All rightsAllreserved – All All rights reserved – Copyright © 2016 by SPACEBEL Copyright2016 by© SPACEBEL Copyright © 2012 by SPACEBEL SPACEBEL by Copyright 2012 © ESTEC – TEC-SW Final Presentation Day Dec 11th 2018 Scope of the project MicroPython script All rightsAllreserved – Byte code MicroPython MicroPython VM by SPACEBEL Cross-Compiler 2018 Copyright© 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 2 Scope of the project MicroPython script Configuration Make Pre-processing All rightsAllreserved – Byte code MicroPython MicroPython VM by SPACEBEL Cross-Compiler 2018 Copyright© Qualification Test Suite Eclipse IDE MicroPython SDE 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 3 Scope of the project Satellite Database MicroPython OBCP Configuration Make Pre-processing All rightsAllreserved – MicroPython MicroPython VM by SPACEBEL Cross-Compiler 2018 TM/TC Copyright© OBCP Engine OBCP Byte code Flight Software Eclipse IDE 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 4 Why a (qualified) Virtual Machine ? ● On-Board Control Procedures (OBCP) o Flexible flight procedures o Prepared on ground and dynamically uploaded All rightsAllreserved – o Extend flight SW functionality / simplify ground procedures by SPACEBEL by SPACEBEL o Tight requirements on OBCP execution environment ! 2018 Copyright© ● Payload Control Software o High-level execution environment o Must provide access to minimum of HW I/O 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 5 Why MicroPython ? ● Python is cool ● MicroPython is available All rightsAllreserved o Optimised for time/space – o Python 3.4 o Open Source by SPACEBEL o C implementation 2018 o Ported on various microcontrollers Copyright© o George Robotics Ltd, http://micropython.org ● Prototype port for LEON2 o “Porting of MicroPython to LEON platforms” ESA project 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 6 MicroPython VM (qualified) features ● Python 3.4 ● Object-orientation All rightsAllreserved ● Exception handling – ● Math functions MicroPython VM by SPACEBEL ● list, dict, bytearray, … 2018 ● Built-in imports Copyright© Excluded: ● Lots of built-in functions ● External imports ● Extensibility ● Most standard modules ● … ● … 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 7 VM Time/Space optimisation Controlled memory usage: ● Dedicated buffer for Python stack ● Dedicated buffer for heap All rightsAllreserved ● Garbage collector – MicroPython VM ● Heap can be locked by SPACEBEL 2018 Copyright© 2 object representations impacting memory and heap usage: ● 32 bits (objects are 32 bits, but any float is allocated on heap) ● 64 bits NaN boxing (any object takes 64 bits) 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 8 MicroPython SDE features Object Make representation (RTEMS, Math lib, Configuration modules) (selected features) Import Expander All rightsAllreserved – Byte code MicroPython MicroPython VM by SPACEBEL Cross-Compiler 2018 OBCP binary Copyright© ISO checksum Eclipse IDE + PyDev plugin + Pylint 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 9 SDE Import Expander MicroPython MicroPython In addition: script script ● Can replace names with import their values All rightsAllreserved ● Without copying all names – MicroPython MicroPython script script by SPACEBEL Very useful for SRDB ! 2018 Copyright© import MicroPython MicroPython main script main script with Import Expander without native imports native imports 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 10 VM testing RTEMS 4.8 Edisoft/Gaisler 32 bits / 64 bits NaN boxing object representation libm/MLFS All rightsAllreserved LEON2 Emulator – (with/without instrumentation) MicroPython VM Tested on by SPACEBEL 2018 LEON2 Hardware (EUCLID FUMO) Copyright© Qualification Test Suite C Python tests MicroPython tests Spacebel tests • Automated tests • End-to-end testing • 624 MicroPython scripts 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 11 VM analyses Code coverage analysis: ● Cantata ● Removal of unused code (MicroPython VM macro configuration) ● Justification of remaining non-covered code All rightsAllreserved Continuous static code analysis: – ● Polyspace Bug Finder MicroPython VM by SPACEBEL 2018 Copyright© Call graph analysis: ● Identification of direct and indirect recursive calls ● Protection of C stack usage 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 12 VM (and related) issues Coding style: ● Remain compatible with master branch ● No applicable coding standard and no adaptation ! Floating Points: All rightsAllreserved ● NaN, -0.0 – ● Issues in libm by SPACEBEL by SPACEBEL MicroPython VM ● Issues in VM 2018 ● Issues in LEON emulators Copyright© ● Questions on IEEE FP standard RTEMS Edisoft: ● Absence of trap 0x83 (window flush) required for NLR VM SPRs: ● No raw trap handler registration (set_vector) ● 62 fixed ● 48 (minor) used as-is 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 13 VM (and related) issues 48 minor VM SPRs used « as is »: ● 27 « not implemented » issues Not implemented (examples): ● 21 « deviations » wrt C Python ● Exception raised in such case ● locals() ● array.array bytearray rightsAllreserved , semantics – MicroPython VM not complete (deletion, accessors) ● bytes, str semantics not complete (keywords) by SPACEBEL 2018 Deviations (examples): ● rsplit semantics not complete ● __init__ method not supported for all Copyright© ● float('.') --> 0.0 built-in types (Exception…) o Not allowed in CPython ● sum(['a','b','c'],'') --> 'abc‘ ● List/tuple/array/bytes/subscript slices with o Not allowed in Cpython step != 1 ● {:f}'.format(1234.) --> '1233.999999‘ o print('abcdefghi'[0:9:2]) ● 1.015625 == 1015625E-6 --> False o Precision of 1e-13 in MicroPython via str ● Deviations with multiple inheritance ● Deviations with garbage collection 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 14 OBCP Engine features ● New Flight SW component ● PUS 18 TM/TC interface All rightsAllreserved ● Additional MicroPython – module: obcp_engine MicroPython VM by SPACEBEL ● Control/monitoring of VM 2018 TM/TC Copyright© OBCP Engine ● Dynamic aspects (multi-tasking) Flight Software ● Fault containment ● Highly configurable 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 15 obcp_engine module import obcp_engine Step is observable (in HK) Possible to stop/suspend on a step obcp_engine.step(1) All rightsAllreserved obcp_id = obcp_engine.get_obcp_id() – OBCP id determined when loading by SPACEBEL by SPACEBEL obcp_engine.step(2) 2018 Returns OBET time_before = obcp_engine.get_time() as float Copyright© obcp_engine.sleep(5.0) « OS » task wait versus obcp_engine.wait_1hz_sync() synchro with HW signal time_after = obcp_engine.get_time() delay = time_after – time_before 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 16 obcp_engine module arg_buffer = bytearray(4) obcp_engine.read_obcp_arguments(arg_buffer) Arguments can be provided when OBCP is started or when it runs import sdb obcp_engine.write_db_parameter(sdb.DB_PARAM5,arg_buffer) All rightsAllreserved x = obcp_engine.read_db_parameter(sdb.DB_PARAM6) – mem_buf = bytearray(20) Data Bank access (using SRDB) by SPACEBEL by SPACEBEL obcp_engine.read_memory(sdb.MEM_EEPROM,0,mem_buf) 2018 obc_engine.write_memory(sdb.MEM_RAM,1024,mem_buf) Memory access Copyright© obcp_engine.send_tm(sdb.GROUND,128,2,mem_buf) obcp_engine.generate_event(sdb.NULL,sdb.EVT_EXAMPLE1) TM generation 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 17 obcp_engine module tc = bytearray(25) obcp_engine.format_tc(tc,sdb.HK,3,1,True,True) tc_id = obcp_engine.send_tc(tc) Separate functions to format and to send a TC acc = obcp_engine.check_tc_acceptance_acknowledge(tc_id) All rightsAllreserved compl = obcp_engine.check_tc_completion_acknowledge(tc_id) – tm = bytearray(40) TC checks (-1 returned if no ack) by SPACEBEL by SPACEBEL obcp_engine.subscribe_tm(sdb.HK,3,25,5) 2018 while obcp_engine.receive_message(tm) == 0: pass TM access through Copyright© # process tm here subscription (similar to obcp_engine.unsubscribe_tm() ground procedures) 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 18 OBCP states All rightsAllreserved – by SPACEBEL by SPACEBEL 2018 Copyright© ● High priority OBCP: 1 single VM (with queueing) ● Low priority OBCP: 10 available VM (without queue) 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 19 Dynamic aspects ● 1 VM == 1 RTEMS task ● VM tasks have lowest priority in Flight SW ● 1 VM task with « high priority » All rightsAllreserved ● 10 VM tasks with same « low priority » – o by SPACEBEL RTEMS time-slicing to share the available CPU 2018 Copyright© ● VM execution = 1 unique call ● VM control using « hook » mechanism o suspend/resume OBCP o stop/abort OBCP (with exception) o housekeeping (VM memory usage…) 11/12/2018 Qualification of MicroPython VM and OBCP Engine – Python in Space 20 Fault containment ● CPU usage cannot be limited ● Controlled access to Flight VM must run at lowest priority SW resources ● Data Bank ● Memory All rightsAllreserved – ● Python stack limited and checked ● by SPACEBEL Python heap limited and checked 2018 ● Lockable heap (no garbage collection) Copyright©