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GPIO example using Eclipse

 

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Overview

In this section, you will build and run a sample application to access GPIO using the M4 core. We will use buttons as inputs and LEDs as outputs.

In this module, you will:

  • Install the GNU MCU Eclipse plugin via the Eclipse Marketplace
  • Configure Eclipse for cross-compilation
  • Build your first Eclipse project for the Cortex-M4

Materials required

  • Serial-to-USB converter

Step 1

GNU MCU Eclipse (formerly known as GNU ARM Eclipse) is an Eclipse CDT plug-in that includes extensions and tools for embedded Arm and RISC-V development. It allows you to create and manage projects, including building and debugging for those targets.

The easiest way to install GNU MCU Eclipse is via the Eclipse Marketplace. Open the Marketplace by clicking on Help -> Eclipse Marketplace....


  • Eclipse Marketplace menu item

    Eclipse Marketplace menu item

On the Marketplace window, search for GNU MCU Eclipse and click Install. Accept the license terms and proceed. You will be asked to restart Eclipse.


  • Eclipse Marketplace search and install

    Eclipse Marketplace search and install


  • Plugin installation confirm

    Plugin installation confirm


  • Plugin license prompt

    Plugin license prompt


  • Plugin install anyway

    Plugin install anyway


  • Eclipse plugin restart

    Eclipse plugin restart

Step 2

Since you've already installed the GNU Arm Embedded Toolchain in the previous section, it should be automatically be detected by the GNU MCU Eclipse plugin.

Let's set up and build your first Eclipse project for the M4 core. We will use the GPIO example application that's bundled with FreeRTOS.

Create a new Eclipse project by clicking File -> New -> Project...


  • Eclipse new project

    Eclipse new project

Then select C/C++ -> C Project


  • Eclipse New C Project

    Eclipse New C Project

Give your project a name. On "Project type", select Empty Project. On "Toolchains", select "ARM Cross GCC". Click Next.


  • Eclipse toolchain selection

    Eclipse toolchain selection

Click next again to create the default Debug and Release configurations.


  • Eclipse debug release

    Eclipse debug release

Check if "Toolchain path" is already filled with the path you've installed the toolchain to in the previous section. Click Finish.


  • Eclipse confirm toolchain path

    Eclipse confirm toolchain path

Step 3

Using your preferred file manager or the command line, go to your project directory. It's located inside the Eclipse workspace directory which you've set up when Eclipse first starts.

Once inside your project directory, create a subdirectory called sources.

$ cd <your_project_diretory>
$ mkdir sources
$ cd sources

Now you're going to copy some files from the FreeRTOS repository used in the previous tutorial.

From the FreeRTOS directory, copy the platform folder to your sources directory.

$ cp -r ~/freertos-toradex/platform ./

Note: In this demo, we will build a bare metal application. If you're going to use FreeRTOS in your application, make sure to also copy the rtos folder from the FreeRTOS directory to your sources directory.

From examples/imx7_colibri_m4, copy the files board.c, board.h, clock_freq.c, clock_freq.h, gpio_pins.c, gpio_pins.h, pin_mux.c and pin_mux.h to a folder examples/imx7_colibri_m4 inside your sources directory.

$ mkdir examples
$ cd examples
$ mkdir imx7_colibri_m4
$ cd ../..
$ cp examples/imx7_colibri_m4/{board*,clock_freq*,gpio_pins*,pin_mux*} examples/imx7_colibri_m4

Step 4

It's necessary to make a small change to the gpio_pins.c file. On line 34, comment out the define for gpio_ctrl.h:

gpio_ctrl.h
@@ -31,7 +31,7 @@ #include <assert.h> #include "gpio_pins.h" #include "board.h" +//#include "gpio_ctrl.h" -#include "gpio_ctrl.h" #include "gpio_imx.h" gpio_config_t gpioLed = {

then save the file.

From examples/imx7_colibri_m4/driver_examples/gpio_imx, copy hardware_init.c and main.c to your sources directory.

$ cp examples/imx7_colibri_m4/driver_examples/gpio_imx/{main.c,hardware_init.c} ./

Your project directory should look like this:


  • Eclipse file tree

    Eclipse file tree

Step 5

To configure the toolchain, right-click your project on Project Explorer, then go to Properties.


  • Eclipse Project Properties Menu

    Eclipse Project Properties Menu

Step 6

On the Properties window, go to C/C++ Build -> Settings. In the Tool Settings tab on the right panel, the Target Processor section should look like this:


  • Eclipse Target Processor Toolchain Settings

    Eclipse Target Processor Toolchain Settings

Step 7

In the Optimization section:


  • Eclipse project Optimization settings

    Eclipse project Optimization settings

Step 8

In the compiler Preprocessor section, define three symbols:

CPU_MCIMX7D_M4
ARM_MATH_CM4
__DEBUG

  • Eclipse project preprocessor settings

    Eclipse project preprocessor settings

Step 9

Specify the include paths so the compiler can find the header files:


  • Eclipse project compiler includes

    Eclipse project compiler includes

Step 10

In the linker General section, we'll set the application to use the i.MX 7's tightly coupled memory (TCM) region to store the data:

"MCIMX7D_M4_tcm.ld"

  • Eclipse project linker general settings

    Eclipse project linker general settings

Step 11

Also, we must set the path to the linker file in Linker -> Libraries:

"${ProjDirPath}/sources/platform/devices/MCIMX7D/linker/gcc"

  • Eclipse linker libraries settings

    Eclipse linker libraries settings

Step 12

In the linker Miscellaneous settings, check "Use newlib-nano" and "Do not use syscalls":


  • Eclipse linker misc settings

    Eclipse linker misc settings

Step 13

In GNU ARM Cross Create Flash Image -> General settings, set Output File Format to Raw binary:


  • Eclipse create flash image settings

    Eclipse create flash image settings

Step 14

In the Toolchains tab, make sure Create flash image is selected:


  • Eclipse toolchains create flash image check

    Eclipse toolchains create flash image check

Click Apply and Close.

Step 15

Click the Build icon or press Ctrl+B to build the project.

The console should show "Build Finished" and there should be a new Binaries item in Project Explorer.

You will find the compiled binary in the Debug subdirectory inside your project directory.

Step 16

Copy the .elf file to an SD card and upload the firmware to the M4 core just like on the previous tutorial:

$ cp <your_project_directory>/Debug/gpio_demo.elf /media/toradex/SDCARD

Power up your board, stop the boot process to enter the U-Boot console, then enter:

Colibri iMX7 # fatload mmc 0:1 ${loadaddr} gpio_demo.elf
...
Colibri iMX7 # bootaux ${loadaddr}
...
## Starting auxiliary core at 0x1FFF8311 ...
Colibri iMX7 # 

FAQ

Can I use TFTP instead of an SD card to upload the firmware