modified 2013 6 7
10. sunlight and the SPV 1040 e Memory Architecture in addition to the memory space natively available to the STM32F40x processors the MCU may access the SD card using a SPI interface The MCU may also access a 2Mb FRAM storage IC over SPI to store non volatile memory The MCU also may use its built in FSMC interface to communicate with the 4MB onboard SRAM Using macros explained in the source code a variable may be placed in the memory space residing externally when it is declared e Dual Port SD Interface because the HackHD only exposes control signals via a 9 pin header we chose to host its SD storage on the C amp DH board using an interface board and wiring harness to simulate the microSD card of the HackHD In order to take files off of the SD card the MCU must be able to ensure that the HackHD is not in possession of the SD card The ADG711BRZ switch was selected for switching the HackHD s access to the onboard SD card By enabling the switch signals from the HackHD s microSD adapter board may pass through to the card In order to prevent the HackHD from driving against the MCU s pins during communication care must be taken to place the MCU SPI pins in a high impedance mode e RS 232 Interface in order to test with a less expensive radio module hardware was included for communicating over RS 232 with an AstroDev Helium radio that SSDL already owned e Safety Interlocks the safety switches on v0 1 of the SNAPS C amp
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