{"id":13303,"date":"2017-04-24T14:14:11","date_gmt":"2017-04-24T18:14:11","guid":{"rendered":"http:\/\/embedded-lab.com\/blog\/?p=13303"},"modified":"2018-06-13T23:32:37","modified_gmt":"2018-06-14T03:32:37","slug":"starting-stm8-microcontrollers","status":"publish","type":"post","link":"https:\/\/embedded-lab.com\/blog\/starting-stm8-microcontrollers\/","title":{"rendered":"Starting STM8 Microcontrollers"},"content":{"rendered":"

STM8 microcontrollers are 8-bit general purpose microcontrollers from STMicroelectronics (STM)<\/strong>. STM is famous mainly for its line of 32-bit ARM Cortex microcontrollers \u2013 the STM32s. STM8 microcontrollers are rarely discussed in that context. However, STM8 MCUs are robust and most importantly they come packed with lots of hardware features. Except for the ARM core, 32-bit architecture, performance and some minor differences, STM8s have many peripheral similarities with STM32s. In my opinion, STM8s are equally or sometimes more matched than the popular PICs and AVRs in all areas. Unlike PICs and AVRs however, I have seen STM8s mostly in various SMD packages. Only a handful of STM8 chips are available in Plastic Dual-Inline Package (PDIP)\/through-hole packages. I think it is a big reason for which most small industries and hobbyists don\u2019t play with them as much as with other 8-bit families. People like to setup their test projects in breadboards, trial PCBs or strip-boards first, prototype and then develop for production. To cope with this issue, STM has provided several affordable STM8 Discovery (Disco) boards to get started with. Besides there are many cheap STM8 breakout-boards from China.\"STM8S003K3<\/a><\/p>\n

<\/p>\n

I have experience playing with AVRs, PICs, 8051s, STM32s, MSP430s, TivaC and so on. To be honest, I thought learning about STM8 micros is a pure waste of time and energy. The learning curve will be steep. Things and tools would be different and thus difficult. However, gradually I found these MCUs very useful and there is literally no complexity at all. The main drive factor for learning STM8s is the price factor. They are very cheap. When it comes down to other things, I have not found any book on STM8s written in English. There is literally no 100% complete blog post on the internet that shows the basics. Similarly, same story with tools. I have been using MikroC for AVRs, 8051s and ARMs and it is my favourite but at the time of writing, there\u2019s no MikroC compiler for STM8 family. I have also not stumbled upon any Arduino-like IDE that supports STM8 micros. Arduino-based solutions are also not my favourite as they don\u2019t go deep and have several limitations. Maybe it is not my luck. After much study and search, I found out that there are a few C compilers for STM8s. However, any new tool is both different and difficult at first. It is not always easy to adapt to new environments. You may never know what unanticipated challenges and harshness a new environment may throw at you even when you reach certain levels of expertise. I also don\u2019t want to use any pirated software and so a free compiler was a major requirement. I found out ST Visual Develop and Cosmic COSC compiler are both free tools. Cosmic used to be a paid tool but now it is absolutely free. The only easy thing till then was buying the STM8S Value Line Discovery board for just a few dollars and downloading the stuffs.<\/p>\n

The STM8 Family<\/span><\/h2>\n

There are over a hundred STM8 microcontrollers available today. The STM8 family can be simplified into three categorical groups as shown below.\"STM8<\/a><\/p>\n

There are subgroups within these groups but broadly speaking these three groups are what by which we can define the entire family. STM8S micros are general purpose robust and reliable micros that can be employed in almost all scopes. This is the most commonly used group and in fact we will be exploring it in this article. They are also cheap and smart. The second group \u2013 the STM8A family is intended mainly for automotive industries. This group is packed with additional hardware interfaces like CAN and LIN that are musts according to present-day automotive industry doctrine. The STM8As are also very versatile and are designed to withstand the harsh extremes of an automobile. For instance, STM8As can withstand high temperatures, in excess of 100\u00b0C. The last group consists of STM8L micros which are crafted for low power or battery-backed applications. Virtually they consume no power in idle mode. Thus, if you need high power savings or energy cuts in your projects, this group is the right choice. There are also low power editions of automotive-standard STM8 micros that are labelled STM8AL. Apart from all these there is also one variant of STM8 micros that are specifically designed for capacitive touch applications. These are called STM8Ts.<\/p>\n

The features and benefits of STM8 micros are numerous and can\u2019t simply be expressed in few words. The more you explore, the more you will know. STM8s can be powered with 3.3V or 5V DC power supplies and have built-in brownout detection circuitry. The low power editions can operate at much lower voltages than these values. Official STM8 Discovery boards come with voltage selection jumpers to allow users to select operating voltage level as required. There is very minimum risk of program corruption due to EMI or some other similar unprecedented factors. There is a fail-safe security system for the clock system which ensures that a system based on a STM8 micro won\u2019t stop working or get stuck up should its external clock source fail. All internal hardware possesses more features than any other competitive 8-bit microcontroller families that are widely available in the market. The best part is the price benefit. You pay less for most. All these features are well-suited for extremely harsh industrial environments. STM8s are designed with maximum possible combinations of features. Beyond your wildest wet dream, there are many extraordinary stuffs waiting to be unboxed.<\/p>\n

<\/p>\n

Overview of the Discovery Board<\/span><\/h2>\n

For getting started with STM8s, STM has provided several STM8 Disco boards. There are also other third-party boards too. However, I strongly recommend Disco boards for learning and experimental purposes. There are several reasons for this recommendation. One main reason is the fact that all Disco boards come with on-board detachable ST-Link programmers and they are extremely cheap. Shown below is the top layout of a STM8S discovery board.<\/p>\n

\"Layout\"<\/a><\/p>\n

The board I mostly used here in this article hosts a STM8S003K3T6 micro. It is a 32-pin entry-level microcontroller with 8kB flash memory, 1kB RAM and 128-byte true data EEPROM. It comes with some additional hardware \u2013 a LED connected to PD0 and a push button connected to PB7. Just as I stated before it also houses a detachable ST-Link V2 programmer. However, I don\u2019t recommend separating the programmer from the whole package. The board also has a prototyping area should one needs to prototype something. The overall board has a small form-factor and is a bit longer than a standard credit card. There are several other similar and popular STM8 Discovery boards like the STM8S105 Discovery.<\/p>\n

\"STM8S105<\/a><\/p>\n

There are also bulks of cheap Chinese minimum system STM8 development boards hosting different STM8 chips. Overall the boards and the chips are so cheap that many simple cheap gadgets from China are based on STM8 MCUs.<\/p>\n

\"Cheap<\/a><\/p>\n

Some cheap STM8-based simple products are shown below:<\/p>\n

\"Products\"<\/a><\/p>\n

The first one is a cheap DIY LC meter LC-100A. The other one is a simple DC panel meter. These are just simple examples. There are many industrial and sophisticated products based on STM8 micros.
\n<\/p>\n

Hardware Tools<\/span><\/h2>\n

The list of hardware tools needed is not very long.\u00a0 We will obviously need a STM8 board and I prefer a Discovery board over any other board since it comes with a built-in ST-Link programmer\/debugger hardware. If you have some other board like the ones I already showed, you will need a ST-Link programmer. I recommend an additional ST-Link programmer apart from the one available on board.<\/p>\n

\"ST-LINK\"<\/a><\/p>\n

ST-Link programmers\/debuggers communicate with target STM8 micros via SWIM interface. This interface is the standard for all STM8 micros. Basically, it is a four-wire interface with two wires (VDD and GND) being used for powering the target. The rest two are reset I\/O and SWIM I\/O. In the official ST-Link V2 programmer unlike other ST-Link programmers, there is a dedicated port for SWIM interface with STM8 inscribed near it. Cheap USB thumb drive-sized ST-Links are also available in the market. They are portable and as good as the official ones. You can also DIY your own ST-Link programmer as the design for it is open source.<\/p>\n

\"SWIM<\/a><\/p>\n

Apart from these we will also require some basic electronic lab stuffs like a USB-to-serial converter, connecting\/jumper wires, LEDs, buttons, various types of sensors, etc. that are typically found in a common Arduino starter kit.<\/p>\n

\"Arduino<\/a><\/p>\n

It is yet better if you have either a logic analyser or oscilloscope. A good digital multimeter (DMM) and a well-regulated DC power supply\/source are must haves. You can also use a cell phone charging power bank as a power source since Disco boards have USB ports.<\/p>\n

\"Saleae<\/a><\/p>\n

<\/p>\n

Software Tools<\/span><\/h2>\n

Just like any other software developer, my choice of language for software development is C language. I don\u2019t want to spend time coding complex stuffs in assembly or other languages. STM8s are also C optimized micros. Apart from these reasons, I chose C language for the fact that STMicroelectronics has provided a Standard Peripheral Library (SPL)<\/em><\/strong> that is very easy to use. With SPL, it becomes totally unnecessary to program each peripheral register with meaningless numbers and maintain coding sequence. We will never need to access registers for any reason as everything is done under the hood of SPL. All sequences are dealt inside the SPL. All that we will ever need is the clear concept of each hardware block, their working principles, their capabilities and limitations.<\/p>\n

We will need an Integrated Development Environment (IDE)<\/em><\/strong> and a C-language toolchain. The best stuffs you can get your hands on at zero costs are ST Visual Develop (STVD)<\/em><\/strong> IDE and Cosmic <\/em><\/strong>C compiler. Both are free but a rather difficult to use at first. STVD also packs with a programmer software tool called ST Visual Programmer (STVP)<\/em><\/strong>. We will need STVP to upload codes to target STM8 micros.<\/p>\n

Cosmic used to be a paid tool just like your PC\u2019s antivirus software but at the time of writing this article, the Cosmic team has made it absolutely free for STM8 family. However, to use it you will need to register and acquire a license key via email. Usually this procedure of acquiring license and registration is maintained automatically by the software company\u2019s server but with Cosmic it is different story. You will need to wait for some guy at Cosmic end to respond to your license request. It may take a few minutes or even a day but still the best part is getting a full version compiler for nothing.<\/p>\n

\"STVD\"<\/a><\/p>\n

You can get
\nSTVD from here: http:\/\/www.st.com\/en\/development-tools\/stvd-stm8.html<\/a> and
\nCosmic C compiler from here: http:\/\/www.cosmic-software.com\/download.php<\/a>.<\/p>\n

You need to register in order to download both software. For Cosmic you will also need to acquire a free license for it work. So just fill in some basic info about you.<\/p>\n

\"COSMIC<\/a><\/p>\n

Firstly, we will need to install STVD. Installation procedure is simple and same as typical software installation. Just click next, next and next. After that we will need to install Cosmic C compiler. Again, just next, next and next until the screen as shown below.<\/p>\n

\"COSMIC<\/a><\/p>\n

After installation, you\u2019ll prompted for licence. You must register your license unless you have already registered. If you have already registered, then you\u2019ll be asked if to overwrite registration. You should skip reregistering.<\/p>\n

\"COSMIC<\/a><\/p>\n

For the first run, you\u2019ll get the following screen looking for a valid license.<\/p>\n

\"COSMIC<\/a><\/p>\n

You must fill all the starred (*) points to complete the process of registration. Select \u201cWrite to File\u201d<\/em><\/strong> option and save the file as a text (.txt) file. The file name should be \u201cCM8_license.txt\u201d<\/em><\/strong>. Send this file to stm8_Free@cosmic.fr<\/a> with subject \u201cSTM8FSE, STM32 32K License Request\u201d<\/em><\/strong>. Now you\u2019ll need to wait for the Cosmic team to respond to you. They\u2019ll send you an email back with an electronic key license. The file will have a name like \u201clicense.lic\u201d<\/em><\/strong> and the email will have some instructions.<\/p>\n

This was my emailed license.<\/p>\n

\"Email\"<\/a><\/p>\n

Once you get the license, you\u2019ll need to show the software its location and complete the licensing process as shown below. Save the license file in a secured location.<\/p>\n

\"COSMIC<\/a><\/p>\n

<\/del>\"COSMIC<\/a><\/p>\n

\"COSMIC<\/a><\/p>\n

At the end of this process, we can enjoy the compiler without any limitations.<\/p>\n

I also recommend that you download Sublime Text (https:\/\/www.sublimetext.com\/<\/a>) or Notepad++ (https:\/\/notepad-plus-plus.org\/<\/a>) for viewing your code with ease. These are very cool software. This is not mandatory though.<\/p>\n

\"Code\"<\/a><\/p>\n

<\/p>\n

STM8CubeMX<\/span><\/h2>\n

Should I or should I not feel fortunate was my question at the time of writing this article and that\u2019s because STM8CubeMX was released in late February 2017. Yes, that\u2019s the time when I was compiling all these STM8 stuffs together. Prior to that I was wondering about a software similar to STM32CubeMX but for STM8s. Back then, I could not find one and raw documentations were only helpers. Although it is still in its early stages of development and still not as robust as its STM32 cousin in terms of code generation capabilities and other areas, we can expect great innovations in the near future. It reminds me of the early days of STM32CubeMX. Not everyone expected it to overcome all the challenges in a very short period of time.\u00a0 At present, we can use STM8CubeMX for common info on STM8 chips like pin assignments\/mapping, basic technical specs like memory capacities, possible clock configurations, etc. I can just wonder the potential future integrations and bug fixes. Power consumption calculator is one such tool hopefully to be integrated. STM, most likely, has some serious big plans for it. Nevertheless, we must thank STM for this cool software.<\/p>\n

Visit http:\/\/www.st.com\/en\/development-tools\/stm8cubemx.html<\/a> to download.<\/p>\n

\"STM8CubeMX\"<\/a><\/p>\n

I recommend using it only as reference for now. Don\u2019t make yourself dependent on it. There are still many bugs fixes that are yet to be addressed. One example is as in the above screenshot. Notice Timer 4 (TIM4) is missing although STM8S003 micros have this timer. I\u2019m pretty sure the software developers are working hard on such silly issues. For now, it is more like a promise of good tidings to come. This is why I haven\u2019t included it in the \u201cmust-have\u201d software list and wanted it to be discussed separately.<\/p>\n

<\/p>\n

Preparing the Software Tools<\/span><\/h2>\n

Firstly, we need three major documents before starting to program STM8 micros. These are as follows:<\/p>\n

    \n
  1. STM8 Reference Manual.
    \n    http:\/\/www.st.com\/content\/ccc\/resource\/technical\/document\/reference_manual\/9a\/1b\/85\/07\/ca\/eb\/4f\/dd\/CD00190271.pdf\/files\/CD00190271.pdf\/jcr:content\/translations\/en.CD00190271.pdf<\/a><\/li>\n<\/ol>\n
      \n
    1. Datasheet of the MCU (STM8S003<\/em><\/strong>) that we\u2019ll be using.
      \n      http:\/\/www.st.com\/content\/ccc\/resource\/technical\/document\/datasheet\/42\/5a\/27\/87\/ac\/5a\/44\/88\/DM00024550.pdf\/files\/DM00024550.pdf\/jcr:content\/translations\/en.DM00024550.pdf<\/a><\/li>\n
    2. STM8SVLDiscovery Board User Manual.
      \n      http:\/\/www.st.com\/content\/ccc\/resource\/technical\/document\/user_manual\/c8\/37\/11\/ba\/b5\/e7\/4c\/ee\/DM00040810.pdf\/files\/DM00040810.pdf\/jcr:content\/translations\/en.DM00040810.pdf<\/a><\/li>\n<\/ol>\n

      These docs will be needed everywhere during learning session. The reference manual states the use and purpose of all the hardware blocks in details. It includes register descriptions, naming conventions, modes of operation of all hardware, etc. However, it does not specify the specifications of a given STM8 micro and that\u2019s because it is a generalized literature for all STM8S and STM8AF micros. As we know even within a family of micros, one MCU differs from another in many aspects. Most commonly this variation comes in the form of memory capacities and I\/O pin counts. Sometimes electrical specs also vary and so to know the limits and general specs of our target MCUs we need to checkout their respective datasheets. Lastly the Discovery board user manual is most useful for the hardware schematics, pin assignments and layouts. If you are using some other board then I suggest that you acquire at least its schematic.<\/p>\n

      Now with Cosmic, STVD and STVP installed our software tool setup is almost ready. There are two approaches to STM8 programming. The first uses the traditional concepts of register-access-based coding, meaning you\u2019ll have to set up every register on your own. The second way utilizes a specialized method of coding by using standard libraries developed by STM that are both universal and platform independent, meaning your C code will be same for any compiler using these libraries. These libraries are called Standard Peripheral Libraries (SPL)<\/em><\/strong>. With these libraries, no one will ever need to get down to register-level access. The libraries are so coded that a coder will only have to know his\/her chips\u2019 hardware specs and some basics of these hardware. On the coding part, he\/she will only have to set properties and desired values. The SPL manages the rest. For instance, when setting up a UART, we will only need to set interrupts, IOs and UART properties like baud rate, parity, etc. All of these setups are done with meaningful numbers and texts.<\/p>\n

      The STMicroelectronics Standard Peripheral Libraries (SPL) for STM8 microcontrollers can be found here: http:\/\/www.st.com\/en\/embedded-software\/stsw-stm8069.html<\/a>.<\/p>\n

      I wrote this article using SPL since it will be ridiculous to code STM8s using the old-fashioned way of configuring registers one-by-one manually. Thus, it is a mandatory download item. You should preserve and retain the downloaded SPL zip file fully intact. You may need it when things get messy.<\/p>\n

      Now make two folders and name them \u201cinc\u201d<\/em><\/strong> and \u201csrc\u201d<\/em><\/strong>. The \u201cinc\u201d<\/em><\/strong> folder will be filled with all the header files (\u201c.h\u201d<\/em><\/strong> extension files) from the extracted zip file. Similarly, the \u201csrc\u201d<\/em><\/strong> folder will be holding the source files (\u201c.c\u201d<\/em><\/strong> extension files). For ease of work, it is better to keep these folders secured just like the SPL zip file because every time when we will be making new projects the files in these folders will be needed. You can copy these files to your project folder or you can keep it centrally somewhere. I prefer the former method as doing so will not have any conflicting issue with other projects needing modifications. However, it will cost hard-drive space. This method is however less confusing and trouble-free for beginners. Extract all the files as shown below:<\/p>\n

      \"Source<\/a><\/p>\n

      Note that there are more header files than source files. This is because there are two extra header files \u2013 stm8s.h <\/em><\/strong>and stm8s_conf.h <\/em><\/strong>that define processor type and processor properties. To make things work, we will have to comment one line of the stm8s_conf.h<\/em><\/strong>. You will find a line at the bottom of this file written as:<\/p>\n

      #define USE_FULL_ASSERT\u00a0\u00a0\u00a0 (1)<\/em><\/strong><\/span><\/pre>\n
      You need to comment or disable this line, otherwise the compiler will throw tons of error messages.\u00a0 Always check this at the start of a project. Surely, we don\u2019t want to assert our code.<\/p>\n
      Creating a New Code Project<\/span><\/h2>\n
      Assuming that STVD, STVP and Cosmic are properly installed, we will see how to create a new project.<\/p>\n