It is done. I could finish the hack. Let me sum up the single steps, which worked for me:
My device was delivered with firmware 2.02
1.
Install "Ultra Sigma"-Software from Rigol homepage
2.
Note your serial number (press the "Utility" key and touch "System Info")
3.
Prepare an USB-Stick (FAT32) with the downgrade file. You can find the link here:
https://www.eevblog.com/forum/testgear/new-rigol-16-bit-function-generators-dg800900-series/msg3157600/#msg3157600Copy only the GEL-file, not the complete ZIP-file !
Switch off your DG and insert the USB-stick.
Switch on the DG and press the "Help" key continously. The bootloader should now print a message if you want to program the firmware on the stick.
(In my case only this installation was possible. Plug in the stick during operation didn't work. The update was recognised but not processed)
4.
Prepare the magic USB-stick (> 1GB). This was the most difficult part. I tried it out with Windows 10 and HXD and it didn't work. Even writing the bytes with Linux didn't work. In the end I tried out to format the stick with Linux and write then the bytes. This worked !
You can find the binary file which contains the byte sequence to be programmed in the attachment (DG800_sardinha.zip). Unzip it to place which you can access to from your booted Linux. This could be another USB-Stick
Start a Linux installation, format the USB-stick and write the byte sequence.
I prepared an USB-Stick with Rufus
https://rufus.ie/en_IE.htmland used a small linux ISO:
http://blog.puppylinux.com/fossapup64-release(I had to disable the security boot in BIOS to be able to boot from the stick)
Format the USB-stick
(check out that you choose the correct device !!! In my case it was sda1)The Linux command is:
sudo mkfs.vfat /dev/sda1
Mount the drive on which you have copied the file with the byte sequence (DG800_sardinha.bin). I used an additional USB-stick which was device sda2.
The linux command to write the bytes was in my case:
sudo dd if=/mnt/sda2/DG800_sardinha.bin of=/dev/sda1 bs=512 seek=2000000
5.
Switch on your DG (without the magic stick). After booting plug in the stick. A message box pops up with the text "Wait". The box is visible for ca. 6s. The time was much longer with my other sticks which failed.
Start "Ultra Sigma" and connect the USB-cable with your PC. The DG should now be recognised and now you can send the SCPI command to reprogram your serial number you have noted in step 2
(Only press the SEND-button):
:PROJ:SN DGxxxxxxxxxxx
You can check if this worked with the command:
*IDN?
The result should now be your original serial number.
I also sent the command to write the model (again only SEND-button)
:PROJ:MODE DG992
This command failed and after that there were no further commands accepted. The DG is after the downgrade to v1.08 already a DG992 so I am not sure if this command is really necessary
6.
Restart your DG again and check out if the serial number and model are correct
7.
Prepare an USB stick with GEL-File which is in the attached file "Finish_Upgrade_2.04.zip"
Plug in the stick. A "Wait"-message box pops up and after that the update-fie is recognised you need to confirm the update with "OK"
8.
Prepare an USB stick with update 2.04. Here is the link:
https://int.rigol.com/Public/Uploads/uploadfile/files/ftp/DG/%E8%BD%AF%E5%9B%BA%E4%BB%B6/SardineII(ARM)Update-v00.02.04.00.00.rarPlug in the stick. A "Wait"-message box pops up and after that the update-file is recognised you need to confirm the update with "OK"
9.
Check out the firmware version in your DG whether everything is OK
Thanks to tv84, Vtech and all others for this hack !
Now we are all looking forward to calibrating the DG up to 100MHz