Acquiring Images from a USB mouse (Single Chip, ADNS-2700) via pyusb

Question

I would like to extract the actual images captured by a single chip optical mouse sensor, specifically the ADNS-2700. As apposed to the various other tutorials on the internet that use a micro controller to talk to the SPI interface of the imaging chip (like this), the chip I am trying to work with has a USB interface integrated.

ADNS-2700 Datasheet

System: Windows 7, Python2.7, PyUSB 1.0

I have successfully extracted the button presses, velocity, and scroll wheel following this example:

import usb.core
import usb.util

VENDOR_ID = 6447
PRODUCT_ID = 2326

# find the USB device
device = usb.core.find(idVendor=VENDOR_ID,
                       idProduct=PRODUCT_ID)

# use the first/default configuration
device.set_configuration()

# first endpoint
endpoint = device[0][(0,0)][0]

# read a data packet
attempts = 10
data = None
while attempts > 0:
    try:
        data = device.read(endpoint.bEndpointAddress,
                           endpoint.wMaxPacketSize)
        print data

    except usb.core.USBError as e:
        data = None
        if e.args == ('Operation timed out',):
            attempts -= 1
            continue

Which extracts data like:

array('B', [0, 0, 16, 0, 0])
array('B', [0, 0, 240, 255, 0])
array('B', [0, 0, 16, 0, 0])
array('B', [0, 0, 240, 255, 0])

---

I need help extracting the raw image data!

I am a USB noob which is probably causing most of the problem.

On page 18 of the datasheet, there is a list of USB commands. The one that looks promising is:

Mnemonic            Command                    Notes
---------------------------------------------------------------
Get_Vendor_Test     C0 01 00 00 xx 00 01 00    Read register xx

Then on page 28, there is a list of registers of which this looks promising:

Address     Register Name    Register Type    Access       Reset Value
----------------------------------------------------------------------
0x0D        PIX_GRAB         Device           Read only    0x00

However, I have tried:

device.write(endpoint.bEndpointAddress,'C0:01:00:00:0A:00:01:00',0)

which results in a:

usb.core.USBError: [Errno None] libusb0-dll:err [_usb_setup_async] invalid endpoint 0x81

as well as:

device.read(endpoint.bEndpointAddress, 0x0D)

which simply times out.

---

Complete Solution:

import usb.core
import usb.util
import matplotlib.pyplot as plt
import numpy as np

VENDOR_ID = 6447
PRODUCT_ID = 2326

# find the USB device
device = usb.core.find(idVendor=VENDOR_ID,
                       idProduct=PRODUCT_ID)

# use the first/default configuration
device.set_configuration()


# In order to read the pixel bytes, reset PIX_GRAB by sending a write command
response = self.device.ctrl_transfer(bmRequestType = 0x40, #Write
                                     bRequest = 0x01,
                                     wValue = 0x0000,
                                     wIndex = 0x0D, #PIX_GRAB register value
                                     data_or_wLength = None
                                     )

# Read all the pixels (360 in this chip)
pixList = []
for i in range(361):
    response = self.device.ctrl_transfer(bmRequestType = 0xC0, #Read
                                         bRequest = 0x01,
                                         wValue = 0x0000,
                                         wIndex = 0x0D, #PIX_GRAB register value
                                         data_or_wLength = 1
                                         )
    pixList.append(response)

pixelArray = np.asarray(pixList)
pixelArray = pixelArray.reshape((19,19))

plt.imshow(pixelArray)
plt.show()

Answer 1

You probably need to do ctrl_transfer() as shown in pyUSB tutorial.

You will also need to convert hex bytes from the datasheet into individual parameters to ctrl_transfer. See this page for the format.

Get_Vendor_Test C0 01 00 00 xx 00 01 00 can be issued with ctrl_transfer() call like this:

ret = dev.ctrl_transfer(bmRequestType=0xc0, # byte[0]
                        bRequest=0x01,      # byte[1]
                        wValue=0x0000,      # byte[2,3]
                        wIndex=register,    # byte[4,5]
                        data_or_wLength = 1)# byte[6,7]