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FreeRTOS+TCP and FreeRTOS+FAT Examples
Running on an Atmel SAM4E ARM Cortex-M4 microcontroller

[Buildable TCP/IP and FAT FS Examples]


RTOS and TCP/IP running on SAM4E Xplained Pro Don't have any hardware? You can still try the RTOS TCP and FAT examples now by using the Win32 demo, which builds with free tools, and runs in a Windows environment.

The Atmel SAM4E ARM Cortex-M4 TCP/IP and FAT demo includes the following standard examples:

FreeRTOS+FAT is used to mount a FAT formatted SD card. The mounted file system then provide the storage for both the HTTP and FTP server examples.

The project builds using the free Atmel Studio GCC based development tools, and targets the Atmel SAM4E Xplained Pro evaluation kit.


Hardware Setup

No specific hardware setup is required.

Locating the Project

The Atmel Studio project that builds the demo described on this page is located in the /FreeRTOS-Plus/Demo/FreeRTOS_Plus_TCP_and_FAT_ATSAM4E directory of the FreeRTOS Labs download.

Software Setup #1: Setting a Static or Dynamic IP Address

Allocating an IP address to the RTOS TCP/IP target
Network address settings in FreeRTOSConfig.h
The FreeRTOSIPConfig.h and FreeRTOSConfig.h header files are the FreeRTOS+TCP and FreeRTOS configuration files respectively. Both can be opened from within the Atmel Studio IDE.

If a DHCP server is used on the network to which the SAM4E is connected, then set ipconfigUSE_DHCP to 1 in FreeRTOSIPConfig.h, and no further IP related network address configuration is necessary. If a hostname is configured then it is not necessary to know the IP address assigned to the SAM4E by the DHCP server because the SAM4E can be addressed directly by its hostname. The IP address can however be viewed, as it is printed out using the UDP logging facility.

If there is no DHCP server connected to the network then set ipconfigUSE_DHCP to 0 in FreeRTOSIPConfig.h, and instead configure the IP address and netmask manually using the configIP_ADDR0/3 and configNET_MASK0/3 constants in FreeRTOSConfig.h. Note the IP address constants are in FreeRTOSConfig.h, rather than FreeRTOSIPConfig.h, because they are related to the application, and not the TCP/IP stack directly.

It is necessary to ensure a manually configured IP address is compatible with the netmask. In most cases a compatible IP address will be one that uses the same first three octets as the host computer. For example, if the IP address of the host computer is, then any 172.25.218.nnn address, other than when nnn is 0, 255, or already present on the network, is compatible.

It is also necessary to set a gateway address that is correct for the network to which the SAM4E is being connected, or at least compatible with the netmask if no gateway exists. This step is necessary to prevent an internal sanity check triggering a configASSERT() failure. The gateway address is set using the configGATEWAY_ADDR0/3 constants in FreeRTOSConfig.h.

Software Setup #2: Setting the MAC Address

The MAC address is set using the configMAC_ADDR0/5 constants in FreeRTOSConfig.h.

If only one target that is running a FreeRTOS+TCP example is connected to the network then it will not be necessary to modify the MAC address.

If multiple targets that are running FreeRTOS+TCP examples are connected to the same network then it will be necessary to ensure each target has a unique MAC address.

Software Setup #3: Setting the Hostname

It is often more convenient to identify a node on the network using a text name, rather than an IP address. This is especially the case when the IP address is assigned by DHCP, and it therefore not known. For example, rather than sending a ping request to an IP address, such as "ping", a ping request can instead be sent to a hostname, such as "ping MyHostName" (where "MyHostName" is the name assigned to the network node).

If only one target that is running a FreeRTOS+TCP example is connected to the network then it will not be necessary to modify the default hostname, which is set to "RTOSDemo". If multiple targets that are running FreeRTOS+TCP examples are connected to the same network then it will be necessary to assign a different hostname to each target.

The hostname is set by the mainHOST_NAME constant at the top of the main.c source file. Depending on the network topology, it may also be possible to use a second hostname set by the mainDEVICE_NICK_NAME constant, which is also defined at the top of main.c.

Software Setup #4: Setting the Echo Server Address

If the TCP echo client example is used then set the constants configECHO_SERVER_ADDR0 to configECHO_SERVER_ADDR3 in FreeRTOSConfig.h to the IP address of a suitable echo server. FreeRTOS+TCP will then send echo requests to, and receive echo replies from, the configured echo server.

Software Setup #5: Print and Logging Messages

Directing RTOS TCP/IP stack debug output
Logging configuration in FreeRTOSConfig.h
In FreeRTOSIPConfig.h, FreeRTOS_debug_printf() is disabled, and FreeRTOS_printf() is set to send TCP/IP stack and application logging messages over UDP. The IP address and port number to which the UDP logging messages are sent, along with a few other logging related parameters, are set using constants within FreeRTOSConfig.h, which are shown in the image on the right.

Log messages are buffered for transmission by a low priority background RTOS task.

Log output can be viewed in many different terminal programs, including UDPTerm, from Cinetix.

Software Setup #6: Hardware Specific Settings

The project is delivered pre-configured to execute on a SAM4E Xplained Pro evaluation board. It may be necessary to update the IO configure to use the demo on different hardware, or update the network driver if a different PHY is used.

Running Examples

The instructions below describe how to build, download then execute the application on a SAM4E Xplained Pro evaluation board:
  1. Follow the software configuration steps detailed above.

  2. If available, insert a clean FAT formatted SD card into the SAM4E Xplained Pro's SD card socket.

  3. Inspect the comments at the top of main.c, and set the constants that build individual examples into and out of the demo.

    Note: If an SD card is not being used then do not include the HTTP or FTP server examples.

  4. Ensure the SAM4E Xpalained Pro hardware is connected to the host computer (the computer running Atmel Studio) using the target's debug USB port, and a suitable network using an Ethernet cable.

  5. First press F7 to build the project, and then press F5 to program the target flash memory, and start the application executing

LED0 will toggle every half second when the application is executing.

Basic Connectivity Test

It is advised to test basic connectivity before experimenting with the examples linked below. This can be done by pinging the target. If ping replies are received, then the application is both running and connected to the network correctly.

To ping the device, open a command prompt and type "ping ", where is the name assigned to the target - which by default will be "RTOSDemo".

If a ping reply is not received then turn DHCP off, assign the target a static IP address, and try again using the assigned IP address in place of the host name.

Instructions describing how to set a static IP address, and how to set a hostname, are provided in the setup instructions on this page.

pinging the TCP target
Pinging the target, and receiving ping responses

Included Examples

The project includes the following examples:

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