MTK 446 electronic timer: firmware upgrades

The MTK 446 electronic timer is based round an industrial micro controller. This is a general purpose device that uses a firmware program to enable it to act as a timer. The firmware contains the instructions that enable the timer to accept and store setup and flight programs from your PDA and then to use the information in them to control your model during a flight.

From time to time the MTK 446 firmware may be upgraded as MTK enhance the timer's operation or fix bugs. This section describes what you'll need and the steps you must take to carry out an upgrade.

Requirements

Upgrading the firmware requires the following items:

• your PDA with the correct setup and flight programs for the timer(s) you're about to upgrade. Don't continue with the upgrade until you're sure you know which of these go with each model and timer.
• a PC with a second serial port, COM2
• An adapter cable or D-9 female gender changer. This is used to connect the timer's standard programming cable to COM2 on the PC. If you don't have this already, MTK can supply this with your first timer.
• the MTK programming jumper. MTK should supply this with your first timer.
• LOAD_IN.EXE, an MTK supplied DOS command-line program to load the replacement firmware into the timer.
• The replacement firmware module. This is a single file with a .HEX extension, e.g. MTK447N.HEX
• A DOS batch file to control the loading process, e.g. DOWNLOAD 447N.BAT

The last three software items are distributed by e-mail and can be used immediately they have been received. They should all be saved into the same folder on your hard disk. Its name and location are not important.

Upgrading a timer

This process looks daunting as written out but its actually easier to do than to describe. Perform the following steps in order:

1. Check that you can get at the programming jumper socket on the timer. This depends on how the timer is installed in your model: you may need to take the timer out to get at it.
2. Disconnect the servo from the timer but leave the tow hook connected.
3. Connect the programming cable to the COM2 port of your IBM PC. Use the adapter cable or gender changer to make this connection.
4. Plug the programming jumper into the timer.
5. Connect the battery.
6. Start the DOS batch file, which is called something like DOWNLOAD 447N.BAT, by double clicking it in Windows Explorer or typing its name at the command prompt. It will display a summary of the steps you've just completed and pause.
7. Double check that all is ready and tap the RETURN key. The loader will run and should report that the timer is inaccessible. The batch file will pause again after displaying reminders for the next two steps.
8. Start the timer as usual by using the tow hook. The LED will light and the timer will buzz continuously.
9. Plug the programming cable into the timer.
10. Tap the RETURN key to start the download. The loader program will report details of what it is about to do and then display several lines of dots to show download progress. During the download the timer will make the usual 'downloading in progress' noise. When the download is complete the message 'download OK' should be displayed to show that it finished successfully. This will be followed with a short reminder about the rest of the process. At this point you'll see the DOS prompt again or, if you ran the download by double clicking from Windows Explorer, the DOS window will report that it is inactive. It can now be closed unless you're following the final on-screen prompts.
11. Disconnect the programming cable from the timer.
12. Disconnect the battery.
13. Remove the programming jumper.
14. Reconnect the battery.
15. Start the timer with the tow hook back. The timer should be in WAITING mode and making the usual double beep. The timer is now running the upgraded firmware but has lost the servo and altimeter calibrations as well as the last flight program. These must now be reloaded.
16. Connect the programming cable between your PDA and the timer.
17. Reload the setup program from your PDA followed by the flight program.
18. Disconnect the programming cable from the timer.
19. Reconnect the servo. Note that the black wire must be outermost!
20. Check that the flight program is working as expected.
21. Go and fly

Repeat these steps for each timer you're upgrading.