BIVBlog (Benedikt's IT Video Blog)

Feeding analog voltages to digital microcontroller inputs already got us some interesting effects, but what about leaving an input pin entirely disconnected? All of a sudden microcontrollers become sensitive to the weather outside, and the clothes we wear—or any other source of electrostatic.

The easy way to deal with this is to always ensure that an input is always fed a proper input voltage. But if we want to use a “single throw” (or “connect—disconnect”) type of switch or pushbutton, then we have to use a simple, high value resistor as a “pull-up” or “pull-down” resistor.

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While digital inputs on microcontrollers are meant to be fed digital input signals, what will actually happen if we feed them a real world input voltage? And what is a Schmitt Trigger, and what is it good for anyway?

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Reading basic digital input with a microcontroller is fairly straightforward—at least as long as you really keep things simple and don’t do some of the advanced stuff following in the next few episodes.

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Following up on the previous episode (BIVBlog #46: Bitwise Operators in C (not only) for Microcontrollers) I explain ways to minimize the pain involved with the bitwise operators in C. While none of the shown approaches are perfect, and some are plain counterproductive, there are ways to keep your code easy to understand, modify, debug and maintain.

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While bitwise operators are a core feature of the C language for anyone doing low level programming, people who know C mostly from application development sometimes struggle to come to grips with them. This quick primer explains some idioms commonly seen with microcontrollers as well as any other low level C programming.

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Part of the fun of playing around with microcontrollers is the actual building of electronic gadgets. The good news is it takes less skills, tools and money to actually get things done than what you need for a full-blown general purpose electronics lab.

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As useful as the various pre-made evaluation target boards were to get our microcontroller development toolchain up and running, they are starting to become a burden. Dropping them now, and dealing with everything they have taken care of for ourselves so far, makes a lot of sense in the long run: It gives us more options with regard to microcontroller models and peripherals we can connect. Aside from that, bare components and a breadboard are usually cheaper than the equivalent evaluation board, so this may even save us a couple bucks.

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As useful as Makefiles are, a lot of people are mortally afraid of them. Admittedly, their syntax is somewhat quirky, and not knowing in advance in what exact order during execution may seem somewhat disconcerting, but they are an invaluable tool not only in multi-file projects but also whenever you want to compile programs in a reproducible—and convenient—manner.

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