There is some firmware available:
https://www.rigol.eu/Public/Uploads/uploadfile/files/20230321/20230321002306_6418886a99c29.zipIts a rar archive, extract using:
unrar x 20230321002306_6418886a99c29.zip
then there's a GEL file, extract using:
tar xvf DP900_DP2000_Update.GEL
-rw-r--r-- adil/root 35836928 2023-02-08 13:52 tina-r40-m2ultra.swu
-rw-r--r-- adil/root 105900 2022-04-08 04:44 sousa_fpga.024.bin
-rw-r--r-- adil/root 185 2023-02-08 13:52 image_info.txt
-rw-r--r-- adil/root 108 2023-02-08 13:52 checksum.txt
then there's a cpio archive:
cpio -i <tina-r40-m2ultra.swu
-rw-r--r-- 1 henk henk 3656 Apr 12 22:04 sw-description
-rw-r--r-- 1 henk henk 256 Apr 12 22:04 sw-description.sig
-rw-r--r-- 1 henk henk 15728640 Apr 12 22:04 recovery
-rw-r--r-- 1 henk henk 1196032 Apr 12 22:04 uboot
-rw-r--r-- 1 henk henk 32768 Apr 12 22:04 boot0
-rw-r--r-- 1 henk henk 4194304 Apr 12 22:04 kernel
-rw-r--r-- 1 henk henk 14680064 Apr 12 22:04 rootfs
Then there's a squashfs filesystem:
file rootfs
rootfs: Squashfs filesystem, little endian, version 4.0, xz compressed, 14674551 bytes, 1446 inodes, blocksize: 262144 bytes, created: Wed Feb 8 12:49:37 2023
So we have a sunix linux system running on your PSU unit together with an FPGA.