1.  Introduction

The etrex Mountain Bike Flavor is an unofficial modification of the graphical symbols and screens inside the etrex firmware, that create a MTB oriented etrex GPS. This means that rather than the general-purpose symbol set that includes airborne, marine, hiking and urban symbols, you’ll have a set of symbols more oriented towards bikers. Some of the graphic screens are also changed to reflect the fact that you’re willing to ride rocks on a metal contraption.

 Before you continue, make sure you are aware of this: THIS IS AN UNOFFICIAL FIRMWARE. Though I checked it, uploading it is at your own risk.

That out of the way, I can say that for me this worked nicely. 

2.  What’s in it for Mountain Bikers

The set of Waypoint symbols is radically changed. 18 of the 29 symbols are modified, mostly those related to marine and airborne. They’re replaced by new symbols to reflect things mountain bikers may find useful, as shown in the table at left.

In addition, there’re many graphics changes in the screens to reflect the fact that this GPS is used by a mountain bike dude. I’m confident you’ll discover them as you operate the GPS.

If you feel this is right for you, at this point, check your firmware version:

• Turn the etrex on, and flip to the Menu page

• Choose Setup  and then choose System

• Check the software version shown on screen. Warning: Garmin added a 'feature' to firmware 2.14 that prevents loading any previous firmware. In fact, there's nothing else in the 2.14 firmware that makes it worth loading. Absolutely no new features.  So if you've got firmware 2.11, my suggestion is to stay with it, and not move to 2.14, as this move is a one way trip.

  For software version 2.14 (latest version), download the 2.14 package
  For software version 2.11, download the 2.11 package

  Use the updater.exe program to upload the bike version firmware to the GPS, as explained below

3.  How to create the etrex Mountain Biker’s Flavor

• Make sure the GPS has fresh batteries or is connected to a power supply so that it won't die in the middle of the firmware upload.
• Unzip the package by running it in a directory of your choice.
• Go to the BikeUploader directory and run Updater.exe. Choose com port, and upload the modified firmware.
• If you’re curious how I’ve created these new symbols, read on. Otherwise, that’s it.

One last thing: there’s a set of windows bitmaps in the BMP directory of the symbols. These can be used in Oziexplore by copying these BMPs to a directory called SYMBOLS under oziexplore directory. Once in Oziexplore, you can choose to place these symbols on a map using the Map Events.

4.  Advanced Topics

Read this if you’re interested how these symbols were created or want to modify them to create different or more symbols or create a new flavor. You need to be extra careful before uploading a new untested firmware to the etrex. You may render it inoperable, in which case you will need to reload the original firmware or may have some firmware malfunction.

4.1.              What’s in the package

• RAW, PSD, GIF – these directories hold the changed symbols in RAW, Photoshop and GIF format
• Newicons.exe – this program patches firmware.bin with RAW files described to it by the file whowhere.dat.
• Hackbmap.exe – this program is a utility that displays a binary file, such as the firmware files with selectable row/byte, color scheme and offset. It was written specifically for etrex firmware hacking.
• Firmware 2.11/2.14 RAW file Offset.xls – an excel file that describes all the bitmaps (that I was able to hunt) in version 2.11/2.14 of the etrex firmware.
• Symbols.xls – Summary of the old and new symbols in the Mountain Bike release.

4.2.              Modifying bitmaps

Use photoshop or another .psd enabled tool to open the appropriate bitmap in the PSD directory. Make sure that:

• You backup the original symbol to a different name
• You use Indexed Color – check this under Image-Mode
• You DO NOT modify the size of the image. This is really important.
• You keep the original image orientation.

 Once done, save the resulting file and a .RAW format of the symbol in the RAW directory. Make sure that:

• You saved it under the same name as the original picture.
• You checked all of the above once more.

 For extra checks, see the next section on hackbmap.

4.3.              Hunting bitmaps in an existing release

The bitmaps in the etrex firmware are inline with the code, thusly there’s no easy way to find them. However, many of them are lumped close to each other. Since they are not just black and white (some use 2 bits for grayscale), and since there are different color schemes for different bitmaps (01 may represent gray or inversegray or inverse or true), it’s even harder.

 However, there is a tool,hackbmap, which greatly helps in this endeavor. It needs to see the EGAVGA.BGI file as well.

Note: Because these programs are old DOS programs, this needs to be done in a directory with a path to it. I did this in c:\

To use it, simply run it with the firmware file as a parameter, for example, hackbmap 013001000214.rgn

hackbmap displays the firmware and by setting the offsets (using b command) and bytes per row (w command) and color scheme (r command), you can scan the firmware and find the graphics by examining the patterns. To find the offset, move the bitmap exactly to the top left corner and read the offset. The offsets I found are documented in the Excel file Firmware 2.11/2.14 raw bitmap offsets.xls” Check the numbers shown there with hackbmap. Type h for all options. If you saw the movie ‘Matrix’ you may feel a bit like ‘cipher’ after a while.

 Hackbmap is also indispensable for comparing firmware, and making sure a new firmware is indeed correct and the new bitmaps are at the right offsets and at the right size. A bit more on this later.

4.4.              Creating new bitmaps

There’s lot’s of experimentation here, and plenty of risk in making your GPS inoperable if you’re not careful, but its fun. The basic idea is to hunt down the bitmaps, and create new ones that are exactly the same size as the one you want to replace. This is done by noting the size of the bitmaps and their aspect ratio and orientation and creating one with the same parameters. Hackbmap is great for this.

Once the new bitmap is created, an entry must be made in the file whowhere.dat.

This file is used by newicons.exe to patch the existing firmware. The entry is self explanatory, but you’ll have to experiment with hackbmap and the color schemes to see that the bitmaps are fine and especially not bigger than the original ones.

To patch the firmware, rename the .rgn file to an old DOS file 8.3 format, like firmware.bin, and run the newicons on it. For example:
newicons firmware.bin

Note: Because these programs are old DOS programs, this needs to be done in a directory with a path to it. I did this in c:\

I found it useful to run two concurrent sessions of DOS with hackbmap in each one and toggle between the two to see any differences. I set the DOS session property to reflect the name of the firmware in the title bar, and set it to max size so that I could alt-tab between the two, visually making the comparison. Note that you can’t actually do anything in this mode, you’ll have to switch to full screen dos, or Windows will do it for you.

5.  Credits

This flavor is based on the hacketrex created for hikers by Datrex, which posted the results on his web page. We’ve exchanged emails and I’d like to thank him for his clarifications.