Software on PIC will come in loop after disconnect USB connection

[Darrel Taylor]

Yup, you 2 were right. It only picked up the Plugged, not the un-plugged state.

After a bit of re-thinking, ...
This seems to work pretty good.

The way it works is by watching the IDLEIF and SOFIF interrupt flags.
IDLEIF is triggered if the USB buss is idle for more than 3ms.
SOFIF is the Start-Of-Frame flag, which is a good indication of buss activity.

If it sees a SOFIF it sets the Plugged bit, and if it sees an IDLEIF flag it clears the Plugged bit.
Then in the Main loop you can use that flag to stop sending data if not Plugged.

This example uses Interrupts, but you can do the same thing without interrupts, just be sure to check for the flags before servicing USB.
The example turns on LED1 when Plugged, and toggles a second LED to show that the Main loop keeps executing when un-plugged.

DEFINE OSC 48          
CLEAR

INCLUDE "DT_INTS-18.bas"    ' Base Interrupt System

ASM
INT_LIST  macro    ; IntSource,          Label,  Type, ResetFlag?
        INT_Handler    USB_INT,  _DoUSBService,   ASM,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
endasm

UIE     VAR BYTE EXT
UEIE    VAR BYTE EXT
UIR     VAR BYTE EXT
IDLEIF  VAR UIR.4
SOFIF   VAR UIR.6
Plugged VAR BIT 

LED1    VAR  PORTB.0 : LOW LED1
LED2    VAR  PORTC.1 : LOW LED2


USBBufferCount  Var Byte
DataToSend      var byte[8]
USBBufferCount = 8

pause 500 ' initialise USB...
usbinit
usbservice
UIE = $7F
UEIE = $9F
@   INT_ENABLE  USB_INT

;----[Main program starts here]-----------------------------------------------
Main:
    LED1 = Plugged        ; LED1 indicates OK to Send
    IF Plugged then       ; if bus available, transmit data
        USBOut 1, DataToSend, USBBufferCount, Main  
    ENDIF
    toggle LED2           ; blink LED2 to show Main Loop is still running
    pause 100    
goto Main                                     

;----[USB Interrupt Handler]--------------------------------------------------
DoUSBService:
    IF IDLEIF THEN Plugged = 0
    IF SOFIF  THEN Plugged = 1
    usbservice
@   INT_RETURN

HTH,

[Squibcakes]

Hi DT,

Great! I tried this one and it works. Good one.

However, I've tried to incorp. it into an existing program and it doesn't work.

Your code seems to indicate that the USBSERVICE routine is continually called by the USB_int handler. How often does this interrupt? Only when it is plugged / unplugged or all the time?

The problem is that I'm servicing the USBSERVICE through a 1msec Timer1 interrupt handler and trying to read the flags in that interrupt but they don't set.

'---[TMR1 - interrupt handler]---------------------------------------------------
USB_SERVICE:                    ' COMES HERE 1msec TO SERVICE THE USB PORT
        
     T1CON.0 = 0                ' TURN OFF TIMER                 
        TMR1L = COUNTER1.byte0  ' RELOAD TIMER  LOW
        TMR1H = COUNTER1.byte1  ' RELOAD TIMER HIGH
        IF IDLEIF THEN Plugged = 0
        IF SOFIF  THEN Plugged = 1
        USBService	            ' KEEP USB ALIVE
     T1CON.0 = 1                ' TURN ON TIMER
    
    
@ INT_RETURN

The way I see it is that SOFIF should always be set since I'm servicing USB every 1 msec untill I disconnect the USB cable.

I would do away with the Timer1 Interrupt altogether and use USB_INT but how often does the USB_int get called?


Cheers
Squib

[Darrel Taylor]

Using the USB_INT source is much more efficient than using a 1ms timer.

During Enumeration it may only be a few microseconds between interrupts, and there are a lot of them. Consequently, it connects to the PC much faster.

But during normal operation, it drops to about every 10-20 milliseconds, although that depends on the polling time set up in the descriptor.

When the cable is un-plugged, you don't get any USB interrupts at all (after the IDLE int).

Plus using the USB_INT frees up a Timer.

ADDED:

But that doesn't explain why the Plugged example above doesn't work with the Timer Interrupts. It should work.

Are there any other USBSERVICE statements in the program?
There should only be 1.

[Squibcakes]

DT,

What you say makes sense and I like the fact that it frees up a Timer.

I found in my original program that I missed (during a cut and paste) the section where you loaded UIE and UEIE with values... which would explain why it wasn't running with my timer ints....

The whole point of this exercise is to "error trap" the pic for any unforseen conditions, eg I've seen the PIC hang sometimes when shutting down pc coms programs that don't close the port nicely. Hopefully this will stamp that one out. LOL

Now, since you have all the answers, do you have tonight's Lotto Numbers by any chance?

Cheers
Squib

[Darrel Taylor]

... do you have tonight's Lotto Numbers by any chance? ...

Oh sure ... Here's the numbers for California's Super Lotto Plus, for all future draws.
Just come back here before each game for the new numbers.



Of course it would have been better, had you asked for "tonight's Winning Lotto Numbers"!

[Art]

Lol,
NVM. if the game is played long enough, they'll win at some stage.