It's going to be really great as Rust spreads further and further into the embedded world. I know enough C to get by, but I'm always second guessing myself when things start to get complicated, and Rust has really made lowish-level programming a lot easier for me. The safety features in addition to exposing a C ABI make it a great language for build once, run everywhere (everywhere that LLVM supports, anyway). Exciting times.
Unfortunately, there's little chance for Rust to make inroads into the embedded market, tho I wish it were otherwise.
C++ has had many benefits over C for embedded s/w for many years and has similarly failed. Note that contrary to popular belief, C++ does not result in larger, more inefficient s/w than C (for the correct C++ subset).
The momentum behind the C ecosystem is so overwhelming that Rust simply will not get a foothold anytime soon.
That's why I quite like the approach of using existing C tooling and SDK, then linking in "user-land" Rust. I wanted to run stuff on the RTL8710, and it seemed crazy to start rewriting all the HAL from scratch.
But it only took an afternoon to bolt Rust into the C build because Rust's FFI story is really nice (imo). So I get the best of both worlds: existing C HAL and SDK with the pleasantness and safety of Rust.*
* With the assumption/hope that the HAL isn't buggy, since Rust will rely on that to not explode :)
Brilliant! Thanks for the proof of concept. I've been debating this method, but it looks like you got it setup relatively quickly. Almost as easy as transitioning to another C compiler/tool chain.
> The momentum behind the C ecosystem is so overwhelming that Rust simply will not get a foothold anytime soon.
You could also say this for C on Unix in 1990. Or x86 assembly for PCs in 1985. In 1990, the idea that, 25 years later, we would be deploying network services written in JavaScript was unthinkable.
Change takes time, and C won't die, ever—but history shows that change eventually does happen.
My company uses a C++ subset (no STL, no malloc) on all of our embedded projects, which are mostly on ARM Cortex-M4.
I'd love to learn and start using Rust in our work, but we are client-project-driven, so it will be hard to justify the investment and productivity drop. I think it would make it easier to attract top talent, though things are weird in the embedded world.
I had a co-worker a long time ago described this problem as being a bunch of lumberjacks chopping down trees, but who were never allowed to stop and sharpen their axe's (let alone procure the chainsaws and learn how to use those...).
I'm a C++ enthusiast interested in embedded programming but I have very little experience. What is the rationale for your company's avoidance of the STL, is it primarily binary size?
We use embedded C++ though it is mostly C with classes and sugar after throwing out STL and exceptions. I'm eagerly awaiting more embedded friendly Nim improvements since it can be plumbed into existing embedded C tool chains.
The ecosystem... from people to compilers to libraries to tutorials... is all C and its style of doing things. Gotta be as close to it as possible to have a chance. It's why the successful languages in enterprise, system space used C-like syntax. Still took a huge company basically dictating it.
Got talking to a dude on the phone (random call about something totally non-technical). Turned out he was an embedded systems engineer in the Nuclear industry. Uses Forth for everything. He strongly encouraged me to use it for any embedded hobby project.
Tl;dr: this works because the RTL8710 is an ARM core, which is supported by LLVM and thus Rust anyway.
Its a nice how-to for working with the chip though.
Just because something uses ARM doesn't mean it'll be easy to target, there's a hell of a lot more to getting something running on an embedded system than just what basic architecture it supports.
If you have analytics on your blog you'll probably find a bit more than a few hundred. Front page #1 stories often accumulate thousands of views an hour.
Delighted to see this tidy summary! I've been wading through four or five documentation sources over the past few days getting everything hooked up. I'm working on a project that uses SPI and would love to use Rust... I may pick your brains further.
Most people use these little things for sensor/data loggers (weather stations, power monitoring, indoor temperature, etc) or little widgets that need connectivity and can be tethered to a power outlet (small display showing the weather outside, etc)
The specs say it has 0.9 mA light sleep, and a 10 uA deep sleep. Assuming the specs are correct (I haven't test it yet... not sure anyone else has either) you could definitely run it off a battery if you aren't waking it up too often.
The real problem with the RTL8710 (and ESP8266, and any other chip that uses WiFi) is that WiFi is very energy intensive. It takes a lot of juice to blast out a 2.4Ghz signal.
I don't know what the numbers are for the RTL8710, but the ESP8266 uses 50-170mA when receiving/transmitting data, which will drain a battery very quickly. (Source: http://bbs.espressif.com/viewtopic.php?t=133)
Pretty much all WiFi transceivers are indeed power-intensive, but it is actually receiving that often takes more juice.
ESP8266 consumes ~70mA with both CPU and WiFi running but idle, and 15mA with CPU idling and WiFi powered down [1]. That's 55mA or (@3.3v) ~180mW for _idle_ (i.e. receiving) WiFi circuitry. Again - that's WiFi only, with exactly zero RF power transmitted.
Now transmit. EU restricts amount of RF power radiated by a WiFi station/AP to 100mW. In US and few other places you can go slightly higher, but then other challenges arise, so for practical purpose most WiFi chipsets top out at 100 mW (a.k.a. 20dBm). Assuming RF power amplifier has efficiency of 32% [2], transmit duty cycle of 50% (that's transmitting half of the time and receiving for another half - pretty intense traffic here), we get:
(100/32%)*50% = just 156mW consumed towards "blasting out" some RF.
Clearly, receiving WiFi takes more. And there is a good reason for that. Most modern designs implement Rx as: Low-noise amplifier with some bandpass filtering -> Zero-IF mixer -> quadrature ADC -> DSP. It's the latter that does FFT, I/Q constellation tracking, demodulation, forward error correction, etc. essentially in software. And that takes a lot of power.
Ah, neat. Thanks for the analysis! I always assumed it was the transmit that ate the power, simply because you need `x` amount of energy to broadcast the signal out. But I can absolutely see how it's the circuitry associated with getting a signal back into digital that could be costly instead
thank you. I suppose the critical factor is, how long and how often does it have to wake up, and more importantly, how many milliseconds of wifi power is needed to transmit whatever data was gathered.