Re: [pyusb-users] Writing and reading hexadecimal command

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Raphaël,

To convert numerical values to byte strings, and vice versa, please use 
the struct API :
import struct
s = struct.pack("<BL", 0, 5)
v1, v2 = struct.unpack("<BL", s)

Please see the struct help for further details.

Nicolas

Le 21/11/2019 à 12:00, raphael moreau a écrit :
>
>  Bonjour,
>
> Thank you for your answer,
>
> The DP5_Programmer's guide can be found here:
>
> http://experimentationlab.berkeley.edu/sites/default/files/images/DP5_Programmers_Guide_A4.pdf
>
> And the entire code is here (Python_SDK\pyDppUSB):
>
> https://www.amptek.com/-/media/ametekamptek/documents/softwares/Python_SDK.zip?la=en
>
> I run the pyDP5.py module (Python_SDK\pyDppUSB\pyDP5.py), and here is 
> a selected part (from Python_SDK\pyDppUSB\DppLibusb.py) that I'm 
> interested in. As I said, this code was provide by Amptek when I 
> contacted them, but it's for demo only in python 2, and not offically 
> supported (that's the reason why it's pretty "dirty", with the few 
> correction I already added):
>
> from vbfunctions import *
> from vbclasses import *
> import usb
> import sys
> import time
> from dppStatus import *
> import codecs
>
> decode_hex = codecs.getdecoder("hex_codec")
>
> LIBUSB_TIMEOUT = 500
>
> #REQUEST_STATUS_PACKET = 
> decode_hex('F5FA01010000FE0F')                  # Request Status Packet
> REQUEST_STATUS_PACKET = '\xf5\xfa\x01\x01\x00\x00\xfe\x0f'
>
>
> #-------------------------------------------------------------------------------
> # DppLibusb Class
> #-------------------------------------------------------------------------------
>
> class DppLibusb():
>     def __init__(self):
>         self.VENDOR = 0x10C4
>         self.PRODUCT = 0x842A
>         self.CONFIGURATION = 1
>         self.INTERFACE = 0
>         self.ENDPOINT_IN = 0x81
>         self.ENDPOINT_OUT = 0x02
>
>         self.device = None
>         self.handle = None
>
>         self.device = usb.core.find(idVendor=0x10c4, idProduct=0x842a)
>
>         #for bus in usb.busses():
>         #   for dev in bus.devices:
>         #      if dev.idVendor == self.VENDOR and dev.idProduct == 
> self.PRODUCT:
>         #         self.device = dev
>
>         self.strStatus = str()
>         self.bArrStatusIn = bytes()
>         self.bArrBuffer = bytes()
>         self.AckPid2 = bytes()
>         self.AckMsg = str()
>         #self.STATUS = STATUS
>         self.DataRaw = bytes()
>         self.Channels = int()
>         self.Data = int()
>         self.Header = bytes()
>
>         self.bArrArrBuffer = bytearray()
>
>         if self.open() == None:
>             print (sys.stderr, "Unable to open DppLibusb device!")
>             sys.exit()
>         return None
>
>     def isConnected(self):
>         _ret = False
>         iNumBytes = 0
>         print("Get Status")
>
> *try:*
> *            iNumBytes = self.write(REQUEST_STATUS_PACKET, 
> LIBUSB_TIMEOUT)*
> **
> *        except usb.USBError as err:*
> *            pass*
> *        if iNumBytes  > 0:*
> *            print ('Bytes Out =',iNumBytes)     # debug*
> *            try:*
> **
> *                self.bArrArrBuffer = self.read(128, LIBUSB_TIMEOUT)*
> *                self.bArrStatusIn = bytearray(self.bArrArrBuffer)*
> **
> *            except usb.USBError as err:*
> *                pass*
>
>
>             if len(self.bArrStatusIn) > 0:
>                 print ("STATUS.RAW type ", type(self.STATUS.RAW))
>                 self.STATUS.RAW = bytearray(self.bArrStatusIn[6:70])
>                 if len(self.STATUS.RAW) > 0:
>                     Process_Status(self.STATUS)
>                     if (self.STATUS.SerialNumber > 0):
>                         _ret = True
>         return _ret
>
> While the iNumbytes get a value from the *iNumBytes = 
> self.write(REQUEST_STATUS_PACKET, LIBUSB_TIMEOUT)* (which might be a 
> wrong value), the *self.bArrArrBuffer = self.read(128, 
> LIBUSB_TIMEOUT)* is never reached. So my guess is that the 
> REQUEST_STATUS_PACKET is in the wrong format, thus my original 
> question : how do I write and read instruction in hexadecimal ? Is 
> converting the whole instruction in string via REQUEST_STATUS_PACKET = 
> '\xf5\xfa\x01\x01\x00\x00\xfe\x0f' correct ? (I doubt it is). Again, 
> sorry for the "messy" code, and thanks for any answer provided.
>
> Best regards
>
> Raphaël
>
>     > Message du 21/11/19 10:11
>     > De : "Nicolas Pinault via pyusb-users"
>     <pyu...@li...>
>     > A : pyu...@li...
>     > Copie à : "Nicolas Pinault" <nic...@aa...>
>     > Objet : Re: [pyusb-users] Writing and reading hexadecimal command
>     >
>     >
>     Bonjour Raphaël,
>     >
>     > You do not provide enought information.
>     > Can you provide a link to the DP5 documentation ?
>     > Can you provide a small code sample ?
>     >
>     > Bonne journée,
>     > Nicolas
>     >
>     >
>     > Le 21/11/2019 à 09:43, raphael moreau a écrit :
>     >
>
>         > Good morning pyusb users,
>
>         >
>
>         > I'm writing you this emial because I'm facing an issue that
>         I did not succed to resolve until now, and I'm sure you will.
>
>         >
>
>         > I'm currently working on a Python project which involve the
>         communication witn an USB Device (DP5 Amptek SDD Detector, an
>         x-ray detector), and after a few test it seems that my device
>         dont understand what I'm telling him to do.
>
>         >
>
>         > I started with the basic, a Device Status request, which is
>         the following (.jgp screenshot, I hope you'll be able to see it):
>
>         >
>
>         >
>
>         > I tried the classic dev.write(x,test,x), with test =
>         '\xf5\xfa\x01\x01\x00\x00\xfe\x0f', or test =
>         '\xf5\xfa1100\xfe\x0f' but the expected result, which is the
>         following(same here, .jpg screenshot):
>
>         >
>
>         >
>
>         > does not seems to be return with res = dev.read(x, length,
>         x) with length = 128 or length = 64 (seems odd to me for the
>         128 but i guess it's for the array format?)
>
>         >
>
>         >
>
>         > My question is therefore quit simple, how do I pass and read
>         thoses command ?
>
>         >
>
>         > I'm using python 3, and I have no problem in term of
>         identification of the device, configuration, interface and
>         endpoint IN and OUT, with pyusb.
>
>         >
>
>         > The program I'm using is an old python 2 demo supplied by
>         the manufacturer which is not supported by them.
>
>         > I precise that I'm rather new to USB and programming in
>         general, so I apologize if this question seems basic, or had
>         already been answered to.
>
>         >
>
>         > Thank you for any response,
>
>         >
>
>         > Best regards,
>
>         >
>
>         >
>
>         >
>
>         > Raphaël Moreau
>
>         >
>
>         >
>
>         >
>
>         >
>
>
>         >
>
>
>         >
>
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>
>
>
>
>
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