Pic 18f Usb

[Bruce]

Steve,

You're dealing with bytes. PORTA.1 = USBBuffer[1] isn't the way to go since you can't place a byte value on a single port "bit".

Just place the byte you need on the whole port. You can send a single byte value from the PC app, and simply place it on the port.

I.E. PORTA = USBBuffer[1] should work fine - assuming that's the byte element you want.

Sending data from the PIC to PC is equally simple. Here's one example. Note this isn't everything. Just the sections I added to the framework file created with EasyHID.

DEFINE OSC 48
DEFINE LOADER_USED 1
DEFINE	ADC_BITS 10     ' Set number of bits in result
DEFINE	ADC_CLOCK 3     ' Set clock source /32
DEFINE	ADC_SAMPLEUS 50 ' Set sampling time in uS
DEFINE RESET_ORG 800h ' <-- I used the Microchip USB loader

BufferSize      con 8
DataBuffer      Var Byte(BufferSize) ' data buffer
DataBufferCount Var Byte             ' buffer size
Quanta  con 1251
TRISD = 0
PORTD = 0

' Variables
X       VAR byte
Adval   VAR WORD
   
    TRISA.0 = 1        ' RA0 input
    ADCON1 = %00001110 ' A/D channel 0
    ADCON2 = %10000011 ' Right justify for 10-bit
    USBInit

Main:
    GOSUB DoUSBIn
    PORTD = DataBuffer[7]
    
    ADCIN 0,adval		     ' Read A/D channel 0 into ADval variable
    ADval = ADval */ Quanta  ' Quanta result
    
    ' Load data buffer
    DataBuffer(0) = Adval DIG 3
    DataBuffer(1) = "."
    DataBuffer(2) = Adval DIG 2
    DataBuffer(3) = Adval DIG 1
    DataBuffer(4) = Adval DIG 0
    GOSUB DoUSBOut
    FOR X = 0 to 99 ' Short delay between updates
     PAUSEUS 1000
     USBSERVICE     ' Maintain HID connection during delay period
    NEXT X
    GOTO Main

On the PC side, modify the USB framework file created with EasyHID something like this;
Dim MyText As String ' create your string storage space

In the OnRead sub-routine;
MyText = (CStr(BufferIn(1)) + Chr$(BufferIn(2)) + CStr(BufferIn(3)) + CStr(BufferIn(4)) + CStr(BufferIn(5)) + "V")
Label1.Caption = MyText ' Place string text into label displaying A/D value

Judy,

Reading three pulse widths or A/D values doesn't really have anything to do with USB. The USB PIC is just another PIC with the addition of the USB module. Using the onboard A/D is pretty much the same as any other PIC.

All you need here is the datasheet, and a little time to experiment getting your pulse measurement & A/D routines working. Sending this all to the PC via the USB module is no more than stuffing your values into the outgoing buffer like in the previous example.

Just be sure to keep the USB connection alive by avoiding the use of blocking functions, long delays, etc,,. It's really not that hard, but you will need to experiment a tad.

[Tissy]

Bruce,

Would you mind posting all of your ADC code, i am getting errors. I've had a look, but can't figure it out.

The code posted above seems to be missing the DoUSBIn and DoUSBOut subroutines.

I also get an error on the DataBuffer(1) = "."

I want to use it as a 5v voltage monitor passing the results to Vb.

Many thanks,

Steve

[Bruce]

Hi Steve,

Sure. Here's the complete file. Just be sure you've used EasyHID to generate the required USB support files.

DEFINE LOADER_USED 1
DEFINE OSC 48
DEFINE ADC_BITS 10     ' Set number of bits in result
DEFINE ADC_CLOCK 3     ' Set clock source /32
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS
DEFINE RESET_ORG 800h    ' For Microchip USB loader

BufferSize      con 8
DataBuffer      Var Byte(BufferSize) ' data buffer
DataBufferCount Var Byte             ' buffer size
Quanta  con 1251
TRISD = 0
PORTD = 0

' Variables
X       VAR byte
Adval   VAR WORD
   
    TRISA.0 = 1        ' RA0 input
    ADCON1 = %00001110 ' A/D channel 0
    ADCON2 = %10000011 ' Right justify for 10-bit
    USBInit

Main:
    GOSUB DoUSBIn
    PORTD = DataBuffer[7]
    
    ADCIN 0,Adval		 ' Read A/D channel 0 into ADval variable
    ADval = ADval */ Quanta  ' Quanta result
    
    ' Load data buffer
    DataBuffer(0) = Adval dig 3
    DataBuffer(1) = "."
    DataBuffer(2) = Adval DIG 2
    DataBuffer(3) = Adval DIG 1
    DataBuffer(4) = Adval DIG 0
    GOSUB DoUSBOut
    FOR X = 0 to 99 ' Short delay between updates
     PAUSEUS 1000
     USBSERVICE     ' Maintain HID connection during delay period
    NEXT X
    GOTO Main

   ' USB in...
DoUSBIn:
    DataBufferCount = BufferSize
    USBService
    USBIn 1, DataBuffer, DataBufferCount, DoUSBIn
    RETURN
   
   ' USB out...
DoUSBOut:
    DataBufferCount = BufferSize
    USBService
    USBOut 1, DataBuffer, DataBufferCount, DoUSBOut
    RETURN
    
    END

Here's the PIC & VB source for a USB A/D datalogger http://www.rentron.com/mcstudio/USB_AD.zip

[Tissy]

Great, thanks Bruce. Unfortuanatly i am still getting a big 0 in VB. I'm sure its only something small i am doing wrong (hopefully) !!

Here is the code, can you spot anything obvious that i have done wrong?

Its a PIC18F2455 where i am putting 5v onto RA0.

DEFINE LOADER_USED 1
DEFINE OSC 48
DEFINE ADC_BITS 10     ' Set number of bits in result
DEFINE ADC_CLOCK 3     ' Set clock source /32
DEFINE ADC_SAMPLEUS 50 ' Set sampling time in uS
'DEFINE RESET_ORG 800h    ' For Microchip USB loader

BufferSize      con 8
DataBuffer      Var Byte(BufferSize) ' data buffer
DataBufferCount Var Byte             ' buffer size
Quanta  con 1251


' Variables
X       VAR byte
Adval   VAR WORD
   
    TRISA.0 = 1        ' RA0 input
    ADCON1 = %00001110 ' A/D channel 0
    ADCON2 = %10000011 ' Right justify for 10-bit
    USBInit

Main:
    GOSUB DoUSBIn
    PORTB = DataBuffer[7]
    
    ADCIN 0,Adval		 ' Read A/D channel 0 into ADval variable
    ADval = ADval */ Quanta  ' Quanta result
    
    ' Load data buffer
    DataBuffer(0) = Adval dig 3
    DataBuffer(1) = "."
    DataBuffer(2) = Adval DIG 2
    DataBuffer(3) = Adval DIG 1
    DataBuffer(4) = Adval DIG 0
    GOSUB DoUSBOut
 
    FOR X = 0 to 99 ' Short delay between updates
       PAUSEUS 1000
       USBSERVICE     ' Maintain HID connection during delay period
    NEXT X

 GOTO Main

' ************************************************************
' * receive data from the USB bus                            *
' ************************************************************
DoUSBIn:
    DataBufferCount = BufferSize
    USBService
    USBIn 1, DataBuffer, DataBufferCount, DoUSBIn
    RETURN
   
' ************************************************************
' * wait for USB interface to attach                         *
' ************************************************************
DoUSBOut:
    DataBufferCount = BufferSize
    USBService
    USBOut 1, DataBuffer, DataBufferCount, DoUSBOut
    RETURN
END

In VB, i have placed a label on the form and this is in the read event section

'*****************************************************************
' on read event...
'*****************************************************************
Public Sub OnRead(ByVal pHandle As Long)
   
   ' read the data (don't forget, pass the whole array)...
   If hidRead(pHandle, BufferIn(0)) Then
      
    MyText = (CStr(BufferIn(1)) + Chr$(BufferIn(2)) + CStr(BufferIn(3)) + CStr(BufferIn(4)) + CStr(BufferIn(5)) + "V")
    Label1.Caption = MyText ' Place string text into label displaying A/D value

      
      ' ** YOUR CODE HERE **
      ' first byte is the report ID, e.g. BufferIn(0)
      ' the other bytes are the data from the microcontrolller...
   End If
End Sub

Many thanks again.

Steve

[Bruce]

Private Const VendorID = 6017
Private Const ProductID = 2000

Check to make sure the vendor & product ID numbers in your VB source match the vendor/product ID #'s in the PIC framework files generated by EasyHID. If these don't match, the VB app will never respond.

[Tissy]

Although i have changed the ProductID from 2000 to 2005, the device is recognised.

The VB program displays a text box which says USB Device Connected or indeed Disconnected, depending on its status.

So, i think this bit is OK.

Steve

[Bruce]

What exactly is happening? Are you getting nothing on the label caption? Have you verified your hardware with something simple like reading the A/D input, and displaying the result on an LCD, serial terminal, etc?

[Tissy]

Basically i'm putting 5v on the PORTA.0 pin and just gettin 'label1' in the label of VB.

Should VB always be updating and looking at the USBinput or should there be a READ button thats calls the procedure?

Also on the VB side it has:

MyText = (CStr(BufferIn(1)) + Chr$(BufferIn(2)) + CStr(BufferIn(3)) + CStr(BufferIn(4)) + CStr(BufferIn(5)) + "V")

Most of it contains CStr but the bit thats contains Chr$, i presume thats for the "." as sent from the PIC.

I've tried playing around with it, but still no joy. If you have it, is it worth sending me the vb source file you have just for this bit?

Are you on messenger, i am, i thought it might be easier to converse?

Thanks again,

Steve