uchar to ushort in python

Question

My title might seem strange since there are no such things as uchar and ushort in Python so let me explain : I get a list of 8 bits data from a bulk transfer but I need these in 16 bits. Hence I do this :

frame = dev.read(0x82, packetLength, interface, timeout) # bulk transfer
if len(frame) == packetLength
    for i in range(0, packetLength, 2):
        newFrame.append(frame[i+1]*256 + frame[i])

So yes it works but it is extremely slow and I need to run it on a Raspberry Pi...

Does anyone of you know a better way to do the same thing?

Answer 1

Using struct, the solution would be:

import struct

frame = dev.read( ... )

fmt = "<%dH" % (len(frame) / 2)
newFrame = struct.unpack(fmt, frame)

Explanation of fmt string:

• < - Data is in little-endian format
• %d - The size of your array (it modifies the following format specifier)
• H - Format specifier Interpret the data as ushorts