Electronic – Pressure/Force sensor

You would be better off with a barcode reader with serial or PS/2 interface. Sometimes it is as easy as swapping the cable for a different one to change the interface type, depends on your barcode scanner model.

If you really want to use the USB barcode reader, you need either

• a PIC that can be an USB host like PIC24FJ256GB106 or PIC32MX420FxxxH or
• a standalone USB host controller like MAX3421E
• a software implemented USB host stack - I know they exist for Atmel, not sure about PIC

Even with these hardware solutions it would still take some effort to implement enumeration, the HID device class and so on.

Outside the scope of your question and probably more expensive than a serial or PS/2 barcode scanner, but there is a precompiled firmware for FTDI's Vinculum chips that bridges an USB HID device to a microcontroller's SPI interface, see USB HID to SPI Master Sample Application ROM.

You arn't going to find any generic device that does everything you want, with an unknown amount of different sensors or modules. The dedicated alarm system devices have custom computer interfaces, and have hardware designed to account for power needs and protection from shorts or esd, considerations for the sensors it is designed for, etc.

What you want to do will require multiple parts. The first is the computer interface. That is easy. You can go the diy route and go for an arduino or launchpad or similar microcontroller board with usb to serial adaptors. You will need to program the microcontroller for your final system. There is dedicated hardware you can use though. What you are looking for would be "USB GPIO Boards" (GPIO = General Purpose Input/Output) with how ever many channels you need. A quick google can show you some, like a 32 channel one for 45 bucks.

The other other option is a gpio port expander. If you are going with a raspberry pi, you can skip the arduino and it's programming, and just go directly with making a linux program for which ever port expander you decide on. With an i2c port expander, you can put multiples on the same raspberry pins, making it as expandable as you need. These can even interrupt so your computer doesn't need to constantly check to see if there has been a change in a sensor. And since it's linux, most port expanders already have drivers for them.

-- The second part is the actual interfacing to the sensors. It will depend on the individual sensors you go with. You will need to power them over the entire length, will need to protect the port expander from over current (transistors or optocouplers) and it's a bit hard to even guess at without knowing what you will be using.