[G Tablet Q&A, Help & Troubleshooting] rajeevvp:
We'll have to take things step by step.

First, is the SD card on the camera a removable microSDHC card? If it is, you could just remove it and insert it into the gTablet's microSDHC slot instead of connecting the camera to a USB hub.

Second, have the 2 devices been detected correctly by the kernel? Both individually and then together on a USB-hub?

For example, if I connect my 1TB Maxtor USB HDD to the gTablet, the status bar message informs me that "SD card blank or has unsupported filesystem". This means that the drive was detected, but the NTFS filesystem on it was not recognized, and therefore the drive was not mounted (the vold program which does the mounting only likes ext4 or VFAT filesystems for automounting). I'm assuming that since you have a 500GB drive, it is formatted as NTFS?

If Android does not detect a drive insertion, check the kernel messages. In a Terminal, after I insert a USB drive, I do:

$ [B]dmesg | tail -n 20[/B]
[144874.547211] usb 1-1.1: New USB device found, idVendor=0d49, idProduct=7410
[144874.554415] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[144874.562368] usb 1-1.1: Product: Basics Desktop
[144874.567435] usb 1-1.1: Manufacturer: Maxtor
[144874.572010] usb 1-1.1: SerialNumber: 2HBEWHZR
[144874.580165] usb 1-1.1: configuration #1 chosen from 1 choice
[144874.589418] scsi0 : SCSI emulation for USB Mass Storage devices
[144874.601098] usb-storage: device found at 3
[144874.601123] usb-storage: waiting for device to settle before scanning
[144879.597766] scsi 0:0:0:0: Direct-Access Maxtor Basics Desktop 0125 PQ: 0 ANSI: 4
[144879.617283] sd 0:0:0:0: Attached scsi generic sg0 type 0
[144879.624170] sd 0:0:0:0: [sda] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)
[144879.634583] sd 0:0:0:0: [sda] Write Protect is off
[144879.639482] sd 0:0:0:0: [sda] Mode Sense: 2d 08 00 00
[144879.639505] sd 0:0:0:0: [sda] Assuming drive cache: write through
[144879.647662] sd 0:0:0:0: [sda] Assuming drive cache: write through
[144879.653918] sda: sda1
[144879.688927] sd 0:0:0:0: [sda] Assuming drive cache: write through
[144879.695477] sd 0:0:0:0: [sda] Attached SCSI disk
[144879.813410] usb-storage: device scan complete

to check if the drive was detected. I can see by the messages that the Maxtor drive was detected by the kernel and that I can mount it manually by using the /dev/block/sda1 device. If you don't see similar messages, you're out of luck. If the camera is also detected, it may show up as /dev/block/sdbn.

If everything is detected properly, but, just not mounted, you can mount things manually.

For this, you have to know which kernel you're running. There are 2 kernels that are commonly used on the gTablet: clemsyn's and pershoot's. I use pershoot's kernel so my instructions will be for that. The pershoot kernel supports NTFS filesystems, but, this support is not built into the kernel. Support is instead provided using kernel modules which you'll have to download first from the author's website and then load manually.

Download the correct kernel modules file for the running kernel. Find the kernel version first:

$ [B]uname -a[/B]
Linux localhost 2.6.32.40-cyanogenmod #1 SMP PREEMPT Fri May 13 17:37:53 EDT 2011 armv7l GNU/Linux

The kernel version is 2.6.32.40. I go to http://droidbasement.com/db-blog/ and download the kernel modules file for that kernel version which would be this file for Gingerbased ROMs: lib-2632.40_gb.tar.gz, or, this file for Froyo based ROMS: lib-2632.40.tar.gz. Note the "_gb" suffix. Extract the file on your PC and then transfer these 2 file onto the gTablet: nls_utf8.ko and ntfs.ko. You should, ideally, put them in /system/lib/modules, but, it you can just leave it on the gTablet's SD card.

Load the kernel modules (I'm assuming now that they're on /mnt/sdcard), then mount the HDD:

$ [B]su[/B]
# [B]insmod /mnt/sdcard/nls_utf8.ko[/B]
# [B]insmod /mnt/sdcard/ntfs.ko[/B]
# [B]mount -t ntfs -o nls=utf8 /dev/block/sda1 /mnt/usbdisk[/B]

The HDD's contents will now be present in /mnt/usbdisk which is a directory that already exists for mounting USB devices. The /dev/block/sda1 device name we determined using the kernel messages. If you have partitions on the HDD, you can mount them individually using their device names which look like /dev/block/sdan, where n is a number. Look in /dev/block/ to see what partitions can be mounted.

To mount the camera, create a new directory somewhere else, let's say /mnt/sdcard/tmp, and then mount it in that directory. I'm assuming here that the camera's SD card was detected as /dev/block/sdb1 and that it has a VFAT (aka FAT32) filesystem on it.

$ [B]su[/B]
# [B]mount -t vfat /dev/block/sdb1 /mnt/sdcard/tmp[/B]

After you've finished, unmount both devices before you unplug:

$ [B]su[/B]
# [B]umount /mnt/usbdisk[/B]
# [B]umount /mnt/sdcard/tmp[/B]