As we saw in the previous chapter, sensors and actuators are connected to an embedded device using some pins or interface like GPIO (General Purpose I/O), I2C, SPI and so on. If we have a closed device that doesn’t expose this kind of interfaces, we have to use standard communication port, like serial (RS232 with DB9 connector) or USB. In the latter case, there is Phidgets (http://www.phidgets.com/) that provides products for USB sensing and control. There are a lot of sensors (distance, gas, light, temperature, motion, proximity, touch, …), motors and other devices (RFID, relays, LCD displays, …) that can be connected to our PC or embedded device based on Compact O.S. via USB with all available drivers to use them.
Phidgets supports Windows OS and on the web site is available a page (http://www.phidgets.com/docs/OS_-_Windows) where you can download the drivers for the PC. In this way, you have a Phidget Control Panel that you can use to test your sensors using a friendly UI. In the installation package are included native drivers and .Net based wrapper assemblies to use Phidgets device inside your .Net applications.
The drivers and .Net assemblies are also available for Windows CE (5.0 or newer) based systems (http://www.phidgets.com/docs/OS_-_Windows_CE), for all type of architectures (ARM4VI, x86 and MIPSII). In this case, you can use a CAB file to install native drivers and .Net Compact Framework assembly on your platform or you can build an OS image that already contains them.
Figure 7.1 : Phidgets web site
For the example in this chapter, we use the InterfaceKit 8/8/8 and the precision light sensor to implement a simple system to monitoring lightness in a room.