Suggestion needed about USB project

[abo_shreek11]

Hi
I have a simple project in which I type on a keyboard (USB one) and display the writing on 2X16 lcd. And for this, I chose the PIC18F4550 which has a usb module. I've read most of the examples which come with the CCS complier and most of them are about interfacing a device (keyboard, mouse, etc) to a PC through the PIC. I was wondering if the USB module can be used for my project in which no PC (which have the USB drivers) is used. And if so, a C example which reads a string from USB keyboard will be useful.



Thank You.

[Ttelmah]

No.
USB, is a 'master/slave' interface. Every bus, has one USB master device. The PIC, implements a USB _slave_ only.
A USB 'master', is complex. Code, several hundred times bigger, even for a very simple operation...
For your simple operation, several possiilities exit.
First, the keyboard, _may_ implement PS/2 as well as USB (most do). This is triggered, by holding one line of the connection to a level, when it is first switched on. The USB-PS/2 adapter units sold for keyboards do this. PS/2 master code, is readily available for the PIC.
Second, for a specific device, it _may_ be possible to implement a really crude subset of the USB communications, to talk to it. However think 'lot of work'.
Third, there are chips available with limited 'master' abilities. These are designed for the USB 'otg' specs, where things like cameras, can talk directly to printers. The commonest one, is the FTDI 'Vinculum', and a prototype version of this is available, that can talk to a PIC via RS232, or SPI, and implements a master that will talk to keyboards, and things like USB storage devices.

Best Wishes

[abo_shreek11]

Hi Ttelmah

Thanks for your rapid reply. What I got from you is that the USB module in the PIC is for slave_use_only in which a PC is needed. But I can use a USB-PS/2 adapter in which the keyboard can be USB and the adapter connect with the PIC through PS/2, isn't it ?

By the way, your answer is clear and I'll go for PS/2 keyboard.

Thank You.

[FvM]

I almost agree, except for the second part of this statement.

[Ttelmah]

Couple of comments.
No, the keyboard _won't_ be USB. The point is that most keyboards can switch between running in PS/2 mode, and USB mode. The adapters trigger this change. Most (except for a few really expensive ones), have nothing more in them, than a couple of connections, and you can implement these without the adapters. With the adapter attached, or the same connections made by you, the keyboard runs as a PS/2 device.
To Fvm, I make this point in my 'second' comment. Yes, limited USB operations to a single device, are not too bad, but like you, I think it'd be much easier to talk to the PS/2 interface instead.

Best Wishes