I bought the Longruner (no, not a typo!) 7″ touch screen and it turned up after a few days. It’s nicely made and similar to this, though it looks slightly different. That hand must be a dolls hand!
It doesn’t have any documentation but there was a DVD with three MS Word documents which I opened on my Windows PC (It comes in useful sometimes!). One of them the “7inch HDMI Display user Manual(En).docx” has a photo of the three ports.
There’s a full size HDMI socket and a USB to Android (Micro USB-B I believe) cable is included that plugs into a USB port and either of the Android type ports. You can either have power and touch screen with the port nearest the HDMI as I did or just power alone, if you want to use it as a monitor. The two green squares show the USB and touch/power cables.
When I switched it on, it just sat there saying no HDMI signal. That MS Word document included instructions to edit the config.txt in \boot. Of course I had no display but the Pi was plugged into the network and I ran WinSCP which logged in and let me view files. I don’t think you can edit files as root with WinSCP, and that config.txt file needs root access to edit it.
However I am a long time user of Putty. (You can also get putty from putty.org but I don’t know if that is also an official one). After that I could ssh into the pi, do a sudo -s command to switch in root and then nano /boot/config.txt to edit config.txt.
Here’s a photo of my fat finger moving the cursor round the screen. It works surprisingly well, and the display is lovely though my photos probably do not do it justice.
These are the lines you paste into the end of the config.txt, save it out and reboot.
max_usb_curren=1 hdmi_force_hotplug=1 config_hdmi_boost=7 hdmi_group=2 hdmi_mode=87 hdmi_drive=1 display_rotate=0 hdmi_cvt 1024 600 60 6 0 0 0
Now I just have to figure out how to use it in my games. The display is 1024 x 600 btw.
Plugging in a second monitor worked fine as this photo shows. The blacks are darker on the touchscreen but that’s just because the gammas don’t match and I was too lazy to change them!