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On PLAY Embedded you can find useful resources to get started with embedded systems: media, examples and accurate descriptions are also provided. Come on, learn by doing!

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Reading a Slider

Reading a Slider

Widely used in sound mixers, the slider can be used as input for many applications. There isn’t so much to say as this device is made by two potentiometers working together. Indeed, when the cursor slides, it changes the position of two side potentiometers.

The slider shown in Fig.1 has six pins:

VCC, (are two connected together) connected to power supply 3.0V DC; GND, (are two connected together) connection to ground; OTA, middle pin of potentiometer #1; OTB, middle pin of potentiometer #2.

We can sample both OTA and OTB making mean to better evaluate slider continue reading...

STM32, ChibiOS and a 8×8 LED Matrix

STM32, ChibiOS and 8x8 LED Matrix

The MAX7219 is a compact, serial input/parallel output common-cathode display driver. Included on-chip there are a BCD code-B decoder, the multiplex scan circuitry, segment and digit drivers, and an 8×8 static RAM that stores each digit. Only one external resistor is required to set the segments current.

This chip is often used to drive 7-segment display having up to 8 digits or up to 64 individual LEDs. It is not unusual find this chip in DIY kits to be mounted on a small PCBs like that used in this article (See Fig. 1).

This chip could be found in different packages continue reading...

Port a ChibiOS based application to another platform

Port a ChibiOS based application to another platform

We already talked about ChibiOS/HAL design and its multiple architectures support. This is very important for regular developers: imagine a scenario in which you design an application using a certain MCU and after a first stage you decide to upgrade your application. Imagine also that hardware resources on the MCU you decided to use are not enough to make that upgrade. At that point you have to port application on another MCU and this could cost a big effort in terms of time/money. If your application is ChibiOS based and you followed some guidelines already introduced in continue reading...

A Radio Frequency transceiver library: nRF24L01 and ChibiOS/RT

A Radio Frequency transceiver library nRF24L01 and ChibiOS/RT

The nRF24L01 is one of the most popular RF transceiver as it is very cheap and it could be found already configured on small PCBs with needed passive components. This means that only a MCU is needed to design a radio system with the nRF24L01.

The nRF24L01 is a highly integrated, ultra low power 2Mbps RF transceiver IC for the 2.4GHz ISM band. It provides an hardware protocol accelerator, the Enhanced ShockBurst, enabling the implementation of advanced and robust wireless connectivity with low cost MCUs.

By this article we want to provide a full library for nRF24L01 continue reading...

C Library design for embedded applications: tips and hints

C Library design: tips and hints

Write reusable code is one of the most powerful and time-saving thing that an embedded programmer should learn. Compose well-arranged libraries makes things easiest, especially when we want to add old code in a new project. Citing one of the most talented programmers I have ever met, “Well done code should be like a LEGO: must fit perfectly and without any effort”. So a good library should be quite abstract, with a simple hierarchy and should provide some well documented APIs.

Even if this is a generic embedded article, we will provide some concrete example.

When we want continue reading...