Thread: Convert fenix 5S/5/5X Plus to D2 Delta S/Delta/Delta PX

If I understand correctly I should be able to flash a Fenix 5X Plus to a D2 PX by downloading the current D2 PX firmware (e.g. D2DeltaPX_610.gcd) and flashing it via Garmin's web updater. Years have past, is there reason to believe Garmin has changed anything in the Fenix 5 firmware that prevents flashing D2 firmware?

The first post suggests conversion to rgn is required. When I use the rgnTool to write a rgn, the tool complains boot.bin should be in section 1...hope you know what you are doing. Should I assume this message can be ignored?

For reference I own an older D2 without PO2 sensor and it would be useful to get a backup watch, as well as obtain the capability to measure PO2 at altitude.

Thank you.

Not sure I understand what you are asking about the PO2 sensor. If you don't have the sensor on your watch, you can't flash it to have that.
I did the flashing a couple of years ago and it's worked great. Not a problem. I was wondering the same if there would be anything that they might have changed. My understanding (not an expert at this), you just flash whatever firmware you want. You can flash an old one and the watch will update to the latest one. In other words, Garmin doesn't know if you did the flashing or not.

Originally Posted by Serhito

Thank you so much !! Any way to donate for your work ?

I'm happy if you're happy. No donation necessary.

Originally Posted by vscvsc

If I understand correctly I should be able to flash a Fenix 5X Plus to a D2 PX by downloading the current D2 PX firmware (e.g. D2DeltaPX_610.gcd) and flashing it via Garmin's web updater. Years have past, is there reason to believe Garmin has changed anything in the Fenix 5 firmware that prevents flashing D2 firmware?

That's not quite right. Garmin firmwares check whether the firmware was meant for that device by verifying the hw_id (device/model number) and some flags in the firmware files. If they don't match, the firmware isn't installed - even if the hardware is exactly the same. That's why I've modified the firmware files on the MEGA share so e.g. the hw_id and flags of the D2 Delta firmware match those of the Fenix 5 Plus.

Originally Posted by vscvsc

The first post suggests conversion to rgn is required. When I use the rgnTool to write a rgn, the tool complains boot.bin should be in section 1...hope you know what you are doing. Should I assume this message can be ignored?

Please don't use that method anymore. It worked for converting a Fenix 5 Plus to a D2 Delta, but was a one-way thing as e.g. the D2 Delta bootloader doesn't have the Preboot mode needed to force-flash the RGN. The method using the modified firmware update files is much safer and works in both directions.

And as Serhito pointed out already, you can't add hardware features this way. If there's no SpO2 sensor (i.e. a red led) on your watch, a firmware change can't add it. Also, flashing e.g. the D2 Delta firmware onto a D2 Charlie won't work either as those have different hardware specs and you'll most probably end up with an expensive paperweight.

Originally Posted by vscvsc

Thus I'm concerned what Garmin is shipping now still permits flashing over the Fenix code.

AFAIK those watches are cross-flashable regardless of their firmware version. There are downgrade firmwares to downgrade to an older version from which you can cross-flash a Fenix Plus to a D2 Delta.

Originally Posted by vscvsc

But now that I'm looking at the MEGA files you created modified firmware for the Fenix 5 plus, not the 5X plus.

All Fenix 5 Plus variants and - as you already found out - all D2 Delta variants have the same firmware. The Fenix 5 Plus firmware runs under hw_id 0x0b54 (fenix 5S Plus) and the D2 Delta range has hw_id 0x0c7c (D2 Delta S). So the files in the MEGA folder work for all variants.

Originally Posted by vscvsc

I found your Python code. I believe I'm using it correctly and I'm able to change the HW_ID for the current D2 delta firmware to the Fenix (e.g. 3111 or 0xc27). That said what flags need to be changed? Also is the first second the boot loader, where you are using the Fenix boot loader with the "payload" from the D2, when building the flashable D2 file?

In case of the watches, there are the fields 1014 and 1015. Those have to match for the watch to accept the firmware file. First binary in the GCD file is the bootloader, the second one the actual firmware. You must always flash both (which means modifying the flags twice in the .rcp file) when cross-grading as a firmware upgrade has 2 stages:

1. The main OS verifies whether the firmware file matches the current running one (hw_id, 1014, 1015, newer version) and if it does, copies the GCD to some staging area.
2. The watch reboots and the bootloader now does the same verification again. If it doesn't match, the update is discarded.

Now imagine what happens if the main OS is a D2 Delta but the bootloader is from the Fenix. Any update or cross-grade would never be installed as either the system wouldn't copy the firmware to the staging area (Fenix firmware rejected by D2 OS) or the bootloader wouldn't accept the file (D2 firmware rejected by Fenix bootloader). There's one user from early on who has a watch in this state and we never managed to fix it. Also Preboot mode doesn't work for him for some reason.

n.b.: Beta firmwares usually only have the main OS inside. So don't try to create a cross-grade version from those.

@mbirth
Can you please upload the file to convert a fenix 5S plus to D2 Delta S?
Or should I use the 5 plus file?
TIA