Teaching people efficiently isn’t limited to transmitting material from one head to another — it’s also about conveying the principles that got us there. [Mara Bos] shows us a toolkit (Twitter,
nitter link) that you can arm your students with, creating a small playground where, given a set of constraints, they can invent and figure communication protocols out on their own.
This tool is aimed to teach digital communication protocols from a different direction. We all know that UART, I2C, SPI and such have different use cases, but why? Why are baud rates important? When are clock or chip select lines useful? What’s the deal with the start bit? We kinda sorta figure out the answers to these on our own by mental reverse-engineering, but these things can be taught better, and [Mara] shows us how.
Gently guided by your observations and insights, your students will go through defining new and old communication standards from the ground up, rediscovering concepts like acknowledge bits, bus contention, or even DDR. And, as you point out that the tricks they just discovered have real-world counterparts, you will see the light bulb go on in their head — realizing that they, too, could be part of the next generation of engineers that design the technologies of tomorrow.
Continue reading “Boards For Playful Exploration Of Digital Protocols”
Although protocols like I2C and SPI are great for communicating between embedded devices and their peripherals, it can be a pain to interface these low-level digital interfaces to a PC. [Alexandre] typically used an Arduino to bridge between the PC and embedded worlds, but he got tired of defining a custom serial protocol for each project. Inspired by MicroPython’s machine module, [Alexandre] has developed u2if—an implementation of some of MicroPython’s machine module for PC—using a USB-connected Raspberry Pi Pico to bridge between a PC and low-level digital interfaces.
u2if consists of two parts: the PC portion is a Python implementation of a portion of the MicroPython machine module, and the Raspberry Pi Pico receives some custom C++ firmware. Thus far, [Alexandre] has implemented functionality for the onboard ADCs, I2C, SPI, UART, and GPIO lines as well as additional support for I2S sound and the WS2812B addressable LED.
In addition to the u2if package, [Alexandre] has designed a PCB to break out all of the Raspberry Pi Pico’s interfaces in a handy 3×3.9″ board. We especially like that multiple headers are supplied for I2C, including one with enough space to mount an SSD1306 OLED display.
We think this could be an incredibly useful tool, and what makes it even more impressive is that it uses a board many of us already have laying around. If you want a dedicated device for interfacing with low-level digital buses, you may want to check out the GreatFET.
Many readers will be familiar with interfacing I2C peripherals. A serial line joins a string of individual I2C devices, and each of the devices has its own address on that line. In most cases when connecting a single device or multiple different ones there is no problem in ensuring that they have different addresses.
What happens though when multiple identical devices share an I2C bus? This was the problem facing [Sam Evans] at Mindtribe, and his solution is both elegant and simple. The temperature sensors he was using across multiple identical boards have three pins upon which can be set a binary address, and his challenge was to differentiate between them without the manufacturing overhead of a set of DIP switches, jumpers, or individual pull-up resistors. Through a clever combination of sense lines between the boards he was able to create a system in which the address would be set depending upon whether the board had a neighbour on one side, the other, or both. A particularly clever hack allows two side-by-side boards that have two neighbours to alternate their least significant bit, allowing four identical boards each with two sensors to be daisy-chained for a total of eight sensors with automatic address allocation.
We aren’t told what the product was in this case, however it’s irrelevant. This is a hardware hack in its purest sense, one of those which readers will take note of and remember when it is their turn to deal with a well-populated I2C bus. Of course, if this method doesn’t appeal, you can always try an LTC4316.