[pyusb-users] PyUSB for isochronous transfert

[Prince A. RAMAHEFA-A. <pri...@gm...>]

> That is not true for bulk mode. You should be able to ac> hieve
> 2Mbit/s using bulk transfer.


In fact, my project consist in sending digital value of a sampled
analog signal (sample rate = 160kHz, 16bits ADC) to a PC via USB.

Can I reach a 3Mbits/s data rate (useful data) with bulk transfert ?
if no, How can I do as a transfert with PyUSB ?

And if I can do this, can you give a sample code in Python (PyUSB) if
I want to read a data without interruption.

Otherwise, I've tested this code to determine the time that 1000*64
bytes to be transmitted:

import time
import usb.util
import usb.backend
import os
import sys
from usb import *
import ctypes
from ctypes import c_ubyte

import time

alternate_setting = c_ubyte(0)
ep_write=0x01
ep_read = 0x81

buffer_size = 64
#buffer_size = 512

# find our device
dev = usb.core.find(idVendor=0x04D8, idProduct=0x0204)

# was it found?
if dev is None:
    raise ValueError('Device not found')

# set the active configuration. With no arguments, the first
# configuration will be the active one
dev.set_configuration()

# get an endpoint instance
cfg = dev.get_active_configuration()

i = 0
d1 = time.time()
N = 1000
while i<N:
    data = dev.read(ep_read, buffer_size, 0, timeout = None)
    i = i+1

d2 = time.time()
print 'time ',d2-d1, 'for', N*buffer_size, 'so', (N*buffer_size)/(d2-d1)


And I have this before execution :
************* time  1.04299998283 for 64000 so 61361.4583445

so the maximum data rate is around 64kByte/s for Bulk

So, I can't reach 3Mbits/s. isn't it ?

Thank you very much.

----------------------
Arnaud