Saving PIC Microcontrollers With DIY Programmer

January 14, 2024 by Bryan Cockfield 31 Comments

When working on a project, plenty of us will reach for an Atmel microcontroller because of the widespread prevalence of the Arduino platform. A few hackers would opt for a bit more modern part like an ESP32. But these Arduino-compatible platforms are far from the only microcontrollers available. The flash-based PIC family of microcontrollers is another popular choice. Since they aren’t quite as beginner or user-friendly, setting up a programmer for them is not as straightforward. [Tahmid] needed to program some old PIC microcontrollers and found the Pi Pico to be an ideal programmer.

The reason for reaching for the Pico in the first place was that [Tahmid] had rediscovered these decade-old microcontrollers in a parts bin but couldn’t find the original programmer. Thanks to advances in technology in the last ten years, including the advent of micropython, the Pico turned out to be the ideal programmer. Micropython also enables a fairly simple drag-and-drop way of sending the .hex file to the PIC, so the only thing the software has to do is detect the PIC, erase it, and flash the .hex file. The only physical limitation is that the voltages needed for the PIC are much higher than the Pico can offer, but this problem is easily solved with a boost converter (controlled by the Pico) and a level shifter.

[Tahmid] notes that there’s plenty of room for speed and performance optimization, since this project optimized development time instead. He also notes that since the software side is relatively simple, it could be used for other microcontrollers as well. To this end, he made the code available on his GitHub page. Even if you’re more familiar with the Arduino platform, though, there’s more than one way to program a microcontroller like this project which uses the Scratch language to program an ESP32.

Close To The Metal

October 14, 2023 by Elliot Williams 81 Comments

Firmware is caught between hardware and software. What do I mean? Microcontroller designers compete on how many interesting and useful hardware peripherals they can add to the chips, and they are all different on purpose. Meanwhile, software designers want to abstract away from the intricacies and idiosyncrasies of the hardware peripherals, because code wants to be generic and portable. Software and hardware designers are Montagues and Capulets, and we’re caught in the crossfire.

I’m in the middle of a design that takes advantage of perhaps one of the most idiosyncratic microcontroller peripherals out there – the RP2040’s PIOs. Combining these with the chip’s direct memory access (DMA) controllers allows some fairly high-bandwidth processing, without bogging down the CPUs. But because I want this code to be usable and extensible by a wide audience, I’m also trying to write it in MicroPython. And configuring DMA controllers is just too idiosyncratic for MicroPython.

But there’s an escape hatch. In my case, it’s courtesy of the machine.mem32 function, which lets you read and write directly into the chip’s memory, including all of the memory-mapped configuration registers. Sure, it’s absurdly low-level, but it means that anything you read about in the chip’s datasheet, you can do right away, and from within the relative comfort of a Micropython program. Other languages have their PEEK and POKE equivalents as well, or allow inline assembler, or otherwise furnish you the tools to get closer to the metal without having to write all the rest of your code low level.

I’m honestly usually a straight-C or even Forth programmer, but this experience of using a higher-level language and simultaneously being able to dive down to the lowest levels of bit-twiddling at the same time has been a revelation. If you’re just using Micropython, open up your chip’s datasheet and see what it can offer you. Or if you’re programming at the configure-this-register level, check out the extra benefits you can get from a higher-level language. You can have your cake and eat it too!

Accurate Cycle Counting On RP2040 MicroPython

August 26, 2023 by Matthew Carlson 14 Comments

The RP2040 is a gorgeous little chip with a well-defined datasheet and a fantastic price tag. Two SDKs are even offered: one based on C and the other MicroPython. More experienced MCU wranglers will likely reach for the C variant, but Python does bring a certain speed when banging out a quick project or proof of concept. Perhaps that’s why [Jeremy Bentham] ported his RP2040-based vehicle speedometer to MicroPython.

The two things that make that difficult are that MicroPython tries to be pretty generic, which means some hackery is needed to talk to the low-level hardware, and that MicroPython doesn’t have a reputation for accurate cycle counting. In this case, the low-level hardware is the PWM peripheral. He details the underlying mechanism in more detail in the C version. On the RP2040, the PWM module can count pulse edges on an input. However, you must start and stop it accurately to calculate the amount of time captured. From there, it’s just edges divided by time. For this, the DMA system is pulled in. A DMA request can be triggered once the PWM counter rolls over. The other PWM channel acts as a timer, and when the timer expires, the DMA request turns off the counter. This works great for fast signals but is inaccurate for slow signals (below 1kHz). So, a reciprocal or time-interval system is included, where the time between edges is captured instead of counting the number of edges in a period,

What’s interesting here is how the hardware details are wrapped neatly into pico_devices.py. The uctypes module from MicroPython allows access to MMIO devices such as DMA and PWM. The code is available on GitHub. Of course, [Jeremy] is no stranger to hacking around on the RP2040, as he has previously rolled his own WiFi driver for the Pico W.

The Past, Present, And Future Of CircuitPython

August 1, 2023 by Tom Nardi 37 Comments

Modern microcontrollers like the RP2040 and ESP32 are truly a marvels of engineering. For literal pocket change you can get a chip that’s got a multi-core processor running at hundreds of megahertz, plenty of RAM, and more often than not, some form of wireless connectivity. Their capabilities have been nothing short of revolutionary for the DIY crowd — on any given day, you can see projects on these pages which simply wouldn’t have been possible back when the 8-bit Arduino was all most folks had access to.

Limor Fried

Thanks to the increased performance of these MCUs, hackers and makers now even have a choice as to which programming language they want to use. While C is still the language of choice for processor-intensive tasks, for many applications, Python is now a viable option on a wide range of hardware.

This provides a far less intimidating experience for newcomers, not just because the language is more forgiving, but because it does away with the traditional compile-flash-pray workflow. Of course, that doesn’t mean the more experienced MCU wranglers aren’t invited to the party; they might just have to broaden their horizons a bit.

To learn more about this interesting paradigm shift, we invited the fine folks at Adafruit to the Hack Chat so the community could get a chance to ask questions about CircuitPython, their in-house Python variant which today runs on more than 400 devices.

Continue reading “The Past, Present, And Future Of CircuitPython” →

Software Driving Hardware

June 3, 2023 by Elliot Williams 69 Comments

We were talking about [Christopher Barnatt]’s very insightful analysis of what the future holds for the Raspberry Pi single board computers on the Podcast. On the one hand, they’re becoming such competent computers that they are beginning to compete with lightweight desktop machines, instead of just being a hacker curiosity.

On the other hand, especially given the shortage and the increase in price that has come with the Pi’s expanding memory endowments, a lot of people who would “just throw in a Raspberry Pi” are starting to think more carefully about their options. Five years ago, this would have meant looking into what you could whip together on an Arduino-based platform, either on actual Arduino hardware or on an ESP8266 or similar, but that’s a very different beast from a programmer’s perspective. Working with microcontrollers used to be very different from working with even the smallest Linux machines.

These days, there is no shortage of microcontrollers that have enough memory – both flash and RAM – to support a higher-level environment like MicroPython. And if you think about it, MicroPython brings to the microcontrollers a lot of what people were using a Raspberry Pi for in projects anyway: a friendly interactive programming environment that was free of the compile-here, flash-there debug cycle. If you’re happy coding Python on a single-board Linux computer, you’ll be more or less happy coding in MicroPython or Circuit Python on a microcontroller.

And what this leaves us with, as hackers, is a fantastic spectrum of choices. Where before there was a hard edge between programming C on an 8-bit PIC or an AVR and working with something that had a full Linux operating system like a Pi, it’s all blurry now. And as the Pis, the Jetson, and all the other Linux SBCs are blurring the boundary with more traditional computers as they all become more competent and gain more computer-like peripherals. Nowadays your choice is much freer, and the hardware landscape more fluid. You don’t have to let software development concerns drive your hardware choices, and we think that’s a great thing.

Let Machine Learning Code An Infinite Variety Of Pong Games

February 21, 2023 by Dan Maloney 7 Comments

In a very real way, Pong started the video game revolution. You wouldn’t have thought so at the time, with its simple gameplay, rudimentary controls, some very low-end sounds, and a cannibalized TV for a display, but the legendarily stuffed coinboxes tell the tale. Fast forward 50 years or so, and Pong has been largely reduced to a programmer’s exercise to see how few lines of code can stand in for what [Ted Dabney] and [Allan Alcorn] accomplished. But now even that’s too much, as OpenAI Codex can generate a playable Pong from just a few prompts, at least most of the time. Continue reading “Let Machine Learning Code An Infinite Variety Of Pong Games” →

MicroPython ESP32 IDE Makes Life Simpler

February 7, 2023 by Al Williams 49 Comments

In theory, using MicroPython on the ESP32 is easy — just flash an image and connect using a serial port. But that leaves a lot of things you still have to do. You need to move files between the two platforms. You’ll want to manage network configurations. You might want better editing and assistance, too. So there are a number of IDEs made to help you and one we recently noticed was MPY-Jama.

The IDE provides source code editing, of course. But it also allows you to do things like pull information about the network using a dashboard or connect to a WiFi network easily. You can even create your own AP with a simple interface.

Although the front part of the README mentions it is for Windows or Mac, if you scroll down you’ll find instructions for installing under Linux. The IDE is extensible using “Jama Funcs” and can handle the flashing operation from inside the IDE.

Of course, there is an IDE from Arduino (but not the Arduino IDE) that handles MicroPython. You can also find a rundown of several similar alternatives online. If you need some inspiration for a MicroPython project, perhaps you’d like to play a game?