Nuts and Volts - February 2012

check the Experimenter pushbutton. If it is depressed and the USB is ready to transmit, the pot value is transmitted over USB (using API putsUSBUART()) and is also displayed on the Experimenter LCD. We also make use of the stdio.h C library to help with data formatting and the analog library to digitize the pot value at the AN4 pin.

Rotary Encoder Knob USB Service Demo

This demo uses the Mini-Kit rotary encoder as the data source to the Experimenter. Rotary encoder data is captured as a string containing direction CCW (-) or CW (+) and accumulative encoder rotation counts to the PC. The data string originating on the Experimenter will be displayed on both the Experimenter LCD, as well as the PC terminal. No additional software files are included in the demo workspace. Rotary encoder device drivers are integrated into the Main function as an interrupt service. The workspace is included in the rotary demo folder. Open EXPROTARY.mcs, then build and download to the Experimenter. The ProcessIO() is as follows: In this example, we first look for a rotary count difference before proceeding. If there is a difference, we format the string, display and output it, and update the new rotary count internally.

In Conclusion

We’ve embarked on long journey in order to understand how to create a virtual serial port to a PC using the Experimenter, its USB interface, and Microchip’s USB firmware stack. A number of demos were covered, with an introduction to a new analog library for the Experimenter ADC. We can now maintain required legacy communications to a PC using this new bag of tricks, and with the five steps covered, we now have a valuable tool set that creates a serial port with minimal hardware and software impact to any future Experimenter designs. Until next time, happy 32-bit processing! NV

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