HD44780 has also option to use four bits data transfer mode which is very useful if we don’t have enough port bits in microcontroller to perform eight bit data transfer or if we would to save some port bits for other functions. LCD display’s control signal R/notW is permanently connected to the ground. LCD display has also signal R/notW which toggles between read/write mode of HD44780 chip. Eight bits are data bits (D7.D0), two bits serve as control signals E and RS. To communicate with LCD display ten bits are used. After receiving packet from endpoint 1 microcontroller’s firmware checks data consistency and immediately display it on LCD.

Microcontroller shares its USB RAM with Serial Interface Engine (SIE) which is directly connected to USB bus. Microcontroller has reserved in its RAM memory four banks as a USB RAM. After successful configuration of device we are able to send data via terminal to device. If you are familiar with USB you probably know that every USB device has to support bidirectional endpoint 0, because it is used during device’s enumeration process at first connection to USB Host. Endpoint 0 (EP0) and Endpoint 1 (EP1) both are bidirectional. So as you can see it’s the first limitation. LCD display allows displaying two lines with sixteen characters. LCD display (LCD → Liquid-Crystal Display) which was chosen to project is based on HITACHI HD44780 chip. Just choose the license type in the top right part. This software gives us possibility to send information to chosen USB device. mikroC PRO for FT90x has two licensing options available: the License Code and the USB. It is possible to download demo version of mentioned software.

HID terminal is a one of tools from toolsuite environment MikroC Pro. HID terminal is a software created by Mikroelektronika company.

After enumeration process of USB device, we switch on HID terminal. Main reason why I did it was that I wanted to prove to unfaithful people that my device really works online. I decided to add to USB device function which will allow it to display received data on LCD display. In previous project I have created USB 2.0 device which can communicate with computer via HID device class.

Mikroelektronika usb hid terminal