【Espruino】NO.xx NOTE_extcomin-优快云博客

本文详细分析了在物联网（IoT）应用中，如何利用JavaScript及其在嵌入式硬件上的优势实现高效、灵活且节能的解决方案。通过对比不同平台的性能和功耗，阐述了JavaScript在简化开发流程、提高开发效率方面的显著作用。同时，文章深入探讨了如何利用JavaScript的实时交互特性与硬件设备进行无缝集成，以及如何在有限的资源下实现高效的数据处理与控制。此外，文章还介绍了Espruino等特定于微控制器的JavaScript环境，展示了其在低功耗和快速原型制作方面的独特价值。

uC issues

Toolchains

Designed for industry

Often non-free/crippleware

Badly documented

Bad multiplatform support

vendor-dependent HAL

Debugging often hard or impossible without extra hardware

Silicon Erratas

Arduino

Arduino makes things better

But who hasn't used Serial.write(...) and Serial.read() for debugging?

Bad Multitasking

Not really low power

Scripting

If running in uC then no toolchain to install

Easy to inspect and change while running

Rapid development

Source code is on the device itself

Quick to tweak

Friendly - no segfaults

Instant - more fun!

Why JavaScript?

A little bit like C,simple syntax

Loads of people know it already

Huge amount of learning material

With browers and node.js,you can run JS end to end

JSON built-in

Event-based model

Events on Hardware

Matches real world interaction

A lot like interrupts - without any pain

Low overhead cooperative multi-tasking

Easy to combine different functionality

Plays well with REPLs

Power Saving - interpreter knows when it can go to sleep,and how deeply

Power Saving

Many projects benefit from battery power or even energy harvesting

Navie LED flash on a 700mAh Li-lon battery:

Raspberry Pi : 1-2 hours

Arduino : 1-2 days

Espruino : ~6months

It's not easy. To wake up once a minute:

Start Low Speed Oscillator + Wait

Set up RTC

Set up Alarm

Set up interrupts

Turn off peripherals

Enter sleep mode

Re-initialise peripherals

In Espruino:

setInterval(function(){ ... },60000)

Why not use a desktop JavaScript engine?

Speed RAM NV Storage Power Draw

Typical Desktop 2500MHz*4 4000000kBytes 1000000MBytes ~50W

Typical ARM Mic 72MHz*1 8kBytes 0.125MBytes ~0.001W

~1000000 times less RAM

~10000000 times less storage

So add more RAM...

More parts:more expensive, bigger, 10-100x more power draw

Tessel(32Mb RAM, no OS)

Raspberry Pi(512Mb + node.js)

BeagleBone(256Mb + node.js)

OpenWRT(~32Mb)

And many others...

On-chip RAM

On PC - read all RAM in ~1sec

On uC - read all RAM in ~0.001sec

Less of everything, but 1000x more CPU power per byte.

Espruino Software

Purpose Built JaveScript interpreter for uCs

Open Source, C

No operating System

Can run in less than 8KB RAM

Program using Terminal app

Multi-line editing, command history in chip

Serial or USB CDC

Not just JavaScript

Built-in libraries:

Standard String/Array/etc

Maths(includeing FFT)

Waveform IO

HTTP(CC3300 and WIZnet W5500)

Graphics (w.Bitmap and Vector fonts)

Use require('...') to get drivers for new devices