I finally have this working fairly well. I used Stefan's sample program as a
guide and used classes to define my thread... and that seemed to solve the
crashing issue I was having when trying to write to the LCD from outside the
fast read thread. Here is the current version:
https://github.com/Zaaphod/libusbxhid/blob/Test/WHB04B-4_test.pas
One thing I wasn't able to duplicate however was the use of
EnterCriticalsection(criticalSection); and
LeaveCriticalsection(criticalSection); when writing to shared variables. If I
try to ever use EnterCriticalsection(criticalSection); in the read thread, My
program just instantly locks up and I can't even break out of it. If I try
to use it in the main program I instantly get
EAccessViolation: Access violation
$00007FFF18A2DF23
$00007FFF189E9BBC
$00007FFF189E9AD0
$000000010000DCDA
$000000010000D54B
$000000010000218B PROCESS_USB_DATA, line 475 of WHB04B-4_test.pas
$0000000100002B37 SIMPLETERMINAL, line 641 of WHB04B-4_test.pas
$0000000100002DDD USE_MPG_DEVICE, line 675 of WHB04B-4_test.pas
$0000000100002F93 main, line 699 of WHB04B-4_test.pas
$0000000100002FE6
$0000000100011350
$0000000100001980
$00007FFF17B47E94
$00007FFF18A4A251
Line 475 is EnterCriticalsection(criticalSection);
I left where I had the criticalsection stuff in the program but commented out.
It does seem to work fine without it though.. since the read, I am curious
what I'm doing wrong, or if I need to do something else because I'm on Windows.
Also, there are two versions of this device, once is hard wired to the USB
port, the other is wireless. They both have power buttons on them. When I
turn off the power button on the wireless version, the transceiver still
plugged into the USB port just reports that the device is turned off.. but the
hard wired version just basically unplugs it from the USB port. When this
happens, my read loop generates:
libusbhid_interrupt_read. failed! return code: -1
0libusb: error [winusbx_submit_bulk_transfer] ReadPipe/WritePipe failed: [2]
The system cannot find the file specified.
But I don't really know how I can detect this and exit the process and signal
my other program that the device is no longer present. My read command:
hidReportData[reportIdx].dataLen:=libusbhid_interrupt_read(device_context,$81{endpoint},{out}hidReportData[reportIdx].hid_data,64{report
length, varies by device}, {timeout=}50);
only reports the number of bytes read, and when the device is removed, the
result of the libusbhid_interrupt_read seems to be 64. I’m wondering what the
proper way to gracefully detect the device has been disconnected is so I can
just exit out of the mode the uses the device and return to normal processing
without generating any errors.
Any ideas?
James
-----Original Message-----
From: fpc-pascal <fpc-pascal-boun...@lists.freepascal.org> On Behalf Of Stefan
V. Pantazi
Sent: Friday, August 23, 2019 10:54 AM
To: fpc-pascal@lists.freepascal.org
Subject: Re: [fpc-pascal] USB Human Interface Devices
Thanks for pushing on this. I think any pending timeout/transfer must be
explicitly canceled before closing the USB device, so that the thread can end
gracefully.
The only way I see is to use something like
libusb_handle_events_timeout_completed
http://libusb.sourceforge.net/api-1.0/group__poll.html#ga43e52b912a760b41a0cf8a4a472fbd5b
before closing the USB device context.
That function is not currently part of the libusbx and has a time_t parameter
that appears C-specific but for some reason is not included in ctypes unit. But
I am sure Pascal equivalents can be defined. I will do some tests to include
the libusb_handle_events_timeout_completed in libusbx and libusbhid and let you
know.
On 8/23/19 7:07 AM, James Richters wrote:
> Stefan ,
> Do you get the following errors when you exit your program? Is there some
> way I should shut down the read thread so I don't get this error? I've been
> using a timeout of 0
>
>
> libusb: error [do_close] Device handle closed while transfer was still
> being processed, but the device is still connected as far as we know
> libusb: error [do_close] A cancellation hasn't even been scheduled on
> the transfer for which the device is closing
> libusb: warning [libusb_exit] some libusb_devices were leaked
> Assertion failed!
>
> Program: i:\programming\gcode\libusbxhid\whb04b-4_test.exe
> File: os/poll_windows.c, Line 145
>
> Expression: fd != NULL
> Heap dump by heaptrc unit of
> i:\programming\gcode\libusbxhid\whb04b-4_test.exe
> 50 memory blocks allocated : 1782/1968
> 50 memory blocks freed : 1782/1968
> 0 unfreed memory blocks : 0
> True heap size : 131072 (160 used in System startup) True free heap :
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