I figured this was a small change so I commited it. Some of my samples will
implement something like this to check if USB is connected or not. This way
there is no need to poll USB quickly while USB is not connected.
-- define procedures and variables
procedure usb_disconnected_tasks()
procedure usb_connected_tasks()
var word char_count = 0
var word usb_check = 0
var byte usb_connected = TRUE
-- main loop to serve USB
forever loop
-- poll the usb ISR function on a regular base, in order to
-- serve the USB MSD requests
usb_msd_tasks()
-- Check if usb is still connected
-- Another way would be to check the voltage on a USB+ pin.
if USB_EVENT_OCCURRED == 1 then
usb_check = 0
elsif usb_check == 0xFFFF then
-- USB is not connected
usb_disconnected_tasks() -- perform your tasks
else
-- USB is connected
usb_connected_tasks() -- tasks while connected
usb_check = usb_check + 1
end if
end loop
-- Do anything you want here while usb is disconnected.
-- Quit the procedure when USB_EVENT_OCCURRED = 1
procedure usb_disconnected_tasks() is
if usb_connected == TRUE then
print_crlf(serial_data)
print_string(serial_data, "USB is disconnected." )
usb_connected = FALSE
end if
forever loop
serial_data = "!"
delay_1s(1)
if USB_EVENT_OCCURRED == 1 then
exit loop
end if
end loop
end procedure
-- Do anything you want here while usb is connected, but don't take long!
procedure usb_connected_tasks() is
if usb_connected == FALSE then
;-- wait till MSD is configured
usb_msd_wait_configured()
print_crlf(serial_data)
print_string(serial_data, "USB is connected." )
usb_connected = TRUE
end if
-- poll the usb ISR function on a regular base, in order to
-- serve the USB MSD requests
usb_msd_tasks()
-- let us know the PIC is actually doing something
-- by sending char "." to serial port
if char_count == 40000 then
serial_data = "."
_usec_delay(100)
char_count = 0
end if
char_count = char_count + 1
end procedure
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