The latest firmware 100_085 and software for PS-310U version 1 can be found here:
For PS-310U V1 (E1868 chip) you can even use the latest software version 19.0109.0066 (it works as well although not mentioned with the E1868 chip) on the website:
Elite Silicon is the manufacturer of the used E1868 chip.
For the PS-310U V2 which uses the E2868 chip use the firmware from the Elite Silicon Website under firmware section and the above mentioned software version 19.0109.0066.
Changed to latest software version released on 2019/02/19.