Connect USB HID with PIC18F4450 Code • Tech Projects

Universal Serial Bus (USB) provides a serial bus standard for connecting a wide variety of devices, including computers, cell phones, game consoles, PDA’s, etc.
USB Library contains HID routines that support HID class devices, and also the generic routines that can be used with vendor specified drivers.

USB HID Class

The HID class consists primarily of devices that are used by humans to control the operation of computer systems. Typical examples of HID class devices include :

Keyboards and pointing devices, for example: standard mouse devices, trackballs, and joysticks.
Front-panel controls, for example: knobs, switches, buttons, and sliders.
Controls that might be found on devices such as telephones, VCR remote controls, games or simulation devices, for example: data gloves, throttles, steering wheels, and rudder pedals.

Devices that may not require human interaction but provide data in a similar format to HID class devices, for example, bar-code readers, thermometers, or voltmeters. Connect USB HID

Many typical HID class devices include indicators, specialized displays, audio feedback, and force or tactile feedback. Therefore, the HID class definition includes support for various types of output directed to the end user.

Descriptor File

Each project based on the USB library should include a descriptor source file which contains vendor id and name, product id and name, report length, and other relevant information. To create a descriptor file, use the integrated USB HID terminal of mikroC PRO for PIC (Tools › USB HID Terminal). The default name for descriptor file is USBdsc.c, but you may rename it.

Important :

The USB library routines have been changed. Please, have this in mind when migrating projects from previous versions of the compiler.
Also, this relates to the descriptor source file, so it is necessary to create a new descriptor file in order to make your project work.

Library Routines

HID_Enable
HID_Read
HID_Write
HID_Disable
USB_Interrupt_Proc
USB_Polling_Proc
Gen_Enable
Gen_Read
Gen_Write

HID_Enable

Prototype	void HID_Enable(char readbuff, char* *writebuff);
Description	Enables USB HID communication.
Parameters	`readbuff:` Read Buffer. `writebuff:` Write Buffer. These parameters are used for HID communication.
Returns	Nothing.
Requires	Nothing.
Example	HID_Enable(&readbuff,&writebuff);
Notes	This function needs to be called before using other routines of USB HID Library.

HID_Read

Prototype	char HID_Read(void);
Description	Receives message from host and stores it in the Read Buffer.
Parameters	None.
Returns	If the data reading has failed, the function returns 0. Otherwise, it returns number of characters received from the host.
Requires	USB HID needs to be enabled before using this function.
Example	// retry until success while(!HID_Read()) ;
Notes	None.

HID_Write

Prototype	char HID_Write(char writebuff, char* len);
Description	Function sends data from Write Buffer `writebuff` to host.
Parameters	`writebuff:` Write Buffer, same parameter as used in initialization; `len:` specifies a length of the data to be transmitted.
Returns	If the data transmitting has failed, the function returns 0. Otherwise, it returns number of transmitted bytes.
Requires	USB HID needs to be enabled before using this function.
Example	// retry until success while(!HID_Write(&writebuff,64)) ;
Notes	Function call needs to be repeated as long as data is not successfuly sent.

HID_Disable

Prototype	void HID_Disable(void);
Description	Disables USB HID communication.
Parameters	None.
Returns	Nothing.
Requires	USB HID needs to be enabled before using this function.
Example	HID_Disable();
Notes	None.

USB_Interrupt_Proc

Prototype	void USB_Interrupt_Proc(void);
Description	This routine is used for servicing various USB bus events. Should be called inside USB interrupt routine.
Parameters	None.
Returns	Nothing.
Requires	Nothing.
Example	void interrupt() { USB_Interrupt_Proc(); }
Notes	Do not use this function with USB_Polling_Proc, only one should be used. To enable servicing through interrupt, `USB_INTERRUPT` constant should be set (it is set by default in descriptor file).