Build and run μClinux

Figure 2 shows the μClinux build procedure. Start the console on LinuxPC and execute the following steps in the directory where uClinux-dist is expanded.

Figure 2 μClinux build procedure

Run make menuconfig

Here you can set the device vendor, CPU architecture, kernel, device driver, etc. to be used. Here, set as follows.

・”Vendor” ⇒ “Altera”

・”target” ⇒ “Nios2nommu”

・“kernel Version” ⇒ “linux-2.6.x”

・“Libc Version” ⇒ “None”

Finally, check "Default all settings (lose changes)" and save the changes. Automatically generate a “.Config” file.

If you want to change the kernel and userland settings, check "Customize Kernel Settings" and "Customize Vendor/User Settings" after completing the first build.

Run make vendor_hwselect

Here, the PTF file output from SOPC_builder is used to automatically set the CPU and memory to be used and generate the address map. Here, set as follows.

・“--- Please select which CPU yor wish to build the kernel against:” ⇒ “altera_nios2”

・“--- Please select a device to upload the kernel to:” ⇒ “ext_flash”

・“--- Please select a device to execute kernel from:” ⇒ “ddr_sdram_0”

Run make, make linux image

Build the μClinux kernel and root file system with the “make” command. and then generate an executable binary file (zImage) with the “make linux image” command. If there are no errors, a “zImage” file will be created. Download this file to your target board.

Download and run kernel

Launch the Nios II EDS “Command Shell” and execute “nios2-download” to download the “zImage” file to DDR_SDRAM on the target board. Then execute "nios2-terminal" to start μClinux console (JTAG_UART). Figure 3 shows the image up to execution.

Figure 3 μClinux execution image

If a boot message and prompt are displayed on the console, µClinux boot is complete. Figure 4 shows the startup screen.

Figure 4 Start μClinux

In addition to commands that can be used in Linux, network applications such as ``telnet'', ``ftp'', and ``httpd'' are also prepared to some extent, so we recommend you to try them once. Figure 5 shows the screen when connecting to the target Web server with a browser from the host PC.

Figure 5 Connection from host browser to web server

kernel debugging

If you only use the functions provided by uClinux-dist, you do not need to debug the kernel, but if you develop device drivers or port to a custom board, you will need to debug the kernel as well. . I myself have created device drivers for the LCD included in the development kit and the external RTC, but debugging using the old printk statement is not efficient.

Nios II does not have “KGDB” as a kernel debugging method on Linux, so instead, we will introduce a kernel debugging method using “nios2-gdb-server” introduced last time.

Figure 6 shows the kernel debug environment.

Figure 6 Kernel debug environment

Start the command shell of Nios II EDS, execute "nios2-gdb-server", and make the target board wait for connection. Start the Insight Debugger with the ``nios2-elf-insight'' command and open the ``linux'' file generated in the ``uClinux-dist/linux-2.6.x'' directory. Start the “Target Selection” screen from “File ⇒ Target Setting” and set as follows.

・target: “Remote/TCP”

・Hostname: “localhost”

・Port: <Port number specified in nios2-gdb-server>

Click the Run button to download the kernel binary and stop at the beginning of the kernel. After that, source-level debugging becomes possible in the same way as a general debugger.

Figure 7 Kernel debug screen