FreeRTOS tutorial on STM32

A High-density line of STM32 microcontrollers has quite a bunch of features that can be used in your programs. However, the more features you add to the source, the more complicated the program becomes, and it may become challenging to keep up with all things. Relying on the main loop and interrupts becomes a time-consuming task to manage. If you do not want to struggle while tuning things up manually, you can use one of the best free real-time operating systems (RTOS). It is handy when you need many separate functions to run in parallel without missing a task. RTOS scheduler takes care of giving each task a required period to perform. There are many great RTOS systems around. Many of them are free and open source. Follow the FreeRTOS tutorial to see how easy it is to run complex tasks. I love using FreeRTOS, which has a long successful history and is flexible to fit multiple types of hardware. You can check out my demo FreeRTOS tutorial on Atmega128. I also encourage you to give a try for other RTOS systems like ChibiOS, BeRTOS, and others. FreeRTOS is quite simple and easy to use. It has practically all of…

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Flashing programs to STM32. Embedded Bootloader

Post updated with new screens and up-to-date information (2019)! There have been several requests from users to explain more about loading programs into the flash memory of STM32 microcontrollers. There are several ways on how to perform stm32 flash programming. You may enter the STM32 bootloader directly via USART interface and upload the binaries. The more advanced and flexible method is to use an ST-LINK utility – an ST-based adapter, which connects to STM32 board through JTAG interface. Many ST development boards already have this feature included. Otherwise, you can jump-wires from one to another, or get a dedicated portable ST-Link adapter. Also, you can use standard third-party JTAG tools such as J-Link. Finally, you can flash your bootloader that works with any interface (USART, USB, SPI, etc.) The STM32F103RB board Any of these methods are great if they get the job done. In this topic, let us focus on how to perform STM32 flashing by using a bootloader. Today probably, no manufacturer is producing developing boards with RS232 interface. Nevertheless, you like me, probably have a dozen older boards with a serial port. They are great boards still to use in many projects.

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Setting up CoIDE with GNU tools

For some time I’ve been using Codebench ARM GCC tools for developing software for ARM microcontrollers. As IDE I used plain Eclipse which I had to configure by myself. It worked pretty well, and there is nothing wrong with this. Anyway, sometimes it gets a little annoying to keep an eye on configurations and manual settings. So I decided to give a try CooCox IDE which claims to be free and open. It seems that already supports all the microcontrollers I like to use. Along to this change, I am also moving to a different GCC tool collection. Codebench free tools are great, but on another hand, there are some limitations. One of them is release times. They are releasing their free tools twice a year, so updates and other improvements cannot reach as fast as you’d expect. Another thing I am concerned – disabled hard float functionality. If you would like to ta take advantage of floating point unit in Cortex-M4, then you get stuck. If you are not using hardware floating point module, then this tool works fine, and you can stick with it. Anyway, I don’t like limitations, especially with free tools, so I am switching to…

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Bit Band operations with ARM Cortex microcontrollers

I got few questions from our readers about the bit-band feature in ARM Cortex microcontrollers. It may seem to be a prominent topic, still may lead to come confusion while using bit-banding. So let’s look at this feature a little bit closer. Why use bit band Simply speaking Bit banding method allows performing atomic bitwise operations to memory areas. Why use bit banding? The most straightforward answer is because ARM Cortex doesn’t have something like BIT CSET or BIT CLEAR commands like most of the 8-bit microcontrollers do. So this is somewhat a workaround solution. Another question may rise – Why not using the read-modify-write method? Again this method is not reliable in some cases. For instance f there is an interrupt during this operation it can cause data corruption. Other situation may occur in embedded OS when different tasks may modify the same memory location. So we want a method that allows setting or clear individual bits with a single instruction. This is where the bit band method helps.

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Setting up Tiva C Launchpad project template with Sourcery Codebench and Eclipse

Tiva C series TM4C123G (MCU:TM4C1233H6PM)Launchpad is updated version of Stellaris Launchpad LM4F120 (MCU: LM4F120H5QR). Practically this is due TI’s choice to change name of product line. Such action led to some confusion especially for software developers. This means that software libraries had to be renamed, software tool adapted and so on. Since this work is most renaming things from one point this is easy task, from another point it may be tricky to check all corners. So if you just in to Texas Instruments ARM Cortex microcontrollers, it is better to start with Tiva C series and forget Stellaris. Otherwise this might get confusing to switch from one to another. At the moment TivaWare 1.1 still has some issues due to migration, but most things sould work fine. So lets try to create a project template for Eclipse IDE and Sourcery Codebench Lite GCC compiler tools. First you need to download and install Eclipse with CDT C/C++ tools (Eclipse Indigo includes this). Next you need to install latest Mentor Sourcery Codebench Lite. Also download and extract TivaWare for C series, where all libraries and examples are located. In order to Flash microcontroller download LM Flash Programmer. Other materials and introduction…

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How to calibrate touch screen display on STM32 board

stm32_touch_screen_interface

Touch screen displays are common choice in many microcontroller projects. Touch capability won’t take additional space – it sits on top of LCD where you can directly interact with objects you see on screen. In order to get this working touch screen coordinates must match screen coordinates. So could be sure when you touch the point on screen you point where you want. Touch screen is analog device. It is made of two flexible resistive sheets with gap between. When screen is touched, a connection between sheets is made and thus measurement of voltage drop is taken. Normally resistive touch screen has four wire configuration. And normally there is a specialized IC used to take measurements and send data to MCU for processing. In our case we are dealing with ADS7843 touch screen controller, but in other systems this works pretty same way. The fact is that touch screen controller reads screen ADC values and simply passes them via SPI interface. So all you get is raw ADC readings that are not lined up with LCD coordinates. As you know LCD screens can be different resolution, different orientation, so data gathered from resistive touch screen must be scaled down to…

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Learn Arm Cortex processor the easy way

The Definitive Guide to the ARM Cortex-M3 Second Edition

Me, like most of you have been using smaller scale microcontrollers like AVR or PIC. These are great chips and you should keep working with them as long as they fit your needs. Eventually you getting to project where your loved chip simply cannot handle the load. You need to run more complex code to do fancy things; You must keep up with more complex interfaces; Meet multimedia challenges; Process more data in a shorter time. Eventually you realize that you simply need faster and more modern microcontroller to work with. ARM Cortex is a number one choice. Like with all new stuff you may find it a bit frightening to start with new microcontroller. When I first started with ARM Cortex-M3 processor I was looking for some basic and easy to understand guide. I found and highly recommend a wonderful book about ARM Cortex-M3 CPU. Its called [The Definitive Guide to the ARM Cortex-M3, Second Edition]. This is great book written by Joseph Yiu. Why start with a book, instead of hunting for scattered tutorials on the internet? Especially if you haven’t tried to work ARM microcontroller you may miss lots of features it has comparing to 8-bit micros.…

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