Section 1 Introduction to the AT91SAMD20 and the Development Environment

Section 1 Introduction to the AT91SAMD20 and the Development Environment Tasks In this section you will learn: The basics of the core you will be working on AT91SAMD20 and its features The basics of the development environment Atmel Studio 6 How to connect to the target via Studio 6.1 and load the binary to the target 12/02/13

Table of Contents 1. Introduction to the Core...1 2. The Evaluation Kit...2 2.1 Power Considerations... 3 2.1.1 Power Consumption Measurements... 3 3. Atmel Studio 6.1...3 3.1 Installing Atmel Studio 6.1... 4 3.2 Working with a Studio 6.1 Project... 6 3.2.1 Launching an Example Project... 6 3.2.2 Studio 6.1 IDE Components... 7 3.2.2.1 Project Folder/File Structure... 8 3.2.2.2 Menus... 11 3.2.2.3 Device Programming Tool... 12 3.2.2.4 Debugging Windows... 13 3.2.2.5 Project Properties... 14 3.2.2.6 Makefile... 17 3.2.2.7 Extension Manager... 18 3.2.3 Creating a New Studio 6 Project... 19 3.3 ASF Wizard... 19 4. Programming and Debugging the SAMD20 with Studio 6.1... 20 4.1 Connecting the Board... 20 4.2 Compiling and downloading... 21 4.3 Debugging Your Code... 22 5. Conclusion... 24 ii

1. Introduction to the Core The Atmel SAM D20 family of microcontroller is based on the ARM Cortex -M0+ 32-bit processor. It has the following salient features: CPU running at up to 48 MHz In-system, self-programming flash ranging from 16-256 KB and SRAM ranging from 2 to 32 KB Internal and external clock options with 48 MHz Digital Frequency Locked Loop SWD programming interface Peripherals such as Timers, ADC, DAC, Analog Comparators and Watchdog Timers Up to six Serial Communication Interfaces (SERCOM), individually configurable to operate as either SPI, TWI or USART Up to 52 programmable I/O lines Operating Voltage of 1.62 V to 3.63 V 64, 48, or 32 pin in TQFP or QFN package Figure 1 shows the block diagram of the microcontroller. Figure 1. Block diagram For detailed information on the microcontroller, please refer to the datasheet. Page 1 of 24

2. The Evaluation Kit The Atmel SAM D20 Xplained Pro evaluation kit houses the ATSAMD20J18 microcontroller and includes an on-board embedded debugger. Therefore, no external tools are necessary for programming or debugging. Some of its salient features are: 32 khz on-board crystal Micro-USB interface Virtual COM-port interface to target via UART Two mechanical buttons (user and reset button) One user LED 3 extension headers Two possible power sources Debug USB or External power source through the 4-pin power header marked PWR The SAM D20 Xplained Pro kit is fully supported by Atmel Studio 6.1 IDE. Several example applications for the kit are available as a starting point to develop user application. The IDE provides an easy platform to develop, program, and debug code for the SAMD20 target. More information on this is provided in Section 4. Figure 2. SAMD20 Xplained PRO Evaluation Kit Page 2 of 24

2.1 Power Considerations The power supply sources for SAMD20 Xplained Pro kit are shown in Table 1. Depending on availability, the kit will automatically make the necessary adaptation. Table 1. Power sources for SAMD20 kit Power input Voltage requirements Current requirements Connector marking External power 4.3 V to 5.5 V Recommended minimum is 500 ma to be able to provide enough current for extensions and the board itself. Recommended maximum is 2A due to the input protection maximum current specification. Embedded debugger USB 4.4 V to 5.25 V (according to USB spec) 500 ma (according to USB spec) PWR DEBUG USB 2.1.1 Power Consumption Measurements To measure current consumed by the SAMD20 microcontroller, replace the jumper on the current measurement header with an ammeter. This is shown in Figure 3. Figure 3. Current Measurement Header For detailed information on the evaluation kit, please refer to the User Guide. 3. Atmel Studio 6.1 Atmel Studio 6 is the integrated development environment (IDE) for developing and debugging Atmel ARM Cortex -M and Atmel AVR microcontroller (MCU) based applications. The Atmel Studio 6 IDE gives you a seamless and easy-to-use environment to write, build, and debug your applications written in C/C++ or assembly code. Atmel Studio 6 is free of charge and comes with a large library of 1600+ example projects. Page 3 of 24

With Studio 6, you can now enjoy Atmel Gallery and Atmel Spaces. Atmel Gallery is an online apps store for development tools and embedded software. Atmel Spaces is a cloud-based collaborative development workspace allowing you to host software and hardware projects targeting Atmel MCUs. Figure 4. Atmel Studio 6.1 3.1 Installing Atmel Studio 6.1 Studio 6.1 can be downloaded from the following site: http://www.atmel.com/tools/atmelstudio.aspx Click on the link as shown in Figure 5. You can choose the complete installer to install on a computer with no access to the internet. You will then be asked to fill a form as shown in Figure 6. You may choose to log in as a guest or create an Atmel account, if you don t already have one, and sign in as an Atmel user. Upon submitting the form, an email will be sent to the email address you provided with a link to the installer as shown in Figure 7. Run this installer. Page 4 of 24

Figure 5. Link to download Studio 6 The installer version at this time is 2730. This could be different during the time you attempt to download the installer. You may also have to download and install a patch to support newer hardware kits which is not required for the SAMD20 Xplained PRO kit. Figure 6. Download form Please provide a valid email address. A link to the installer will be emailed to this email address. Page 5 of 24

Figure 7. Installer link from email Installing Studio 6.1 may take several minutes depending on the speed of your computer. 3.2 Working with a Studio 6.1 Project In this section, we will learn the following: 1. How to launch an example project. 2. How to work with the IDE. 3. How to create a new project. 3.2.1 Launching an Example Project You can launch a new ASF example project from either the Start Page as shown in Figure 8 or the File Menu Option. The Start Page is available when Studio 6 is launched. It can also be accessed from View menu option. To open an example project, follow the steps below: 1. Click File > New > Example Project. 2. Select SAM D 32-BIT under Device Family as shown in Figure 9. 3. Select the required example project from one of the ASF versions. You may want to choose the most recent ASF version. 4. Provide the project name and location, then select OK. 5. Accept the software license agreement(s). The new example project will then be loaded. Figure 8. New example project Page 6 of 24

Loading the example projects may take several minutes the first time. Figure 9. Device family list Figure 10. Example project list 3.2.2 Studio 6.1 IDE Components The Studio development environment is broadly split into three areas as shown in Figure 11: 1. Atmel Studio Editor: Allows you to edit the source files 2. Solution Explorer: Allows you to explore the project source files 3. Output Window: Displays messages from the GCC compiler Page 7 of 24

Figure 11. Atmel Studio 6.1 IDE 3.2.2.1 Project Folder/File Structure An Atmel Studio Project folder will have the following file and 2 folders as shown in Figure 12: src folder: This folder contains all the project related source and header files. Debug/Release (or any other configuration the user sets up) folder: Upon compilation, this folder contains the map file, executables (.bin,.hex,.elf), binaries, a portion of the makefile, and all the object files..cproj file: The.CPROJ file, saved in XML format, stores all the references for your project including your compilation options. (There is also a.atsln file which stores information about projects that make up your solution.) Figure 12. Studio 6 project root folder in File Explorer Page 8 of 24

src folder: As already mentioned, all the source and header files of the project reside in the src/ folder. This folder will typically have the following items: main.c file (or the application specific file(s)) asf.h header file: This file includes all the API header files required by ASF for the modules you use in your project. It is automatically updated every time you add or remove drivers from your project using ASF wizard (ASF wizard is explained later). You should not manually edit asf.h asf folder: ASF folder: This folder contains the bulk of your project if you depend on ASF to generate code. All driver code imported to your project by ASF resides in this folder. config folder: This folder contains important configuration files such as conf_board.h and conf_clock.h o conf_board.h: This file is mainly used for specific board configuration. The conf_board.h file will allow the developer to define a conditional flag that enables or disables the GPIO to perform the required function in the project. o conf_clock.h: This file includes the definitions of the different clock configurations for the device (clock sources, prescalers, etc.). This is the entry point to configure the clocks used in the application. It is up to the user to change it based on need. The ASF folder contains a folder common to all projects, a folder for each family of microcontrollers, and a third-party folder for all ARM microcontroller projects. A description of each is given below: common folder: This folder contains a board.h header file that defines all the evaluation kits supported by Atmel Studio. It also contains a services and utils folder common to all projects. microcontroller specific folder: This folder contains the following: o boards folder: This folder contains a header file listing definitions specific to the target of the current project. For example, the samd20_xplained_pro.h header file. There is also a board_init.c file that contains a function called board_init that configures the GPIO pins for the different hardware peripherals. o drivers folder: This contains low level driver code to directly access the device registers. o utils folder: This contains utilities such as linker scripts, system calls, and preprocessor definitions. Another important folder inside the utils folder is the cmsis folder. This folder includes: Source file that contains the interrupt vector table definition and the startup code (for example, startup_samd20.c). Source file that contains the clock initialization code (e.g., system_samd20.c) include folder that contains system level header files pertaining to the microcontroller. For example, the top-level header file samd20.h which picks the header file of the microcontroller on the target board, e.g., samd20j18.h for the SAMD20Xplained PRO board. This header file contains the base Page 9 of 24

address definition for all the peripherals such as ADC, Timer Counter, etc. The include folder has sub-folders such as component, instance, and pio. component folder: This contains header files for each peripheral. Each header file defines a structure listing all the registers belonging to the corresponding peripheral. instance folder: This contains header files for each peripheral that lists the memory mapping for each register belonging to the corresponding peripheral. pio folder: This contains header files for each variant of the SAM microcontroller family, for example pio_samd20j18.h. These header files define the hardware pins and port definitions for each peripheral. thirdparty folder: This folder contains software with licenses other than Atmel license. For example CMSIS folder contains CMSIS library and header file with an ARM license. Figure 13 shows the ASF folder structure for a typical SAMD20 project. For more detailed information on ASF please refer to the following application notes: Atmel Software Framework Reference Manual (AVR4030) Atmel Software Framework Getting Started (AVR4029) Figure 13. ASF Folder Structure Page 10 of 24

3.2.2.2 Menus Studio 6 has a rich set of menu options as shown in Figure 14. The look and feel of the IDE is similar to Visual Studio. Therefore, most of the icons are standard options that are also found in Visual Studio, such as SAVE, SAVE ALL. The START DEBUGGING AND BREAK and START WITHOUT DEBUGGING icons are easily accessible. The current target and the debugger are displayed on the menu bar. Other important icons are shown in Table 2. Figure 14. Menu options Table 2. Studio shortcuts Icon Function Keyboard Shortcut Launch a New Example Project Ctrl+Shift+E Launch ASF Wizard Launch Solution Explorer Ctrl+Alt+L Launch Start Page Launch Extension Manager Launch Device Programming Window Ctrl+Shift+P Launch Command Window Ctrl+Alt+A Launch I/O View Window for Debugging Page 11 of 24

3.2.2.3 Device Programming Tool The Device Programming tool can be launched from the tools menu option. Figure 15 displays the device programming tool window. The different parts of the tool are explained below: A. Dropdown option to select the debugger such as SAM ICE debugger or on-board debugger. B. Dropdown option to select the device variant. C. Type of interface such as JTAG or SWD. D. Once the proper debugger, device variant, and interface are selected, clicking READ will display a unique device signature. E. The title bar displays the chosen debugger. F. Other options to the left of the tool are as follows: Memories: Allows you to erase the chip, select a pre-built.elf or.hex file and program it to the target. It also allows you to verify the flash after programming. Interface settings: It allows you to change the clock frequency of the debugger. Tool Information: Displays the debugger information such as firmware version, hardware version, etc. Device Information: Displays information of the device variant such as flash size, SRAM size, type of processor, etc. Security: This will allow you to set a security bit so as to disallow access through all external programming and debugging interfaces. Figure 15. Device programming tool Page 12 of 24

3.2.2.4 Debugging Windows Atmel Studio provides various debugging windows that are extremely useful. They can be accessed during debugging from the Debug menu option: Debug > Windows. Some important debug windows are: Breakpoints: This lists all the breakpoints that have been applied. They can be disabled while debugging as well. I/O View: This is an extremely important tool for debugging, shown in Figure 16. It shows the values of registers, including the value of each bit in the register and the memory location of the register. Processor View: This displays the value of some important register such as Program Counter, Stack Pointer, etc., as shown in Figure 17. Memory: Displays the contents of different parts of the memory such as Flash memory while debugging the flash. Figure 16. I/O View Page 13 of 24

Figure 17. Processor View 3.2.2.5 Project Properties The Project Properties Window can be accessed from the Project Menu: Project > <Project Name> Properties. From this window, you can set the following: Build: You can set different Build Options from here. You can choose to use an external Makefile or the default Makefile generated by Studio 6. You can create different Configuration such as Debug, Release or custom configurations each having different build options or compile/linker settings. Build Events: This allows you to set pre-build or post-build events such as running specific DOS commands. Toolchain: This is probably the most used feature from Project Properties. Here are all the options that can be set: o ARM/GNU Common Options (Figure 18): o Output file format such as.hex,.bin, etc. Output code format such as Thumb or ARM. ARM/GNU C Compiler Options: Here are a few commonly used settings: Symbols: You can set symbols to be defined and undefined for the current project. The icons on the top right of the defined symbols and undefined symbols window allow you to add new symbols, remove existing symbols, edit existing symbols and move an existing symbol up or down the list. (Figure 19) Directories: You can specify to the compiler the include paths of all the directories in the project. The icons on the top right of the window allow you to add new paths, remove existing paths, edit or move an existing path up or down the list. (Figure 20) Optimization: Allows you to set the optimization level. (Figure 21) Page 14 of 24

o ARM/GNU Linker Options: Here are some commonly used settings: Libraries: You can specify to the Linker all the libraries that need to be linked and also the path to the library. There are icons that allow you to add new library/library path, remove, edit or move an existing library/ library path. (Figure 22) Miscellaneous: You can specify other linker flags and objects such as path to the linker file. (Figure 23) Device: You can change the current device variant. Tool: You can choose a debugging tool that can be used with the target board. Figure 18. OutputFiles setting Figure 19. Symbols definition Page 15 of 24

Figure 20. Directory path setting Figure 21. Optimization level Figure 22. Linker Library settings Page 16 of 24

Figure 23. Miscellaneous Linker settings 3.2.2.6 Makefile Studio 6 generates a Makefile based on the project properties defined. All Studio 6 projects for SAM Microcontrollers contain a Makefile template in the ASF/SAM/utils/Make folder. This template is basically a script with a set of rules that is used to generate the Makefile. Please note that this is NOT the actual Makefile. The actual Makefile generated by Studio 6 using the template and the project properties can be found in the Debug or Release folder (or the custom configuration set) found in the root directory of the project as shown in Figure 24. Figure 24. Makefile generated by Studio 6 Page 17 of 24

3.2.2.7 Extension Manager Many additional extensions including libraries that may be useful are available for download from the extension manager. These provide enhanced features for a variety of projects. Most tools are free products from Atmel and third-party developers. To install an extension, simply choose your product and click Download, shown in Figure 25. You will be asked to log in to your myatmel account, shown in Figure 26. For new users, signing up is quick and easy. Figure 25. Extension Manager Figure 26. myatmel login Page 18 of 24

3.2.3 Creating a New Studio 6 Project We already know how to create a new project from the list of ASF example projects. However, if you want to create a new empty project for an Atmel evaluation kit or a custom board, Studio 6 will create a project template populated with minimal code complete with main.c, asf.h, and other header files. Here is how you create a new project: 1. Click File > New > Project 2. Under C/C++ choose ATMEL-BOARDS 3. Highlight SAM D20 XPLAINED PRO SAMD20J18 4. Give your project a name and then select OK Figure 27. New project setup 3.3 ASF Wizard Atmel Software Framework (ASF) allows easy design, evaluation, and prototyping of projects by providing the user a collection of embedded software, managed by the ASF Wizard. When designing, it is important to add necessary modules from ASF to your project. With your project opened, select ASF > ASF Wizard. The ASF Wizard window should be displayed with the list of the available drivers, services, and components, as shown in Figure 28. On the right side of the window, you can find the list of drivers already added in the project. On the left you can find all the drivers, services, and modules that are available to add. Page 19 of 24

Figure 28. ASF Wizard Window Modules can be found by either manually scrolling down the list or by using the search box. As an example, we will add a delay module to our project by typing the word delay in the search box, as shown in Figure 29. The Delay routines module appears as the result and we add this by highlighting the name of the module and then clicking ADD. The addition is not finalized until we select APPLY, after which a summary of changes is available for viewing. Figure 29. Adding modules in ASF Wizard 4. Programming and Debugging the SAMD20 with Studio 6.1 Once your project is ready, it is time to connect Studio 6.0 to the target, compile and debug. 4.1 Connecting the Board Connect the SAMD20 microcontroller to the PC via the mico-usb port as shown in Figure 30. Consider the power requirements as previously mentioned in Section 2.1. Page 20 of 24

Figure 30. Connecting the board 4.2 Compiling and downloading With our project ready for device programming, we can compile and download the firmware to the target using the following steps: 1. Click Build > Build Solution (or use shortcut F7) 2. Click Tools > Device Programming 3. Select the ATSAMD20J18 device and XPRO-EDBG tool, then click APPLY, as shown in Figure 32. 4. Under MEMORIES, the.elf file should be already selected for programming. Now click PROGRAM, as shown in Figure 33. Figure 31. Build solution Page 21 of 24

Figure 32. Set up device for programming Figure 33. Program device 4.3 Debugging Your Code To start debugging your code, you will need to first choose a debugger. With a project open, click No Tool and select XPRO-EDBG ATML1873040200003972 (These numbers will not be the same as they are the serial number found on your board) as shown in Figure 27. (Note that the interface will automatically select SWD.) Figure 34. Choosing the debugger Page 22 of 24

Many of the debugging features in Atmel Studio are commonly found in Visual Studio. Table 3 shows a list of functions from the toolbar. Table 3. Debug toolbar options Icon Function Shortcut Start Debugging F5 Start Debugging and Break Alt + F5 Stop Debugging Ctrl + Shift + F5 QuickWatch Shift + F9 Step Into F11 Step Over F10 Step Out Shift + F11 Run to Cursor Ctrl + F10 Reset Shift + F5 Disassembly Alt + 8 Registers Alt + 5 Memory 1 Alt + 6 Processor View I/O View Placing breakpoints in the code allows the program to run and pause while the user checks to see if the program is functioning correctly at any point. The process in Atmel Studio is exactly the same as it is for Visual Studio. Clicking on the left margin of the code places a breakpoint at that line. There is also the option of right clicking on any line of code and choosing Breakpoint > Insert Breakpoint. Page 23 of 24

5. Conclusion In this section we have covered a basic introduction to the SAMD20 core and the Atmel SAM D20 Xplained Pro evaluation kit. We have gone through the Atmel Studio 6 IDE in quite a detail. We are now familiar with the following: 1. How to launch example Studio 6 project and how to create a blank project. 2. The project folder/file structure 3. How to import code with ASF Wizard 4. The different components and features of the Studio 6 IDE and working with the IDE 5. How to compile and debug the project on the target In the next few chapters, we are going to learn the different peripherals available on the SAMD20 and we are going to write code to access and control these peripherals via Studio 6 projects. Page 24 of 24

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