It allows to quickly and effectively communicate with the desktop computer. Using HID means that this oscilloscope does not require drivers (only the oscilloscope software).
This is a project that Iíve been planning on putting together for a long time. After creating an oscilloscope using a PIC12F675, I wanted to create a simple and effective USB oscilloscope using the higher performance PIC18F2550. During the development of this project, I learned quite a bit about USB HID communication.
The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is used in this project. The component marked ĎRESí is a 20MHz resonator.