Now is the time to create your own (m)Ruby computer
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The document outlines the author's journey in creating a small computer called 'family mruby' for running Ruby scripts, detailing the technical aspects of selecting components, schematics, and software implementation. It emphasizes the advantages of using mruby for constrained devices and addresses challenges such as limited memory and hardware interrupts. The author shares their experiences and encourages others to enjoy the maker lifestyle by creating their own devices.
Now is the time to create your own (m)Ruby computer
- 2. What’s your childhood dream ?
- 3. PLAYING VIDEO GAMES FREELY
- 5. FAMILY BASIC My longing programing hardware using BASIC on Family Computer(NES)
- 7. You can make your own computer with mruby!
- 8. WHO AM I? Katsuhiko Kageyama “kishima” @ twitter/github • Embedded software engineer in a manufacturing company • Making mruby devices • Personally, producing technical books about mruby and original devices in TechBookFest, Comic Market and Maker Faire(2020 Tsukuba).
- 10. Agenda •How to create your computer •Why mruby? •Important technical things about mruby
- 11. GOAL OF MY DEVELOPMENT •Creating my small computer to run Ruby scripts like “Family BASIC” •I call it “Family mruby”
- 12. How to create your computer DEFINE REQUIREMENTS FIND COMPONENTS MAKE A SCHEMATICS MANUFACTURING THE DEVICE IMPLEMENT SOFTWARE
- 13. Define requirements Find components Make a schematics Manufacturing the device Implement software Each steps are no so difficult for software engineers According to your idea Find components which satisfy your requirements. DigiKey is a good worldwide supplier Digital signal schematics could be simple We can use KiCAD Chinese company offers 5$ / 5 boards You need to implement basic software
- 14. Write application using Ruby! •I love Ruby •No one likes to wait for compiling C and flashing img •Shorter code is nice for the small device
- 15. Why mruby? •mruby can run on some small processors with limited memory (>400KB RAM preferred) •Simple implementation of mruby VM helps to port it to your own hardware
- 16. FINDING THE CORE PROCESSOR Board MCU ROM size RAM size Arduino ATmega328p 32KB 2KB ProMicro ATmega32U4 32KB 2.5KB ESP32 dev board ESP32-WROOM-32 4MB 520KB ESP32 dev board ESP32-WROVER-B 4MB 8MB Raspberry Pi zero ARM1176JZF-S >1GB (external) 512MB (external) ＊mruby requires >400kB memory
- 18. Implement basic software •Small processor doesn’t support rich OS like Linux. •C, C++ are common language •Difficult to avoid C/C++ because low layer are provided by C/C++ usually
- 19. My idea : System diagram Dev host ESP-IDF my device ESP32Arduino core FabGL mrbgem fro esp32 mruby compiler/VM mruby user App System App (C++) family_mruby Micro SD xtensa tool chain Serial communication PS/2 key board ESP32-WROVER-B Updating software Active speaker VGA monitor
- 20. My hardware •Small manufacturing was done by Chinese company •Case was made by my 3D-printer
- 21. DIFFICULTY OF IMPLEMENTATION •Limited memory •Always need to take care of remaining memory • Avoid creating so many Ruby objects •Low performance •Use HW function(Interruption, DMA etc.) as much as possible
- 22. INTERRUPTION • Hardware interruption is good for receiving HW event CPU Button Electrical signal Function A (running) Function B (Interruption handler) Interruption signal will change the program counter to an interruption hander
- 23. MRUBY CANNOT HANDLE HW INTERRUPTION • Cannot not touch mruby VM’s resource from the interruption handler • The handler has higher priority • Common solution is a polling method loop do if Input::available if Input::keydown?(Key::K_UP) my=-2 end if Input::keydown?(Key::K_DOWN) my=2 end end sp.move(mx*1,my*1) end Checking inputs in a loop • This is not the best in the limited CPU performance condition
- 24. SOFTWARE-LAYER INTERRUPTION • Compromised solution for handling interruption • Similar idea is applied in eLua and MicroPython https://github.com/kishima/mruby-interrupt CPU Button Electrical signal Function A (running) Function B (Interruption handler) mruby VM mruby VM do polling events Storing int. event in the handler Example:
- 25. Implementation (experimental) * vm.c * #ifndef MRB_SW_INTERRUPT #define CASE(insn,ops) L_ ## insn: pc0=p c++; FETCH_ ## ops (); L_ ## insn ## _BO DY: #else #define CASE(insn,ops) L_ ## insn: pc0=p c++; exec_interrupt(mrb); FETCH_ ## ops (); L_ ## insn ## _BODY: #endif * vm.c * #ifdef MRB_SW_INTERRUPT static void exec_interrupt(mrb_state *mrb){ if(!mrb->interrupt_func) return; while( !(mrb->interrupt_flag & 0x8000) && mrb- >interrupt_flag & 0x7FFF){ for(int i=0;i<16;i++){ int bit = (mrb- >interrupt_flag >> i) & 0x0001; if(bit){ mrb->user_mutex_func(mrb,1); uint16_t backup = mrb->interrupt_flag; mrb- >interrupt_flag |= 0x8000; //Interrupt flag mrb->interrupt_func(mrb,i); mrb->interrupt_flag = backup; mrb->interrupt_flag &= ~(1 << i); mrb->user_mutex_func(mrb,0); } } } } #endif exec_interrupt() will be executed when VM fetchs each mruby byte code.
- 27. SUMMARY •We can create our own device •I have created Family mruby •Software interruption is a good tool for making devices •Enjoy your maker life https://kishima.github.io/family_mruby/
- 28. THANK YOU!