David Smart / SWUpdate Featured

Software Update via Ethernet - the mbed application can pull down an updated application binary from a web server and activate that binary. This library works only with the LPC1768, as it relies on the magic-chip boot-loader mechanism.

Dependents:   WattEye X10Svr PUB_SWUpdate

Success!! With this library, a network connection, and a web server hosting a new binary image, you can update the mbed firmware over the air (FOTA) - well, at least via Ethernet so far.

As of March 2015, it has been tested with the following mbed official libraries:

And a custom derivation:

  • HTTPClient v33, v32, which includes a custom HTTPFile.

Part of the update process involves checking the integrity of the downloaded binary file, for both a checksum and the program (file) size. To create this additional information, a small perl script is used (the important part is only 20 lines of code). See the documentation in the header file.

After the new binary is successfully downloaded, the checksum and the size are evaluated and if correct, then the old binary file is removed (this is the only way to cause the new binary to activate).

The mbed can then be automatically reset to activate the new image, or this may be deferred in case there is some other process necessary for an orderly restart.

Details are in the SWUpdate header file, and PUB_SWUpdate is a publicly accessible demonstration program for this library.

Diff: SWUpdate.h

Revision:
3:c69fff55fc60
Parent:
2:ef2ac9627546
Child:
4:1a3656ae80dc
--- a/SWUpdate.h	Sat Jun 14 16:15:30 2014 +0000
+++ b/SWUpdate.h	Sat Jun 14 18:18:28 2014 +0000
@@ -15,10 +15,46 @@
 /// will try to download it. If that succeeds, then it can
 /// optionally reboot to activate the new software.
 ///
-/// @todo check the freshly downloaded sw integrity. Since we have
-///     to remove the old .bin file before the new one will execute,
-///     it is in the device' best interest to ensure that new one
-///     is a good one.
+/// The files on the web server are as follows:
+///   @li myprog.bin - The actual binary file. The name is unimportant, but
+///             this is the binary file that was generated from the sources.
+///   @li myprog.txt - A corresponding text file. The root name must match
+///             that of the binary file.
+///
+/// The myprog.txt file shall have 3 comma-separated numbers in it.
+///   version,checksum,filesize (ex: "21,41384,107996")
+///
+///   @li version is a simple number. If the number is different than
+///             what is stored on the local file system, then the program
+///             will be updated (even if the server number is lower).
+///   @li checksum is the decimal representation of a simple 16-bit checksum.
+///   @li filesize is the decimal representation of the size of the file.
+///
+/// You can create the server "myprog.txt" file with this perl script (not
+/// every detail is shown, but it should be easy to figure out).
+///
+/// # Read current .txt file
+/// <<code>>
+/// open (FT, "<$txt") || die("Can't read $txt.");
+/// $ver = <FT>; chomp $ver; close FT;
+/// $ver =~ s/(\d+),.*/$1/;
+/// print "Current Version is {$ver}\n";
+/// 
+/// # Read new .bin file
+/// open (FB, "<$bin") || die("Can't read $bin.");
+/// binmode FB;
+/// while (sysread(FB, $c, 1))
+///     {
+///     $cksum = ($cksum + ord($c)) & 0xFFFF;
+///     $byteCount++;
+///     }
+/// close FB;
+/// # Advance version
+/// $ver++; print "$ver Checksum is $cksum over $byteCount bytes.\n";
+/// open (FT, ">$txt") || die("Can't write update to $txt.");
+/// printf(FT "%d,%d,%d\n", $ver, $cksum,$byteCount);
+/// close FT;
+/// <</code>>
 ///
 /// @param url is a pointer to a text string of the url from which to download.
 /// @param name is the base filename of the binary file.