Updating the firmware on a Sharp BD-HP20U Blu-ray player using a USB stick and a Mac was not entirely straightforward for me. The process is a bit brittle, so I’m documenting it in the hopes that I (and others) won’t waste so much time dealing with it next time around.
Sharp distributes the firmware update as a ZIP archive. After you download and unpack it you will have a file with a .RVP extension, e.g., HP20U118.RVP. This file needs to be placed on the USB stick which will then be attached to the Blu-ray player, but the player will be finicky about the condition of the USB device.
The filesystem on the USB stick must be FAT16 – the player will not read FAT32. DiskUtility.app only seems able to do FAT32, so I had to drop into the shell and use /sbin/newfs_msdos to format the device. Plug the stick into your Mac and launch Terminal.app. From the terminal make sure the USB stick is unmounted (replace /dev/diskX with the actual device file of the USB stick):
$ diskutil umountdisk /dev/diskX
Next, format the USB stick with a FAT16 filesystem (again, replace /dev/diskX as appropriate):
$ newfs_msdos -F 16 -v FIRMWARE /dev/diskX
The -F 16 option specifies the FAT16 filesystem, and -v FIRMWARE assigns the label “FIRMWARE” to the new filesystem. You can use any 1-11 character string that adheres to DOS file-naming rules instead of “FIRMWARE”. Whatever you use will end up being all uppercase regardless of how you enter it. See the newfs_msdos man page for more information.
Now remount the USB stick:
$ diskutil mount /dev/diskX
This will mount the USB stick on /Volumes/FIRMWARE (the mount point is derived from the volume label).
Now copy the .RVP file onto the USB stick (replace /path/to/HP20U118.RVP with the actual path to whatever firmware version you downloaded):
$ cp /path/to/HP20U118.RVP /Volumes/FIRMWARE
Quickly ensure that there are no other files on the USB stick other than the .RVP file you just copied over:
$ ls -a /Volumes/FIRMWARE
Besides the firmware update, there may be several hidden files. They must be removed before the device can used by the Blu-ray player. If there are any, any other files on the disk besides the firmware update itself, the Blu-ray player will refuse to run the update complaining there are other files on the disk.
$ rm -rvf /Volumes/FIRMWARE/.[a-zA-Z0-9_]*
This command will verbosely remove any hidden files. If for any reason there are any regular files (files whose names do not begin with a dot) besides the firmware update, they should be remove as well.
Finally, unmount the USB device:
$ diskutil umountDisk /dev/diskX
When this completes the USB device can be safely unplugged from your Mac. Plug it into your Blu-ray player and follow the operating manual instructions for applying firmware updates. At the time of this writing the operating manual for the HP-BD20U is available here.