rigol.py

"""
Version 1.0a, 29 Jun 13
"""

import usb.core
import usb.util
import sys, array

class Scope:
    #class variables


    #constructor
    def __init__(self, VID, PID, EP_OUT=0x01, EP_IN=0x86):
        self.__vendorId = VID
        self.__productId = PID
        self.__dev = []
        self.bTag = 0x01

    #static methods

    #instance method
    def findDevice(self):
        # find our device
        # idVendor=0x1ab1,idProduct=0x04b0
        #print ("looking for VID: " + self.__vendorId + \
        #" PID: " + self.__productId)
        self.__dev = usb.core.find(idVendor=self.__vendorId, idProduct=self.__productId)
        # was it found?
        if self.__dev is None:
            return False


        # set the active configuration. With no arguments, the first
        # configuration will be the active one
        self.__dev.set_configuration()
        return True

    def write(self, SCPI_command = ""):
        """
        *************************************************************
        Perform a message write
        *************************************************************
        """
        #message ID 1=DEV_DEP_MSG_OUT, 2=REQUEST_DEV_DEP_MSG_IN
        MsgID = 0x01
        # sequential message identifier
        self.bTag += 1
        if (self.bTag > 255):
            self.bTag = 0
        bTagInverse = (self.bTag ^ 0xFF)
        command = bytearray(SCPI_command, 'latin1')
        txSize_0 = (len(command) & 0xFF)
        txSize_1 = (len(command)>>8 & 0xFF)
        txSize_2 = (len(command)>>16 & 0xFF)
        txSize_3 = (len(command)>>24 & 0xFF)
        EOM = 0x01
        bReserved = 0x00

        frame = [MsgID, self.bTag, bTagInverse, bReserved, txSize_0, txSize_1, \
         txSize_2, txSize_3, EOM, bReserved, bReserved, bReserved]

        # add the command
        frame += command

        # pad the frame to 4 byte (32bit) chunks
        while ((len(frame) % 4) > 0):
        	frame += [0x00]

        ret = self.__dev.write(0x02, frame)

    def read(self, no_of_bytes = 0, timeout_ms=100):
        """
        *************************************************************
        Write the read back request giving the device the ability to
        write back to the BULK-IN endpoint
        *************************************************************
        """
        #message ID 1=DEV_DEP_MSG_OUT, 2=REQUEST_DEV_DEP_MSG_IN
        MsgID = 0x02
        # sequential message identifier
        self.bTag += 1
        if (self.bTag > 255):
            self.bTag = 0
        bTagInverse = (self.bTag ^ 0xFF)
        rxSize_0 = (no_of_bytes & 0xFF)
        rxSize_1 = (no_of_bytes>>8 & 0xFF)
        rxSize_2 = (no_of_bytes>>16 & 0xFF)
        rxSize_3 = (no_of_bytes>>24 & 0xFF)
        bReserved = 0x00

        #last two bytes are termination chars not supported by the rigol and must be 0
        frame = [MsgID, self.bTag, bTagInverse, bReserved, rxSize_0, rxSize_1, \
         rxSize_2, rxSize_3, 0x00, 0x00]

        # pad the frame to 4 byte (32bit) chunks
        while ((len(frame) % 4) > 0):
        	frame += [0x00]

        ret = self.__dev.write(0x02, frame)

        """
        Try and read the response back from the device
        """
        ret = self.__dev.read(0x86, no_of_bytes + 13, 0, timeout_ms)

        return ret

    def trim_response(self, response):
        _response = response
        data_byte_count = _response[4]+(_response[5]<<8)+\
        (_response[6]<<16)+(_response[7]<<24)

        #remove the header section
        for x in range(0,12):
            del _response[0]

        #remove all padding from the end
        while len(_response) > data_byte_count:
            del _response[-1]

        return _response

    def close(self):
        #reset the usb bus
        self.__dev.reset()