Recording: https://www.youtube.com/watch?v=DxTetwYsXvo&index=1&list=PLiVCejcvpsevQ_I9oDIK6eIgau45fWje2 The Mbed Simulator allows you to cross-compile Mbed OS 5 applications and run them on your computer.

1. Copyright © 2019 Arm
Open Hours
Mbed Simulator
Jan Jongboom
Principal Developer Evangelist
Arm

2. Jan Jongboom
Principal Developer Evangelist
jan.jongboom@arm.com

3. Developer Evangelism at Arm
Jan Jongboom
Europe
Neil Tan
APAC
Austin Blackstone
US & Japan
Daniel Lee
South Korea

4. Web development
💚

5. MCU development
😩

6. Hardware Debugger
Module (MCU+Radio)
Development
Board

7. Copyright © 2019 Arm 7
Embedded development is stuck in the 90s
Everything ASM / C / C++
Development tools only run on Windows
Paid debugger with limited number of breakpoints
Very slow feedback loop
https://www.flickr.com/photos/65290859@N05/5995262928

8. BBC micro:bit
Given to 1 mio kids in UK
True microcontroller (16K of RAM, runs Mbed)
Unique developer experience
https://pxhere.com/en/photo/1396499

9. Copyright © 2019 Arm 9
BBC micro:bit - online editor
Pseudo-language (block based)
Can output JS or C++ or anything

10. Copyright © 2019 Arm 10
I want this... But in normal C++
#include "mbed.h"
#include "compass.h"
Compass compass(I2C_SDA, I2C_SCL);
Display display;
int main() {
while (1) {
display.printf("%d", compass.read());
}
}

11. Copyright © 2019 Arm 11
Emscripten
LLVM to asm.js / WebAssembly
Runs C/C++ in the browser
Supported by Mozilla

12. Copyright © 2019 Arm 12
Mbed OS Blinky - User API
#include "mbed.h"
DigitalOut led(LED1);
int main() {
while (1) {
led = !led;
wait_ms(500);
}
}

13. Copyright © 2019 Arm 13
Mbed OS Blinky - under the covers
Cortex-M boot sequence explanation: https://www.youtube.com/watch?v=3brOzLJmeek
// Mbed C++ HAL
DigitalOut::write(int value) {
gpio_write(&gpio, value);
}
// Mbed C HAL (implemented by vendor)
void gpio_write(gpio_t *gpio, int value) {
if (value == 1) {
0x40200000 = 1U << gpio->pin;
}
else {
0x40200004 = 1U << gpio->pin;
}
}

14. Copyright © 2019 Arm 14
Places for simulation
Application
Mbed C++ HAL (generic)
Mbed C HAL (vendor specific)
Peripherals
When write to 0x40200000 comes in
call JavaScript
When DigitalOut::write is called
call JavaScript
When gpio_write() is called
call JavaScript 🎉

15. Copyright © 2019 Arm 15
Mbed Simulator in Mbed OS
Full Mbed C++ HAL
Target implements Mbed C HAL
Calls JavaScript functions from C HAL

16. Copyright © 2019 Arm 16
Challenges
Microcontroller is always busy
Interrupt handling
Single-threaded
Networking

17. Copyright © 2019 Arm 17
IP Networking
Application
HTTP Library
Mbed Networking Stack
Networking primitives
TCP Sockets, UDP Sockets
Networking hardware
DNS handling, socket management,
buffering, generic socket APIs
Node.js daemon that provides
TCPSocket and UDPSocket
(over synchronous AJAX calls)
🔐

18. Copyright © 2019 Arm 18
Runs Pelion Device Management
(DTLS, CoAP, LwM2M, X509 client certificates)

19. Copyright © 2019 Arm 19
LPWAN networking
Application
Mbed HAL
SX1276 radio driver
LoRaWAN stack
Peripherals
Device
LoRa
PHY
Packet
Forwarder
IP

20. Copyright © 2019 Arm 20
LPWAN networking
Device
Wrap in
packet forwarder
protocol
Application
Mbed HAL
Fake radio driver
LoRaWAN stack
Simulated Peripherals

21. Copyright © 2019 Arm 21
Bringing in new components
Take C++ library
Add in a few EM_ASM calls in strategic places
(#ifdef TARGET_SIMULATOR)
F.e. when flushing frame buffer over SPI for a display
Implement JS HAL and JS UI
(e.g. draw canvas and handle frame buffer updates)

22. Copyright © 2019 Arm 22
Two ways of using the simulator
Online: https://labs.mbed.com/simulator
Great for teaching
Online compiler
Share code by copy pasting the URL
Offline (requires Emscripten SDK):
$ npm install mbed-simulator -g
$ mbed-simulator .

23. Copyright © 2019 Arm 23
Simulator CLI
Install via: npm install mbed-simulator -g
Exclude or replace libraries via simconfig.json
Reads mbed_app.json
Detect where you run via:
#ifdef TARGET_SIMULATOR

24. Copyright © 2019 Arm 24
simconfig.json example
{
"compiler-args": [
"-std=c++11",
"--preload-file", "sdcard@/fs",
"--preload-file", "constants@/fs/constants"
],
"emterpretify": true,
"ignore": [
"./BSP_DISCO_F413ZH",
"./F413ZH_SD_BlockDevice",
"./utensor/sd-driver/"
],
"peripherals": [
{ "component": "ST7789H2", "args": {} }
]
}

25. Copyright © 2019 Arm 25
Debugging
Source maps can be generated by Emscripten
Debugging through normal browser JS debugger

26. Recap
Embedded development is a PITA
The web has brought so many cool tools, let's use them
Cross-compile your embedded app => ??? => PROFIT
Open source @ https://github.com/janjongboom/mbed-simulator
Live demo @ https://labs.mbed.com
https://www.pexels.com/photo/arduino-breadboard-circuit-diodes-370518/

27. Copyright © 2019 Arm
Trademark and copyright statement
The trademarks featured in this presentation are
registered and/or unregistered trademarks of Arm
(or its subsidiaries) in the EU and/or elsewhere. All
rights reserved. All other marks featured may be
trademarks of their respective owners.
Copyright © 2019
Thank You!
27