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How many layers of abstraction and indirection are between your Python code and machine instructions?

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What if that number could be one and Python itself was the operating system?

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That would be so amazing, right?

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In fact, it is amazing, and it's called MicroPython.

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This is show number 17.

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It's MicroPython with guest Damian George.

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You're listening to Talk Python To Me, and this was recorded on Thursday, June 25, 2015.

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I'm a developer in many senses of the word, because I make these applications, but I also use these verbs to make this music.

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I construct it line by line, just like when I'm coding another software design.

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In both cases, it's about design patterns.

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Anyone can get the job done.

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It's the execution that matters.

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I have many interests.

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Sometimes it can flit.

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My creativity can usually be...

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Welcome to Talk Python To Me, a weekly podcast on Python, the language, the libraries, the ecosystem, and the personalities.

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This is your host, Michael Kennedy.

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Follow me on Twitter, where I'm @mkennedy.

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Keep up with the show and listen to past episodes at talkpythontome.com.

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And follow the show on Twitter, where we're at Talk Python.

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This show will be talking to Damian George about rethinking the Python runtime for embedded microcontrollers and his implementation, MicroPython.

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This episode is brought to you by CodeShip and Hired.

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Thank them for supporting the show on Twitter via at CodeShip and at Hired underscore HQ.

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Before we get to the interview with Damian, I'd like to give a shout out to Ganesh Kupan.

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Ganesh suggested this topic for the show, and I think it's a great one.

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Ganesh, thank you for sending that in and making this happen.

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Now, let me introduce Damian.

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Damian George is a theoretical physicist at the University of Cambridge and the creator of MicroPython.

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Damian, welcome to the show.

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Hi, Michael.

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Thanks.

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Yeah, this is really great.

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We've talked a lot about software, and we've even talked a little bit about robots on the show before.

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And now we're going to talk about sort of the most low-level stuff you can do with Python that I know of.

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We're going to talk about running Python directly on microchips and microcontrollers, right?

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Yes, that's right.

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Yeah.

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Your project, MicroPython, at micropython.org is really cool.

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Thank you.

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Yeah, you're welcome.

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And some of the listeners said, hey, you really need to have Damian on your show and talk about this stuff because what you guys are doing, it's really amazing.

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And so we're definitely going to do that.

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We're going to talk all about that.

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But before we do, maybe you could tell me a bit about your background, how you got into programming, how you got into Python, that kind of thing.

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Okay.

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Well, I mean, I've always liked computers and using computers and programming since I can remember.

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I know that I've written many languages, toy languages, ever since I could start programming.

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It's always been sort of a passion.

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I think anyone who gets into programming at some stage tries writing their own language.

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That's why there's so many of them.

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But it's a really great way to understand how a computer works is by inventing your own language or at least implementing something that already exists.

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That's sort of something that I did in my spare time.

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But actually, formally, I also did a computer engineering degree at university, which was based around microcontrollers and designing computers and designing instruction sets and writing operating systems and those kinds of low-level things.

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So that was really good to get an actual formal training so that you're forced to be exposed to all the things that maybe you didn't want to study.

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Absolutely.

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Was that mostly in C or C++?

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And what languages and stuff did you use in that field?

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We learned a lot of languages like Haskell and Java and C and C++.

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So, yeah, but I mean, it was a bit about learning languages, but also you learn algorithms like hash tables and things like that.

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And then, you know, you learn, I mean, you learn how to write a compiler.

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And it's not so much about the language.

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It's about the concepts and the algorithms.

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Right, like the abstract syntax trees and things like this, yeah?

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Yeah, that's right.

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That's right.

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So, I mean, this is what I studied.

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I actually also studied theoretical physics and pure math.

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So, I did a lot of extra stuff.

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And all these things, I think, sort of tie in, in the end, to the same kind of way of thinking, is that you think very methodically and you try and solve problems.

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And you use computers a lot in maths and physics to solve problems because they're so difficult nowadays that you can't just do it with a pen and paper.

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Yeah, I think you're totally right.

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My background is I was working on my PhD in math as well, and I got into computers to trying to do research with math.

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And, like, you're going to have to learn to program this thing.

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And it turned out I liked computers better, so I never did get a PhD.

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But I totally know where you're coming from.

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That's awesome.

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In physics, if you're an experimental physicist, a lot of the time you end up doing just a lot of programming, like Monte Carlo simulations and data analysis and things like that.

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And, I mean, yeah, if you like the kind of stuff, it's really good.

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But if you don't, you know, maybe if you want to build an actual apparatus, then you probably need to be an engineer.

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I think, yeah, my background is all these things combined.

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And, yeah, I just really like the technical side of things.

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That's cool.

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Both programming and hardware.

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Yeah, so how did you get into Python?

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You started out in this sort of what to me feels more like, you know, the majority of the work is done in C, C++, Fortran, that kind of space with physics and operating systems and so on.

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And then somehow you ended up in Python, right?

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Yeah, I mean, I think it's good if you know more than one language or more than two or more than five languages.

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And Python is such a popular language and for a good reason.

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It's a very nice language.

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And so, yeah, it's just one of the ones that you will, I think, eventually learn if you're into programming.

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And, yeah, I mean, yeah, I just, I guess just stumbled across it like all the other languages that people learn, like C and C++.

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Because, yeah, I mean, C is a great language and I love writing code in C.

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I mean, I know it's a very old language, but it allows you to be really close to the hardware.

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I mean, a line of C translates to a few lines of assembly and you sort of know what's going on.

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And, yeah, that means you have to write more code to do the same sort of thing as you would in a higher level language.

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But it gives you more power and when you need it, speed.

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But then, of course, you want something like Python to say when you don't, you're not so worried about the efficiency and you're more worried about writing something quickly and expressing your idea in a very quick way and sort of a very clean and clear way.

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So a Python program is, you know, you think it and then you sort of put your thoughts on it in code and it's sort of the same thing.

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Yeah, that's a lovely thing about Python, isn't it?

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Yeah, yeah, exactly.

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You just, you know, you don't have to allocate lists and make links in the list.

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You know, it just works having a list or it just works having a hash table, a dictionary.

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And, you know, you have lambdas and you have list comprehension and you have generators.

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And these things allow you to think in a certain way.

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And if you're writing in C, you don't think about generators and you don't think about sort of closures because they're really hard.

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But they're really good concepts.

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And a language that allows you to express those concepts easily is a good language.

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I agree.

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And when I think of, you know, microcontrollers and embedded devices, I typically think of people using C because they want to squeeze that extra 5% of energy or performance or, you know, those are more or less the same thing in some sense.

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Right.

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You've taken the opposite perspective.

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You've made Python suitable for microcontrollers rather than saying we're going to use a language that already sort of matched to the metal.

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That's really awesome.

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So you call this project MicroPython, right?

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Yeah, that's right.

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MicroPython.

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I think the name says it all.

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That's awesome.

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If you want Python on a microcontroller, then that's what you need.

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I did it as a sort of, to begin with, it was more of a can it be done question.

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Because, you know, I just, it's technically interesting to try and put a language as big and as high level and as dynamic and as memory hungry as Python on a really small microcontroller, which has very, very, very little memory.

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So that was kind of what started it for me was just the technical interest.

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But at the same time, I also thought, you know, why not pick another language or why not just, I mean, C is already on microcontrollers and stuff, but why even choose a high level language to start with?

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And my reason is that because microcontrollers now are a little, you know, are more powerful than they were a few years ago when they had almost no memory at all, you know, like 100 bytes or something.

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Now they have 100 kilobytes.

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And that's starting to be interesting.

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They also have really sophisticated peripherals.

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So you buy, you know, a $1 chip and it has all these UART and SPI and I2C and ADCs and DACs and all these peripherals that do great things and are very, very powerful.

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It has DMA to do quick transfers and this kind of stuff.

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When you start writing it in C to control all of these peripherals, it gets really, really hard really quickly because you've got to, you've got so many configuration options.

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You've got so many things to think about, interrupts and interrupt levels and it becomes very quickly sort of, I mean, it can become a bit of a mess to get something to run quickly and easily.

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So if you just want to flash an LED and read some sensor, you don't need to sort of write really efficient code that you would need to or C would allow you to.

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So to do a simple thing, but a low level simple thing, like turn a light on, I mean, what you're doing is putting a voltage, five volts or three volts on a pin.

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It's a pretty basic operation.

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It's something that you can do in Python quite efficiently.

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And then once you, you can do, you know, turn up an LED on with a Python command, you can think about having a list or a dictionary of pins and then you can iterate over them or you can pass them along as objects.

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So you can start to really abstract the low level hardware.

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And it's still relatively efficient because, well, the way MicroPython is implemented, you still have running relatively efficiently on the microcontroller.

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You know, I've seen your API and it looks super clean.

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I saw your Kickstarter video and the one that you have on micropython.org is sort of the opener video to introduce people.

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That's really cool.

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Maybe let's take a step back and just real quickly tell people what MicroPython is and tell them about your board and how it came into existence.

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Sure.

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Well, so MicroPython is a rewrite, a complete re-implementation from scratch of Python sort of version three, as it were, 3.4, actually.

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So complete rewrite, no components whatsoever that are in common with CPython.

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And the aim in rewriting it was to make sure that every operation was done as efficiently and used as little and, if possible, no RAM at all.

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So that was sort of the guiding principle is use as little RAM as possible.

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So MicroPython, the software, is this re-implementation of Python.

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And it includes all of your favorites, lists and dictionaries and sets.

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And, I mean, it's complete Python 3.4 in terms of the language specification.

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Probably not the same standard library, though.

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Probably things like dbapi2 is not there or something like that.

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Right, yeah.

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So there's the language in terms of the syntax and the semantics, you know, classes and function definitions.

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And then there's the library.

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So import numpy or whatever.

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Import this, import that.

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Python famously comes with batteries included with all of the standard library and everything you need, you know, statistics to compute the mean of something and things like that.

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And these things, some of them are not sensible to run on a microcontroller and some of them won't fit on a microcontroller.

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And so not all, well, not that many of the standard libraries are available.

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But the ones that are useful are there, like JSON string parsing, for example, and regular expressions are there in a sort of cut down form.

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And, I mean, we're always looking to add more.

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It's just that the manpower to write all of these things in a micro way is not that easy.

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Do you have to re-implement every standard library package or module that you're using?

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Some of them we have, for example, JSON printing and parsing is rewritten because you want to make it efficient.

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But other things actually import directly.

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We can just copy over the CPython standard library and use that code directly.

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So, yeah, it depends what you want to do.

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I mean, the idea really is to provide micropython as the core language.

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And then if people need some extra feature, they can copy it from normal CPython and just see if it works and it should work.

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And, you know, if not, maybe it needs a few little tweaks here and there.

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But, yeah, we concentrate mostly on the core language and providing a very robust and hopefully efficient core language.

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So that's, but that's the software side of things.

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Then there's the hardware side of things, which is, so the Pyboard, which is this little microcontroller that runs micropython.

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And all the peripherals on this Pyboard are well supported, like the I2C bus or the UART, for example.

00:14:53.520 --> 00:15:00.760

And the aim with this was, well, to be able to sort of kickstart this whole idea.

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We went to Kickstarter.

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Yeah.

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Why don't you tell everybody a little bit about your Kickstarter?

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It was super, super successful.

00:15:07.100 --> 00:15:10.360

I saw you originally were going out for 15,000 pounds.

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Yes.

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And you raised 97,000 pounds or 153,000 US dollars.

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That's, you must have been super thrilled.

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Yeah.

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Well, it was, it was a great reception.

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We had a lot of people get on board.

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And yeah, I mean, it was, it was really good.

00:15:27.660 --> 00:15:29.520

I didn't expect it to be that big.

00:15:29.780 --> 00:15:36.260

I mean, as I said, it started out as a sort of technical interest to be like, you know, it'd be really great to be able to see if this would fit.

00:15:36.260 --> 00:15:40.260

And then, you know, getting it running, making a little board.

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So the idea with the board was that I could give something to the Kickstarter backers.

00:15:45.000 --> 00:15:53.000

If they back, you know, it's nice to actually have something physical as a backer instead of a piece of free software, which is going to be free for everyone.

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So the hardware was a way to sort of, to give an incentive to say, look, there's actually something physical it can run on and you can do cool stuff with it.

00:16:01.360 --> 00:16:02.160

That's cool.

00:16:02.160 --> 00:16:11.520

The work of creating it, was it mostly actually writing the reimplementation of Python or was it, how much of it was hardware work and how much of it was software work?

00:16:11.520 --> 00:16:15.420

I'd say it was about 50, 50 to begin with.

00:16:15.420 --> 00:16:18.560

Up until when I launched the campaign, it was about 50, 50.

00:16:19.280 --> 00:16:25.220

The software, I mean, yeah, I didn't write the entire thing before the Kickstarter campaign started.

00:16:25.220 --> 00:16:29.300

I wrote enough to be able to convince myself and others that it would actually work.

00:16:29.300 --> 00:16:33.200

Like you have a REPL and you can turn lights on and off and so on.

00:16:33.200 --> 00:16:37.600

So there were bits of the language missing at the Kickstarter stage.

00:16:37.600 --> 00:16:42.540

And probably 50% of the time was spent actually building the hardware.

00:16:42.540 --> 00:16:46.840

So I had to learn about these microcontrollers and how they work.

00:16:47.020 --> 00:16:52.720

The hardest thing is getting a tool chain up and running to cross compile stuff and download it and then, you know, debug it.

00:16:52.720 --> 00:16:55.320

And why doesn't my USB thing work and so on?

00:16:55.320 --> 00:17:04.100

There's a lot of really technical and difficult things to sort of get your head around when you first get into microcontrollers.

00:17:04.100 --> 00:17:09.220

And I mean, these days with their 32-bit ARM chips, they're very powerful things.

00:17:09.220 --> 00:17:13.400

And there's lots of little things that can go wrong.

00:17:14.140 --> 00:17:16.220

So, yeah, I liked it.

00:17:16.220 --> 00:17:18.000

It was a good balance of software and hardware.

00:17:18.000 --> 00:17:23.760

Then after the Kickstarter, when the hardware was finalized, it shifted more into software.

00:17:23.760 --> 00:17:37.360

And since then, it's been, you know, pretty much purely just software, improving the software both for the core language and also to control the Pyboard in a nice way and support all the features.

00:17:37.620 --> 00:17:39.260

Yeah, it looks really rich.

00:17:39.260 --> 00:17:45.300

Maybe you could tell everyone a little bit about the features of the board because when I learned about it, I was surprised at all the things it has.

00:17:45.300 --> 00:17:50.200

You know, an accelerometer, for example, storage, all sorts of stuff.

00:17:50.200 --> 00:17:56.320

It seems pretty much like I could take that, put it into something with a power source and use it.

00:17:57.380 --> 00:17:58.520

Yeah, well, for sure.

00:17:58.520 --> 00:18:01.720

I mean, the aim is you plug it into USB and it works straight away.

00:18:01.720 --> 00:18:07.380

I just need to power source and it's got so that the accelerometer is not built into the microcontroller.

00:18:07.380 --> 00:18:09.340

That's a separate little chip that's on there.

00:18:09.440 --> 00:18:19.340

But the idea of putting that on was so that people could, you know, have sort of some input to play with straight away instead of buttons or switches or something.

00:18:19.340 --> 00:18:23.000

An accelerometer is like a lot more fun to play with.

00:18:23.000 --> 00:18:30.440

On your video, you have a little app you wrote where there's a robot that can lean forwards, backwards, left, right.

00:18:30.440 --> 00:18:33.740

And as you tilt the board, the robot kind of leans in the way.

00:18:33.740 --> 00:18:37.000

And you're doing that with an accelerometer and Python.

00:18:37.000 --> 00:18:37.340

That's right.

00:18:37.340 --> 00:18:38.840

That was a really cool example.

00:18:38.840 --> 00:18:43.340

Yeah, well, I mean, that's only, you know, a handful of lines.

00:18:43.340 --> 00:18:45.360

It's just an infinite loop while true.

00:18:45.360 --> 00:18:50.860

And then you read the accelerometer, which is like one line in Python.

00:18:50.860 --> 00:18:54.940

And then you set the servo angle based on that accelerometer reading.

00:18:54.940 --> 00:18:58.420

So, you know, it really is just a few lines to do that stuff.

00:18:58.420 --> 00:18:59.500

Okay, cool.

00:18:59.500 --> 00:19:06.680

So maybe you could walk the listeners through what it's like from going, you know, file new project to having, what was it?

00:19:06.680 --> 00:19:09.500

A main.py that runs when you turn on the board?

00:19:09.500 --> 00:19:10.020

Yeah.

00:19:10.020 --> 00:19:12.860

What's the lifecycle look like there?

00:19:12.860 --> 00:19:16.580

So there's actually a few different ways of using it.

00:19:16.580 --> 00:19:18.460

Okay.

00:19:18.640 --> 00:19:29.300

So the simplest way is you just plug it in to USB and then it becomes a serial port, like a COM port, which you can log into.

00:19:29.300 --> 00:19:33.040

It depends if you use, you know, Linux or Windows or Mac.

00:19:33.140 --> 00:19:43.160

But you just use a terminal program and then you can connect to the serial port of the board and you have a Python prompt, a REPL right there.

00:19:43.160 --> 00:19:45.480

And that runs directly on the board.

00:19:45.480 --> 00:19:52.180

So you can type commands in straight away and they will be executed and do whatever you ask on the board.

00:19:52.520 --> 00:19:57.020

So that's a good way to sort of just play around with things, debug things, test things.

00:19:57.340 --> 00:20:07.020

The other way of programming it is to write your code, your script in a file and call it main.py.

00:20:07.020 --> 00:20:10.940

And you copy that to the little mini file system that's on the board.

00:20:11.820 --> 00:20:20.000

And then whenever it turns on, whenever it gets power, it runs that main.py script straight away and just does whatever you have in there.

00:20:20.000 --> 00:20:26.700

So you could have an infinite loop, you know, reading a sensor and outputting some LEDs or servo angle or something like that.

00:20:26.700 --> 00:20:29.960

And, of course, it's not just a single file.

00:20:29.960 --> 00:20:32.440

You've got the full import machinery of Python.

00:20:32.440 --> 00:20:39.800

So if you also copy some libraries to the little file system on the board, then you can import them as well.

00:20:39.800 --> 00:20:42.280

So you can do lots and lots of different things.

00:20:42.280 --> 00:20:42.840

That's cool.

00:20:42.840 --> 00:20:44.240

And how much storage space do I have?

00:20:44.240 --> 00:21:03.400

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00:21:38.420 --> 00:21:46.640

It has about just under 200 or 100 kilobytes file system, which is not very big.

00:21:46.640 --> 00:21:50.560

So you can put a few scripts and maybe log some data.

00:21:50.560 --> 00:21:54.100

But it does have expansion with an SD card.

00:21:54.100 --> 00:21:56.200

So you can put a little micro SD card in.

00:21:56.740 --> 00:22:01.820

For a few dollars, you can buy something that has a gigabyte of storage and then you can run scripts from there.

00:22:01.820 --> 00:22:06.240

So you can put everything there and log lots of data, do whatever you like.

00:22:06.240 --> 00:22:10.020

So it's expandable in that sense.

00:22:10.020 --> 00:22:11.040

Yeah, that's excellent.

00:22:11.040 --> 00:22:14.160

So you should be able to put a lot of code on there for 200K.

00:22:17.060 --> 00:22:17.760

Yeah, yeah.

00:22:17.760 --> 00:22:37.680

And yeah, the other, there's actually, well, the third way to use it is you can actually sort of, you can write your script on your PC and then run it remotely by using a small, actually another Python script, which sort of downloads your script onto the board and runs it straight away.

00:22:37.840 --> 00:22:41.460

So that's a quick way to sort of prototype your code.

00:22:41.460 --> 00:22:42.800

Yeah, yeah, that's cool.

00:22:42.800 --> 00:22:46.600

How do you get files on there other than this prototyping way?

00:22:46.600 --> 00:22:50.080

Can I, does it like show up as a drive when I connect it or?

00:22:50.080 --> 00:22:54.600

Yeah, it shows up as a USB drive and you just, it's just like a USB stick.

00:22:54.600 --> 00:22:57.240

That's it.

00:22:57.240 --> 00:22:58.060