Deploying Your First Application

This chapter describes how to write a "hello world" application on the Pico-G1 board, build it into the rootfs, flash it, and run it — completing the full flow from writing source code to running it on the board.

Step-by-Step Operations

1. Create a New Project

For a clean and maintainable project structure, place the application under SDK/source/app:

mkdir -p source/app/helloworld  # Create the helloworld application
cd source/app/helloworld/        # Change directory
touch helloworld.c               # Create the .c file
touch Makefile                  # Create the Makefile

2. Write the Application

vim helloworld.c

helloworld.c is as follows:

#include <stdio.h>

int main(void)
{
    printf("hello world from firmware!\n");
    return 0;
}

3. Write the Makefile

vim Makefile

The Makefile is as follows:

# SDK root directory.
# This Makefile is located under source/app/helloworld/.
# Going up three levels returns to the SDK root.
SDK_DIR := $(shell cd $(shell pwd)/../../.. && /bin/pwd)

# Include the common SDK build configuration.
# This defines the cross-compiler, compile flags, link flags, rootfs output directory, and other variables.
include $(SDK_DIR)/build/base.mk

# Final executable file name.
TARGET := helloworld

# Source file list.
SRCS := helloworld.c

# Derive the object file name from the source file name.
# For example, helloworld.c -> helloworld.o
OBJS := $(SRCS:.c=.o)

# Declare phony targets to avoid conflicts with same-named files.
.PHONY: all clean install

# Default target.
# Running make first builds the final program.
all: $(TARGET)

# Link rule.
# Links the .o object files into the final executable.
$(TARGET): $(OBJS)
	$(CC) $(SDK_LD_CFLAGS) -o $@ $^

# Compile rule.
# Compiles a .c source file into a .o object file.
%.o: %.c
	$(CC) $(SDK_USR_CFLAGS) -c -o $@ $<

# Install into rootfs.
# The final on-board path will be /usr/bin/helloworld
install: all
	@mkdir -p $(XMEDIA_ROOTFS_DIR)/usr/bin
	@cp -f $(TARGET) $(XMEDIA_ROOTFS_DIR)/usr/bin/$(TARGET)
	@chmod 755 $(XMEDIA_ROOTFS_DIR)/usr/bin/$(TARGET)
	@echo "Installed $(TARGET) to $(XMEDIA_ROOTFS_DIR)/usr/bin/$(TARGET)"

# Clean build artifacts.
clean:
	rm -f $(TARGET) $(OBJS)

4. Build

Build the application

# Run from the SDK root directory:
make -C source/app/helloworld clean   # Clean the previous build results
make -C source/app/helloworld         # Re-cross-compile to generate the board-runnable helloworld

Build rootfs

# Run from the SDK root directory:
make rootfs_clean
make rootfs

Install the application into the rootfs directory

# Run from the SDK root directory:
make -C source/app/helloworld install

Expected output:

ljh@lcwt-KNPP-D32-R-Series:~/GK7206$ make -C source/app/helloworld install
make: Entering directory '/home/diskh/ljh/GK7206/source/app/helloworld'
Installed helloworld to /home/diskh/ljh/GK7206/out/xm7206v12a/rootfs/usr/bin/helloworld
make: Leaving directory '/home/diskh/ljh/GK7206/source/app/helloworld'

 #### make "-C source/app/helloworld install" completed successfully! ####

At this point, switching to the /out/xm7206v12a/rootfs/usr/bin directory shows the helloworld application.

ls -l out/xm7206v12a/rootfs/usr/bin/helloworld

5. Package

make fs_image

6. Flash

See Flashing chapter: Image Flashing to flash the SPI image.

7. Run the Application

Use SSH or serial port to enter the board's shell (command-line) environment.

cd /usr/bin/
helloworld

The following is printed:

hello world from firmware!