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Zhuoqun (Tom) Cheng, Richard West and Ying Ye
B u i l d i n g R e a l
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i me E mb e d d e d A p p l i c a t i
- n
s
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Q d u i n
- MC
A We b
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B u i l d i n g R e a l - T i me E mb e d d e d - - PowerPoint PPT Presentation
B u i l d i n g R e a l - T i me E mb e d d e d - - PowerPoint PPT Presentation
B u i l d i n g R e a l - T i me E mb e d d e d A p p l i c a t i o n s o n Q d u i n o MC A We b - c o n n e c t e d 3 D P r i n t e r C a s e S t u d y Zhuoqun (Tom) Cheng,
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Web-connected 3D Printer
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Web-connected 3D Printer Print
Remote Job Submission
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Local Slicing Correctness Verifjcatjon
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Microprocessor Atmel AVR, 8 bit, 20 MHz SRAM 8 KB I/O UART, SPI, I2C, PWM, GPIO
Printrbot Simple Metal
Web Server
Motor
Controller
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Extruder Motor Motor
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RAMPS shield: I/O extension board
Custom Controller
64 bit dual-core Atom E3825 1.33 GHz 2 GB memory 86 GPIOs, I2C, SPI, UART, PWM Intel MinnowBoard MAX
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Custom Controller
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RAMPS shield Companion Analog Circuits MinnowMAX
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Marlin Firmware
Main loop Read G-code
G-code
Translate to motor rotatjon
Timer1 Interrupt
Interpret Motor Data Stepper Motor Data
Timer2 Interrupt
Adjust fan & heater
Temperature
Temperature Control PID Temperature PID output
Variable Period 8ms Period
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Motor Extruder
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Is this bad? Why?
Marlin on Linux Original Marlin Linux Port Main loop + interrupts handlers Multjple threads Timer interrupts Periodic nanosleep AVR I/O instructjons Intel MRAA IoT library All computatjons in the main loop Betuer code structure lightupd daemon + custom spooler
Jituer of the extruder, when submittjng relatjvely large fjles MinnowMAX Linux Marlin lightupd
Spooler
Spooler
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The Timing Problem H L d γ T T T
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struct timespec period = {.tv_sec = 0, .tv_nsec = 100000}; while (1) { nanosleep(&period, NULL); /* sleep for 100 us */ mraa_gpio_write(GPIO6, HIGH); /* write 1 to gpio6 */ mraa_gpio_write(GPIO6, LOW); /* write 0 to gpio6 */ }
10 kHz Pulse Train Frequency Period Theoretjcal 10 kHz 100000 ns Measured 7.91 kHz 100000 ns + 26422 ns Original PrintrBoard 9.96 kHz 100000 ns + 401 ns
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Unstable
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10 kHz Pulse Train sysfs framework gpiolib framework GPIO Driver 15.7% 3.9% 40.1%
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Scheduler hrtjmer framework Kernel Crossing 2.2% 9.2% 29.3% Lack of API with low and predictable overheads
struct timespec period = {.tv_sec = 0, .tv_nsec = 100000}; while (1) { nanosleep(&period, NULL); /* sleep for 100 us */ mraa_gpio_write(GPIO6, HIGH); /* write 1 to gpio6 */ mraa_gpio_write(GPIO6, LOW); /* write 0 to gpio6 */ }
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struct timespec period = {.tv_sec = 0, .tv_nsec = 100000}; while (1) { nanosleep(&period, NULL); /* sleep for 100 us */ mraa_gpio_write(GPIO6, HIGH); /* write 1 to gpio6 */ mraa_gpio_write(GPIO6, LOW); /* write 0 to gpio6 */ }
10 kHz Pulse Train Real-tjme environment setup PREEMPT_RT patch Settjng scheduling priority Locking pages into memory Further optjmizatjon Shield a core from the scheduler: isolcpu, cset… Disable tjmer interrupt on a core: CONFIG_NO_HZ_FULL ….
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Lack of a simple and uniform programming interface
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QduinoMC Goals Design Easy to use Easy to port existjng Arduino program Take advantage of the multj-core Multjthread loops Pinning loops to cores Interrupt routjng Allow QoS specifjcatjon Loop budget and period Low I/O access overhead User-level I/O access
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Simple APIs based on Arduino
loop (loopID, budget, period, [coreID]) noInterrupts (device, coreID) noTimer (coreID) interruptsVcpu (device, budget, period, [coreID]) digitalWrite () / digitalRead ()
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Marlin on QduinoMC
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loop (1, 10, 100, 1), loop (2, 30, 100, 0), loop (3, 1, 80, 0) noTimer (1), noInterrupts (ALL, 1)
interruptsVCPU (I2C, 10ms, 100ms), interruptsVCPU (NIC, 10ms, 100ms)
Web server / Spooler -- default
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void setup ( ) { pinMode(GPIO6, OUTPUT); noInterrupts(ALL, 1); noTimer(1); } void loop (1, 100, 100, 1) { delayBusyNanoseconds(100000); digitalWrite(GPIO6, 1); digitalWrite(GPIO6, 0); }
10 kHz Pulse Train Again Frequency Period Theoretjcal 10 kHz 100000 ns Measured QduinoMC 9.569 kHz 100000 ns + 4504 ns Measured Linux 7.91 kHz 100000 ns + 26422 ns Original PrintrBoard 9.96 kHz 100000 ns + 401 ns Stable
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Test Object
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Higher quality Faster printjng 10% code size reductjon Intuitjve and clear code structure
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Conclusion & Future Work
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Designed and built a platgorm to ease the development of IoT applicatjons with critjcal tjming requirements Built a web-connected 3D printer as a case study analyzed 3D printers’ real-tjme propertjes Future work will extend web connectjvity to support local slicing and print verifjcatjon
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