Technical Tips


USB thermometer DS18B20 temperature sensor. Included Visual Basic 6 software, Visual Studio 2005 C# code, PIC C code and a circuit diagram. The PIC interface to the PC is HID class.
The DS18B20 sensor has a range of -55 to 125 centigrade in accuracy of 0.5 degree and resolution of 9 to 12 bits. The interface to the pic is via one digital line, the 1 and 0 is determined by pulse duration. The code includes the commands to read temperature and set the resolution.
HID class (human interface device) is a class of devices like the mouse and the keyboard, the data transfer rate is limited to 64KB/S. The PC already has a driver for HID USB.
C# code is modified Microchip code from the USB framework, Microchip Solutions v2012-04-03.
VB6 code includes guidance to setting up the PC. The PC register the PID (Product ID) and VID (Vendor ID) of the USB device when it's plugged, the VB code uses these ID's to communicate with the device. For commercial VID it is needed to buy it from USB-IF, but in your lab you can use any number.
The source code is derived from freeware from these sources: ,
You are free to use the circuit diagram and the VB software with no limitations.

The C# and the VB6 applications are a combined digital and graphic thermometer.

Circuit Description
See also Technical Tips

Pin 14 is 3.3V internal supply for the USB transceiver.
Pins 15,16 are the data lines to the USB connector on the PC.
Pin 20 is the PC 5V powering the PIC. It is limited to 100mA by the PC. 0.47uF is for decoupling.
For USB wiring info:

Any type of case can be used.