From your example it looks like you placed the device reading
(interrupt read) and writing (set report) into the same read thread. I
thought keeping them separate was a good idea: tight loop reads and
less frequent writes (LCD updates).
Libusb is supposed to be thread-safe. Not really an issue for your app
but if you need to make sure only one thread out of multiple threads is
processing libusb events the library has asynchronous API that does
offer locking functionality.
On 8/21/19 3:48 PM, James Richters wrote:
Well.. It doesn’t always work just reading constantly and writing in a
different thread..
So I have my fast read loop always reading then my LCD write loop sending the 3
packets every 0.3 Seconds.. and it functions ok, and I don’t miss too many
counts... but every so often I get this message:
libusb: warning [handle_timeout] async cancel failed -5 errno=0
I have a timeout on my read loop of 10ms. I tried setting that to 0 so it
would just wait for input in it's thread.. but when I do that I get this as
soon as I attempt to write to it:
An unhandled exception occurred at $00007FFF189F03C6:
EAccessViolation: Access violation
$00007FFF189F03C6
$00007FFF189EDA21
$00007FFF17AAA1A1
$00007FFF17AA9CB5
$000000006B607FFB
$000000006B6081E7
$000000006B60C695
$000000006B605D6F
$000000006B607E40
$000000010001B1CA
$00000001000021BF main, line 445 of whb04b-4_test.pas
$00000001000022B6
$000000010000EC20
$0000000100001880
$00007FFF17B47E94
$00007FFF18A4A251
Also if I put in a really long timeout like 1000ms I get that. Line 445 is
libusbhid_set_report(device_context, HID_REPORT_TYPE_FEATURE, $6 , 8 ,
WhB04_Packet1 );
so I can't write while I'm reading or waiting for a read after all.
So I came up with a scheme to set all the variables in the slow loop then set a
Boolean variable when it's done.. then the fast loop checks for the flag if it
is idle for a time, meaning it's not trying to keep up with input.. and that
does work.. and I don't miss many counts... but it does miss a few... but I
STILL get this
libusb: warning [handle_timeout] async cancel failed -5 errno=0
even though as far as I can tell, I can't possible be reading and writing at
the same time.
I've updated my test project here:
https://github.com/Zaaphod/libusbxhid/blob/master/WHB04B-4_test.pas
I don't really know what libusb: warning [handle_timeout] async cancel failed
-5 errno=0 is trying to tell me... it is having an issue canceling waiting for
data after the time out I guess.. but why is that a problem?
Any Ideas?
James
-----Original Message-----
From: fpc-pascal <fpc-pascal-boun...@lists.freepascal.org> On Behalf Of James
Richters
Sent: Wednesday, August 21, 2019 8:30 AM
To: 'FPC-Pascal users discussions' <fpc-pascal@lists.freepascal.org>
Subject: Re: [fpc-pascal] USB Human Interface Devices
I FINALLY wrote some data to the LCD!! YAY !!! I was trying to get the
python application to work.. without any luck.. but I ended up going ahead and
trying Zadig changing the driver to libusb-win32... After I gave up on Python,
I went back to FPC and just ran my existing sample program, and I noticed where
it used have an error sending to device, it now said 8 bytes sent!! It's very
strange I could read it just fine but not write to it without messing with the
driver... but it's working now!
I tried suspending the read thread to write to it.. and well it must have ended
up suspending in the middle of a read because the whole thing locked up.. so I
just tried as suggested and let it keep reading in a tight loop in it's own
thread and then just throw in a write every few seconds on the main program..
and that actually worked fine.. I guess libusb takes care of worry about
finishing a read before writing.. I think I did see libusb had something to do
with threads.
So now it's just a matter of small details. The display is a little odd...
in that instead of sending it just a real number, you send it an integer for
the numbers before the decimal and another integer for the numbers after the
decimal.. but it's 2 bytes for each (4 bytes total) but they are in reverse
order.. I need to send LowByte_Integer, High_Byte_Integer, LowByte_decimal,
High_Byte_decimal so the bits from a 16 bit integer end up being
76543210,FEDCBA98 I think this is that edian byte order thing that was
mentioned. I'm just curious if there is already a function available to
reverse these like this.. or if I just need to write my own. It's just some
rotates and then split it, so I can do that, but I'm just wondering if there is
something already there to do this.. I seem to recall that this kind of thing
needs to happen quite a bit.
Also I need to stick a $06 in front of all my packets to send to the device. I
have my data all in arrays, so I want to do something like this
Device_Array[0]:=$06; Device_Array[1..7] := LCD_Array[0..6] ;
Ah.. but that doesn't work.. is there a way to do this with syntax or do I just
need to make a loop to copy the array elements the way they need to be?
James
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