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Connect USB HID with PIC18F4450 Code

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.

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Tags: #connect#hid#pic18f4450#usb
Ibrar Ayyub By Ibrar Ayyub
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At a glance

CategoryCommunication & Interfacing
IncludesCode
Reading time~5 min
Jump to a section
  1. USB HID Class
  2. Library Routines
  3. HID_Enable
  4. HID_Read
  5. HID_Write
  6. HID_Disable
  7. USB_Interrupt_Proc
  8. USB_Polling_Proc
  9. Quick Solutions to Questions related to USB HID Project:
  10. Related projects

Summary of Connect USB HID with PIC18F4450 Code

USB HID Library enables communication between PIC microcontrollers and host computers using Human Interface Devices like keyboards, mice, and sensors. It includes routines for enabling, reading, writing, and disabling USB connections via interrupt or polling methods. A descriptor file is essential for defining device identity and report structures.

Parts used in the USB HID Project:

  • USB Library with HID routines
  • Descriptor source file (USBdsc.c)
  • mikroC PRO for PIC integrated USB HID terminal
  • HID_Enable function
  • HID_Read function
  • HID_Write function
  • HID_Disable function
  • USB_Interrupt_Proc routine
  • USB_Polling_Proc routine

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 with PIC18F4450 Code

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.

Note  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
Code listing
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
Code listing (2)
// 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
Code listing (3)
// 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
Code listing (4)
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
Code listing (5)
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).

Connect USB HID with PIC18F4450 Code schematichUSB_Polling_Proc

Prototype void USB_Polling_Proc(void);
Description This routine is used for servicing various USB bus events. It should be periodically, preferably every 100 microseconds.
Parameters None.
Returns Nothing.
Requires Nothing.
Example
Code listing (6)
while(1) {
  USB_Polling_Proc();
  kk = HID_Read();
  if (kk != 0) {
    for(cnt=0; cnt < 64; cnt++)
      writebuff[cnt]=readbuff[cnt];
  HID_Write(&writebuff,64);
  }
}

 

 

For more detail: Connect USB HID with PIC18F4450 Code

  • What devices are supported by the HID class?
    The HID class supports keyboards, pointing devices, front-panel controls, game controllers, bar-code readers, thermometers, and voltmeters.
  • How do I create a descriptor file for my project?
    Use the integrated USB HID terminal of mikroC PRO for PIC under Tools to generate the file.
  • Can I rename the default descriptor file?
    Yes, the default name is USBdsc.c but you may rename it as needed.
  • Does the USB library require re-creation of descriptor files when migrating?
    Yes, USB library routines have changed so a new descriptor file must be created for older projects.
  • Which function must be called before using other USB HID routines?
    You must call HID_Enable before using any other functions in the library.
  • What is the difference between USB_Interrupt_Proc and USB_Polling_Proc?
    USB_Interrupt_Proc handles events inside an interrupt routine while USB_Polling_Proc should be called periodically every 100 microseconds.
  • Can I use both interrupt and polling procedures simultaneously?
    No, you must use only one of them; do not use both together.
  • How does the HID_Read function indicate failure?
    If data reading fails, the function returns 0; otherwise it returns the number of characters received.
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Ibrar Ayyub

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough...