I'm going to buy a PIC32 which has inbuilt USB support. What is the difference between "FS Device", "FS Device/Host/OTG", and "HS Device/Host/OTG"? Am I right in thinking that the "OTG" aka "on the go" means that the USB can be plugged in and out at anytime?
Electrical – the difference between “FS Device”, “FS Device/Host/OTG”, and “HS Device/Host/OTG”
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The USB can either be in device mode or in OTG mode. You cannot have OTG on the same USB bus as a host like a computer.
Multiple OTG devices can switch between host & device mode using "HNP" (Host negotiation protocol) but you can't do that with a pure host.
You would need two separate USB busses - one between the PC and the PIC, and one between the PIC and the devices. I don't think there is any PIC device that has 2 distinct USB interfaces.
I would suggest using a second device along side the PIC32 to act as a USB device to connect to the PC, and use the PIC32's USB in OTG mode to talk to the devices. This other device could be as simple as a FTDI chip to talk to the PIC32 through RS232, or something more powerful like another PIC (maybe a PIC18 with USB support) so you can talk through other protocols like I²C or SPI.
There is a development kit microchip that performs with all the technical features that you require, it is USB Starter Kit II
In the picture I have marked the 3 USB ports (1 debug only) and the jumper to select the power source
The kit is very good documented, the datasheet contains all the schematics and there are numerous "Application Notes" on how to realize both the hardware this software. It can be used as the basis, for your study.
If you did not find any interesting application with its own code of microcontroller, can try to search in other families as PIC24F and PIC24H will notice that with a few changes in the layer configuration of hardware will be able to reuse the code without any problems.
In addition I can tell you that there are many more open hardware projects, based on PIC32, with careful research on the Internet will be able easily locate other schematics and application notes.
Best Answer
Any USB cable can be plugged in or out at any time. Part of the design. Has nothing to do with OTG (see below).
FS stands for "full-speed", 12 Mb/s (USB 1.0/1.1).
HS stands for "high-speed", 480 Mb/s (USB 2.0).
There is another higher speed in use, "Super-speed", which is 5 Gb/s (USB 3.0). Higher speeds still (e.g. 10 Gb/s) have been announced, but I'm not sure there are any products using them.
The Host is the electronics that is controlling the conversation between it and the slave device. A typical Host is a PC or laptop.
A Device is the electronics that is being controlled by the host. A typical Device would be a PC keyboard or mouse, USB flash drive, disk drive, smartphone, or a DVD player.
OTG as you guessed is "on-the-go". But it means the electronics can act as either a host or a device. An example is a smartphone, which can act as a Device when connected to a laptop, but a Host to other devices.