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Sending USB commands with Python

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  Sending USB commands with Python "Adam W." <AWasilenko@gmail.com> - 2012-08-28 17:04 -0700
    Re: Sending USB commands with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-28 22:54 -0400
      Re: Sending USB commands with Python hamilton <hamilton@nothere.com> - 2012-08-28 21:03 -0600
        Re: Sending USB commands with Python alex23 <wuwei23@gmail.com> - 2012-08-28 22:04 -0700
          Re: Sending USB commands with Python hamilton <hamilton@nothere.com> - 2012-08-28 23:18 -0600
    Re: Sending USB commands with Python Tim Roberts <timr@probo.com> - 2012-08-28 23:45 -0700
      Re: Sending USB commands with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-29 16:09 -0400
        Re: Sending USB commands with Python "Adam W." <AWasilenko@gmail.com> - 2012-08-29 14:21 -0700
          Re: Sending USB commands with Python Tim Roberts <timr@probo.com> - 2012-08-30 20:55 -0700
        Re: Sending USB commands with Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-29 17:57 -0400

#28036 — Sending USB commands with Python

So I'm trying to get as low level as I can with my Dymo label printer, and this method described the PDF http://sites.dymo.com/Documents/LW450_Series_Technical_Reference.pdf seems to be it.

I'm unfamiliar with dealing with the USB interface and would greatly appreciate it if someone could tell me how to send and receive these commands with Python.  Perhaps if you were feeling generous and wanted to write a bit of sample code, sending the "Get Printer Status" command and receiving the response (page 17 of the PDF) would be perfect to get me on my way.

Thanks,
Adam

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#28040

On Tue, 28 Aug 2012 17:04:49 -0700 (PDT), "Adam W."
<AWasilenko@gmail.com> declaimed the following in
gmane.comp.python.general:

> So I'm trying to get as low level as I can with my Dymo label printer, and this method described the PDF http://sites.dymo.com/Documents/LW450_Series_Technical_Reference.pdf seems to be it.
> 
> I'm unfamiliar with dealing with the USB interface and would greatly appreciate it if someone could tell me how to send and receive these commands with Python.  Perhaps if you were feeling generous and wanted to write a bit of sample code, sending the "Get Printer Status" command and receiving the response (page 17 of the PDF) would be perfect to get me on my way.
> 

1)		what OS?

2)		does the printer appear as a serial port by the OS? Or as a
printer device?

	If it appears as a serial port, you may want to obtain the pyserial
(or whatever the name is this year) package. For USB, you may need one
of the variant USB packages (pywinusb, pyusb, etc.) With luck you won't
need to use admin privileges to access the port as a raw device vs
having to go through an OS driver...


-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#28041

On 8/28/2012 8:54 PM, Dennis Lee Bieber wrote:
> 2)		does the printer appear as a serial port by the OS? Or as a
> printer device?

The OP posted the link to the manual.

If your not going to at least look it over, .........


USB Printer Interface

The LabelWriter 450 series printers all communicate with the host 
computer using a full-speed USB 2.0 interface. This interface also 
operates with USB Version 1.1 or later. The printers implement the 
standard USB Printer Class Device interface for communications (see 
http://www.usb.org/developers/devclass/).

hamilton

PS: Page 14

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#28045

On Aug 29, 1:03 pm, hamilton <hamil...@nothere.com> wrote:
> The OP posted the link to the manual.
> If your not going to at least look it over, .........

Speaking for myself, I _don't_ go out of my way to read extra material
to help someone with a problem here. If it's worth mentioning, mention
it in the question.

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#28046

On 8/28/2012 11:04 PM, alex23 wrote:
> On Aug 29, 1:03 pm, hamilton <hamil...@nothere.com> wrote:
>> The OP posted the link to the manual.
>> If your not going to at least look it over, .........
>
> Speaking for myself, I _don't_ go out of my way to read extra material

But, you will give advice that has no value.


Anything you post here from now on will be suspect.

hamilton

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#28048

"Adam W." <AWasilenko@gmail.com> wrote:
>
>So I'm trying to get as low level as I can with my Dymo label printer, 
>and this method described the PDF 
>http://sites.dymo.com/Documents/LW450_Series_Technical_Reference.pdf 
>seems to be it.
>
>I'm unfamiliar with dealing with the USB interface and would greatly
>appreciate it if someone could tell me how to send and receive these
>commands with Python.  Perhaps if you were feeling generous and 
>wanted to write a bit of sample code, sending the "Get Printer 
>Status" command and receiving the response (page 17 of the PDF) 
>would be perfect to get me on my way.

Well, it's more than "a bit of sample code".  You would essentially be
writing a device driver.

Which operating system are you using?  If you are on Windows, then the
operating system has already loaded a printer driver for this device.  You
can't talk to the USB pipes without uninstalling that driver.  It would be
just about as easy for you to learn to use GDI to write to the printer like
a normal application, and that way the code would work on the NEXT
generation of printer, too.

The libusb or libusbx libraries can be used to talk to USB devices.  There
is a Python binding.  On Windows, you still need to have a driver, but the
libusbx instructions can help you find an install one.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

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#28071

On Wed, 29 Aug 2012 05:47:00 -0700 (PDT), "Adam W."
<AWasilenko@gmail.com> declaimed the following in
gmane.comp.python.general:

> 
> Trying to do the status thing mentioned before, in the interpreter I did:
> 
> >>> ep.write('A')
> 2
> 

	Don't the commands require an <esc> character? "\x1BA" (or
"\x1B\x41")

	OTOH, if the <esc> is issued behind the scenes,

> And the manual says 2 is not a valid option... So something isn't adding up.

 ... and you do not need to issue some sort of read(), page 17 of the
printer manual you linked would translate to 

not ready, top of form, not out of paper, not jammed, not in error

	Granted, page 10 implies that the printer will never show "not
ready"

	However -- reading the pyUSB source code

-=-=-=-=-
 def write(self, data, timeout = None):
        r"""Write data to the endpoint.
        
        The parameter data contains the data to be sent to the endpoint
and
        timeout is the time limit of the operation. The transfer type
and
        endpoint address are automatically inferred.

        The method returns the number of bytes written.

        For details, see the Device.write() method.
        """
        return self.device.write(self.bEndpointAddress, data,
self.interface, timeout)
-=-=-=-=-

indicates that the "2" you are seeing is the "number of bytes written";
you need to issue a read request to retrieve the returned printer
status.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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#28072

On Wednesday, August 29, 2012 4:09:49 PM UTC-4, Dennis Lee Bieber wrote:
>
> 	Don't the commands require an <esc> character? "\x1BA" (or
>    "\x1B\x41")
> 
> 	OTOH, if the <esc> is issued behind the scenes,

I'm not sure which esc char it is asking for, I don't think libusb is providing its own, and it seems like the one you suggested isn't what it wants either..

>  ... and you do not need to issue some sort of read()
> the "2" you are seeing is the "number of bytes written";
> 
> you need to issue a read request to retrieve the returned printer
> 
> status.
> 

You are correct about the 2 being the number of bytes written.  However when I issue a read command I get:

>>> ep.write('\x1BA')
4
>>> ep.read(1)
Traceback (most recent call last):
  File "<pyshell#75>", line 1, in <module>
    ep.read(1)
  File "C:\Python32\lib\site-packages\usb\core.py", line 301, in read
    return self.device.read(self.bEndpointAddress, size, self.interface, timeout)
  File "C:\Python32\lib\site-packages\usb\core.py", line 654, in read
    self.__get_timeout(timeout)
  File "C:\Python32\lib\site-packages\usb\backend\libusb01.py", line 483, in bulk_read
    timeout)
  File "C:\Python32\lib\site-packages\usb\backend\libusb01.py", line 568, in __read
    timeout
  File "C:\Python32\lib\site-packages\usb\backend\libusb01.py", line 384, in _check
    raise USBError(errmsg, ret)
usb.core.USBError: [Errno None] b'libusb0-dll:err [_usb_setup_async] invalid endpoint 0x02\n'

Avoiding the read command all together I should be able to write "<esc> E" and have it feed some paper, which it is not doing, so obviously there is more to uncover.  That said I feel this endeavor has evolved and is no longer pertinent to the Python group so I will let you guys off the hook on this (although responses/suggestions are still welcome).

Thanks for all your help!

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#28158

"Adam W." <AWasilenko@gmail.com> wrote:
>
>You are correct about the 2 being the number of bytes written.  However when I issue a read command I get:
>
>>>> ep.write('\x1BA')
>4
>>>> ep.read(1)
>usb.core.USBError: [Errno None] b'libusb0-dll:err [_usb_setup_async] invalid endpoint 0x02\n'

USB endponts only go in one direction.  There will be one endpoint for
outoging data, and one endpoint for incoming data.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.

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#28075

On Wed, 29 Aug 2012 14:21:30 -0700 (PDT), "Adam W."
<AWasilenko@gmail.com> declaimed the following in
gmane.comp.python.general:

> You are correct about the 2 being the number of bytes written.  However when I issue a read command I get:
> 
> >>> ep.write('\x1BA')
> 4

	That's interesting -- as if each byte you send is expanding into a
pair of bytes.

> >>> ep.read(1)
> Traceback (most recent call last):
>   File "<pyshell#75>", line 1, in <module>
>     ep.read(1)
>   File "C:\Python32\lib\site-packages\usb\core.py", line 301, in read
>     return self.device.read(self.bEndpointAddress, size, self.interface, timeout)
>   File "C:\Python32\lib\site-packages\usb\core.py", line 654, in read
>     self.__get_timeout(timeout)
>   File "C:\Python32\lib\site-packages\usb\backend\libusb01.py", line 483, in bulk_read
>     timeout)
>   File "C:\Python32\lib\site-packages\usb\backend\libusb01.py", line 568, in __read
>     timeout
>   File "C:\Python32\lib\site-packages\usb\backend\libusb01.py", line 384, in _check
>     raise USBError(errmsg, ret)
> usb.core.USBError: [Errno None] b'libusb0-dll:err [_usb_setup_async] invalid endpoint 0x02\n'
> 
> Avoiding the read command all together I should be able to write "<esc> E" and have it feed some paper, which it is not doing, so obviously there is more to uncover.  That said I feel this endeavor has evolved and is no longer pertinent to the Python group so I will let you guys off the hook on this (although responses/suggestions are still welcome).
> 

	Your original code shows you matching to an "OUT" endpoint... Could
you need an "IN" to read the return values?

	Unfortunately it will be a few weeks before Amazon ships "USB
Complete" so most of the setup hassle is currently just noise to me.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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