USB Interface using PIC


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  1. #1
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    Default USB Interface using PIC

    Has anyone used a PIC to develop a USB Interface. From what i have read the 16C745 which has a USB interface onboard is not flashable. Is there another alternative, preferably easily obtainable in the UK.

    I would, at this stage, like to use a Windows GUI (Via VB) to switch outputs on the PIC to HIGH and LOW as selected.

    Can anyone help in this quest.

    Many thanks,

    Steve

  2. #2
    OXIMBIT's Avatar
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    The PIC18F4550 has a USB2 interface, it's brilliant!! I can use it behave like a Mouse or use the USB interface as virtual serial port. There are other devices in the USB family as well.
    Last edited by OXIMBIT; - 13th March 2005 at 19:23.

  3. #3


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    Do you have any example of code, that this pic is show as a virtual com in windows?

  4. #4
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    Heres some code, It should all convert to Pbpro really easly

    Code:
     
    '
    ' General purpose USB CDC test program.
    '
    ' Transmits data from several different buffers.
    ' And displays the contents of the USBIN buffer on the LCD
    '
    ' Uses transmit and receive detection using the CARRY flag (STATUS.0)
    '
    ' Communicate via the serial terminal set to the com port that the USB connects too.
    '
    	OPTIMISER_LEVEL = 2								' Enable the optimiser at level 2
    	Device = 18F4550								' Choose a device with on-board full speed USB
        XTAL = 48										' Set the oscillator speed to 48MHz (using a 20MHz crystal)
        
        REMINDERS = OFF									' Disable all reminders
        
        LCD_DTPIN = PORTD.4								' LCD data port attached to PORTD
    	LCD_RSPIN = PORTE.0								' LCD RS pin attached to PORTE.0
    	LCD_ENPIN = PORTE.1								' LCD EN pin attached to PORTE.1
    	LCD_INTERFACE = 4								' 4-bit Interface
    	LCD_LINES = 2									' 2 line LCD
    	LCD_TYPE = ALPHANUMERIC							' Use an Hitachi alphanumeric LCD								
            
        USB_DESCRIPTOR = "CDCDESC.INC"					' Point to the CDC DESCRIPTOR file (located in the INC\USB_18 folder)
        
        Dim PP0 As Byte SYSTEM							' USBPOLL status return
        Dim VAR1 As Word								' General purpose variable
        Dim ARRAY1[20] As Byte 							' Used to hold some output characters
       	Dim OUT_BUFFER As String * 20					' Used to hold some output characters
        Dim IN_BUFFER As String * 20					' Used to hold some input characters
        
        Symbol CARRY_FLAG = STATUS.0					' High if microcontroller does not have control over the DP buffer
        Symbol TRNIF = UIR.3							' Low if USB Busy
    '------------------------------------------------------------------------
    ' The main program loop starts here 
       
        DelayMS 200											' Wait for things to stabilise
        ALL_DIGITAL = True									' Set PORTA and PORTD to digital mode
        Clear												' Clear all RAM before we start 
        Cls													' Clear the LCD
        
        Repeat												' \
        	USBPoll											'   Wait for the USB interface to become attached
        Until PP0 = %00000110								' /
        
        StrN ARRAY1 = " ARRAY BUFFER\n\r"    				' Fill the array with NULL terminated characters
        OUT_BUFFER = " STRING BUFFER\n\r"                   ' Fill the string with NULL terminated characters
        
    	VAR1 = 0     										' Reset the counting variable
    	While 1 = 1											' Create an infinite loop
            Repeat											' Wait for USB input
            	USBIn 3, IN_BUFFER, Auto					' Poll the USB and Receive some data from endpoint 3
            Until CARRY_FLAG = 0							' Keep looking until data is able to be received
            
            Print At 1,1,"USB BUFFER"  						
            Print At 2,1,IN_BUFFER                     		' Display the contents of the USB buffer on line 2 of the LCD
            Clear IN_BUFFER                            		' Then clear the buffer for the next time
                   
            __USBOUT_BUFFER = " USB BUFFER\n\r" 			' Place characters directly into the USB TX buffer string
    '
    ' Transmit from the USB's internal TX buffer String. NULL terminated.   
            Repeat  
    			USBOut 3, __USBOUT_BUFFER, Auto 			' Poll the USB and Transmit the buffer from endpoint 3 
        	Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
    ' Transmit from a NULL terminated array         
            Repeat  
    			USBOut 3, ARRAY1, Auto 						' Poll the USB and Transmit the buffer from endpoint 3 
        	Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
    ' Transmit from a NULL terminated String         
            Repeat 
    			USBOut 3, OUT_BUFFER, Auto 					' Poll the USB and Transmit the buffer from endpoint 3 
        	Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
    ' Transmit from a NULL terminated code memory String         
            Repeat  
    			USBOut 3, TEXT_STRING, Auto 				' Poll the USB and Transmit the buffer from endpoint 3 
        	Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
    ' Transmit a NULL terminated quoted string of characters        
            Repeat  
    			USBOut 3, " QUOTED STRING\n\r", Auto 		' Poll the USB and Transmit the buffer from endpoint 3 
        	Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
    ' Transmit 12 characters from a code memory String         
            Repeat
            	USBOut 3, TEXT_STRING, 12 					' Poll the USB and Transmit only 12 characters of the buffer from endpoint 3
            Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
            
            __USBOUT_BUFFER = "\n\rVAR1 = " + Str$(Dec,VAR1) + "\n\r"  ' Convert VAR1 into a string
    ' Transmit from the USB's internal TX buffer String. NULL terminated. 
    		Repeat
    			USBOut 3, __USBOUT_BUFFER, Auto  			' Poll the USB and Transmit the buffer from endpoint 3 
            Until CARRY_FLAG = 0							' Keep trying if the microcontroller does not have control over the buffer
            Repeat : Until TRNIF = 1						' Wait for completion before transmitting anything else
            Inc VAR1 
        Wend												' Go wait for the next buffer input
    	
        
    TEXT_STRING: CData " CODE MEMORY BUFFER\n\r",0

  5. #5


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    oke thanx for the info i give it a try only i'm suppriced about how windows will detect this device

  6. #6
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    Having now got my USB PICs for development (all of the 18F USB Series), are there any examples of how to switch the outputs of the PIC HIGH or LOW as driven by the PC.

    I'm looking at an application where by the front end is developed using VB, but then the control is by the PIC. So VB sends a command to the PIC to make a desired PORT HIGH or LOW.

    It seems fairly simple in its concept, but i can't find any examples of this on the WEB / Forums.

    Any help / pointers would be appriciated.

    Thanks.

    Steve.

  7. #7
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    Aren't there any examples included with the compiler?

  8. #8
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    Not as far as im aware, but i may be wrong. They just seem to be about complex data transfer opposed to simple switching commands.

    Of course if you are aware of any, then please correct me if i'm wrong.

    I'm using PicBasic Pro.

    Many thanks,

    Steve

  9. #9
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    The Compiler I'm using has many demos including one to Implement the functionality of a Jan Axelson demo which flashes Leds at the Pic end in response to inputs made at the PC. And I just remembered one where as I move my mouse pointer of a picture of a Prototype board the Led's light up on the real board.

    I can only suggest you contact Melabs for more help.
    Last edited by OXIMBIT; - 25th April 2005 at 19:33.

  10. #10
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    Sounds like what exactly after. Two questions then, what Compiler are you using and can you send these demos to me on email? I've sent you a PM with my email address.

    Many thanks,

    Steve

  11. #11
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    Steve I have sent you a PM with some example code.

    Tim

  12. #12


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    DOes any of you have a schematic of how to connect the PIC18F2455 to the usb?

  13. #13


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    And does somebody have a example prog that is realy for pbp FOR A pic18f2455

  14. #14
    OXIMBIT's Avatar
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    Have you tried looking in the manual?

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    Yes i tried i try to compile the example code:

    USBCDC but can't get it work, i want to use a PIC2455.

    This is the PBP code:

    ' USB sample program for PIC18F4550 CDC serial port emulation

    ' Compilation of this program requires that specific support files be
    ' available in the source directory. You may also need to modify the
    ' file USBDESC.ASM so that the proper descriptor files are included. For
    ' detailed information, see the file PBP\USB18\USB.TXT.

    buffer Var Byte[16]
    cnt Var Byte

    LED Var PORTB.0


    Define OSC 48


    USBInit
    Low LED ' LED off

    ' Wait for USB input
    idleloop:
    USBService ' Must service USB regularly
    cnt = 16 ' Specify input buffer size
    USBIn 3, buffer, cnt, idleloop

    ' Message received
    Toggle LED

    buffer[0] = "H"
    buffer[1] = "e"
    buffer[2] = "l"
    buffer[3] = "l"
    buffer[4] = "o"
    buffer[5] = " "
    buffer[6] = "W"
    buffer[7] = "o"
    buffer[8] = "r"
    buffer[9] = "l"
    buffer[10] = "d"
    buffer[11] = 13
    buffer[12] = 10
    buffer[13] = 0

    outloop:
    USBService ' Must service USB regularly
    USBOut 3, buffer, 14, outloop

    Goto idleloop ' Wait for next buffer

  16. #16


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    Getting further, the PBP goes compiling now only thany he asked for the MPASM compiler so i installed this compiler made the path settings.

    Then he start the MPASM only it gives the error.

    Error in parameter "18F4550"

  17. #17


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    Another step closer,

    Windows detect a USB device but an unknown, and installing the "PBPCDC"
    drivers have no effect. sombody?

  18. #18


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    Windows detects the USB PIC now,

    only now i need a working description.asm file. Because the standard description (demo pbp files) don't set every setting in windows.

    Like manufacture, product and more.

  19. #19
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    Quote Originally Posted by Tissy
    Having now got my USB PICs for development (all of the 18F USB Series), are there any examples of how to switch the outputs of the PIC HIGH or LOW as driven by the PC.
    look at this
    http://www.alecmcnamara.freeserve.co.uk/piccalc/
    you find HIDcomm component from Microchip for really easy VB development

  20. #20
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    Default facing problem with compiler in usb subject

    i face the error message

    "ERROR: Macro USBINIT? not found in macro file"

    how to solve this problem

    soni

  21. #21
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    if you are german, look at http://www.sprut.de there are the basic for USB & PIC18Fxx55 !
    PBP 2.50C, MCS+ 3.0.0.5, MPLAB 8, MPASM 5.14, ASIX Presto, PoScope, mE mikroBasic V7.2, PICKIT2

  22. #22
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    Quote Originally Posted by robbenaz
    i face the error message

    "ERROR: Macro USBINIT? not found in macro file"

    how to solve this problem

    soni
    Tell us wich PIC you're using and post your code here.
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

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