Create a project

Ok. No more chatting! Let us create our first project. We will create a simple application that makes the Nucleo LD2 LED (the green one) blinking.

Go to File->New->C Project. Eclipse shows a wizard that allows to create our test project (see Figure 6).

Figure 6: Project wizard - STEP 1

In the  Project name   field write   hello-nucleo  (your are totally free to choose the project name you like). The important part, indeed, is the  Project type  section. Here we have to choose the

Hello, Nucleo! 49 STM32 family of our Nucleo board. For example, if we have a  NUCLEO- F401RE  we have to choose STM32F4xx C/C++ Project , or if we have a NUCLEO- F103RB  we have to choose STM32F1xx C/C++

Project .

Unfortunately, Liviu Ionescu still has not implemented project templates for the STM32L0/1/7 and STM32F7²  families. If your Nucleo is based on one of these series, unfortunately you have to jump to the next chapter, where we will se a more general way to generate projects for the STM32 platform. However, it could be that by the time you read this chapter, the plug-in has been updated with new templates.

Now click on the Next button. In this step of the wizard is really important to select the right size of RAM and FLASH memory (if those fields do not match the quantity of RAM and FLASH of the MCU equipping your Nucleo, it will impossible to start the example application). Use the Table 1 to choose the correct values for your Nucleo board³.

Table 1: RAM and FLASH size to select according the given Nucleo

So, fill the fields of second step in the following way (see  Figure 7 for reference):

Chip Family: Select the Cortex-M core of the MCU equipping your Nucleo (see  Table 1).

Flash size: keep the right value from Table 1.

²A ST sales representative told me that a Nucleo-F7 will be released in the 2016, but at the moment there is no official announcement from ST.

³In case you are using a different development board (e.g. a Discovery kit), check on the ST web site for right values of RAM and FLASH.

Hello, Nucleo! 50 RAM size: keep the right value from Table 1.

External clock(Hz): leave this field as is, since all Nucleo boards do not provide an external crystal (HSE).

Content: Blinky (blink a LED).

Use system calls: Freestanding (no POSIX system calls).

Trace output: None (no trace output).

Check some warnings: Checked . Check most warnings: Unchecked.

Enable -Werror: Unchecked.

Use -Og on debug: Checked . Use newlib nano: Checked . Exclude unused: Checked .

Use link optimizations: Unchecked.

Figure 7: Project wizard - STEP 2

Those of you having a STMF3 Nucleo, will find an additional field in the wizard step. It is named CCM RAM Size (KB), and it is related to the Core Coupled Memory  (CCM). If you have a NUCLEOF334 or a NUCLEO-F303 board, fill the field with the value from  Table 1. For other STM32F3 based boards place a zero in that field.

Hello, Nucleo! 51 Now click on the   Next   button. In the next two wizard steps, leave all parameters as default.

Finally, in the last step you have to select the GCC tool-chain path. In the previous chapter, we have installed GCC inside the ^∼/STM32Toolchain/gcc-arm  folder (in Windows the folder was C:\STM32Toolchain\gcc-arm). So, select that folder as shown in Figure 8 (either typing the pathname or using the Browse button) and click on the  Finish button.

Figure 8: Project wizard - STEP 5

Our test project is almost complete. We only need to modify one thing to make it working on the Nucleo. However, before we complete the example, it is better to take a look at what has been generated by the GNU ARM plug-in.

Figure 9 shows what appears in the Eclipse IDE after the project has been generated. The  Project  Explorer  view shows the project structure. This is the content of the first-level folders (going from top to bottom):

Includes: this folder shows all folders that are part of the  GCC Include Folders ⁴.

src: this Eclipse folder contains the ^.c files that make up our application. One of these files is ^main.c, which contains the int main(int argc, char* argv[]) routine.

system: this Eclipse folder contains header and source files of many relevant libraries (like, among the other, the ST HAL and the CMSIS package). We will see them more in depth in the next chapter.

⁴Every C/C++ compiler needs to be aware of where to look for include files (files ending with  .h). These folders are called include folders  and their path must be specified to GCC using the -I parameter. However, as we will see later, Eclipse is able to do this for us automatically.

Hello, Nucleo! 52 include: this folder contains the header files of our main application.

ldscripts: this folder contains some relevant files that make our application work on the MCU. These are LD (the GNU Link eDitor) script files, and we will study them in depth in a subsequent chapter.

Figure 9: the project content after its generation

As said before, we need to modify one more thing to make the example project work on our Nucleo board. The GNU ARM plugin generates an example project that fits the Discovery hardware layout.

This means that the LED is routed to a different MCU I/O pin. We need to modify this.

How can we know to which pin the LED is connected? ST  provides schematics⁵ of the Nucleo board.

Schematics are made using the Altium Designer  CAD, a really expensive piece of software used in the professional world. However, luckily for us, ST provides a convenient PDF with schematics.

Looking at page 4, we can see that the LED is connected to the PA5 pin  ⁶, as shown in Figure 10.

⁵http://bit.ly/1FAVXSw

⁶Except for the Nucleo-F302RB, where LD2 is connected to PB13 port. More about this next.

Hello, Nucleo! 53

Figure 10: LD2 connection to PA5

PA5 is shorthand for PIN5 of GPIOA port, which is the standard way to indicate a GPIO in the STM32 world.

We can now proceed to modify the source code. Open the  Include/BlinkLed.h and go to line 19.

Here we find the macro definition for the GPIO associated to the LED. We need to change the code in the following way:

Filename: include/BlinkLed.h

19 #define BLINK_PORT_NUMBER (0)

20 #define BLINK_PIN_NUMBER (5)

BLINK_PORT_NUMBER defines the GPIO port (in our case GPIOA=0), and BLINK_PIN_NUMBER the pin number.

Nucleo-F302R8 is the only Nucleo board that has a different hardware configuration regarding the LED LD2, because it is connected to pin PB13, as you can see in schematics. This means that the right pin configuration is:

1 #defineBLINK_PORT_NUMBER (1) 2 #defineBLINK_PIN_NUMBER (13)

Ok. We can proceed compiling the project. Go to menu  Project->Build Project. After a while, we should see something similar to this in the output console[ˆch3-flash-image-size].

Hello, Nucleo! 54

Invoking: Cross ARM GNU Create Flash Image

 arm-none-eabi-objcopy -O ihex "hello-nucleo.elf" "hello-nucleo.hex"

Finished building: hello-nucleo.hex

Invoking: Cross ARM GNU Print Size

 arm-none-eabi-size --format=berkeley "hello-nucleo.elf"

text data bss dec hex filename

5697 176 416 6289 1891 hello-nucleo.elf

Finished building: hello-nucleo.siz  09:52:01 Build Finished (took 6s.704ms)