#Labjack streaming by Rohan Lele
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global STREAM_OUT0_BUFFER_SIZE_BYTES
STREAM_OUT0_BUFFER_SIZE_BYTES = 512

global STREAM_OUT0_LOOP_SIZE
STREAM_OUT0_LOOP_SIZE = 128

global SLEEP_TIME
SLEEP_TIME = 1/(STREAM_OUT0_LOOP_SIZE-1)

#This is the address of stream out0 buffer(4800)
global STREAM_OUT0
STREAM_OUT0 = 4800


def setupStream(LJHandle):

    #Get the address of DAC0 channel
    #nameToAddress is a function which takes string input of device name
    #and outputs a list with address and type of the device.
    #Here address is first element of list and type is second.
    target = ljm.nameToAddress("DAC0")[0]

    # Allocate memory for the stream-out buffer
    #eWriteName - This function will write a value to the device register
    try:
        #Disable stream_out0_enable by writing 0 to it, in case it was already enabled
        ljm.eWriteName(LJHandle, "STREAM_OUT0_ENABLE", 0)
        
        #Write the address of DAC0 to stream_out0_target
        ljm.eWriteName(LJHandle,"STREAM_OUT0_TARGET",target)

        #Write the value of stream_out0_buffer_size (512 in this case)
        ljm.eWriteName(LJHandle, "STREAM_OUT0_BUFFER_SIZE", STREAM_OUT0_BUFFER_SIZE_BYTES)
    
        #Enable stream_out0_enable by writing 1 to it
        ljm.eWriteName(LJHandle, "STREAM_OUT0_ENABLE", 1)
        
    except ljm.LJMError:
        print "\nFunction setupStream\n",sys.exc_info()[1]
        return


###################################################################

#Arguments:
    #LJHandle - Handle of opened labjack device
    #vdc_scan_rate - Rate at which samples are needed to be streamed
    #streamOutList - list of samples to be streamed
    
def startStream(LJHandle,vdc_scan_rate,streamOutList):

    SCAN_LIST = [STREAM_OUT0] 

    #Write the loop size 128 to the stream out loop size.
    ljm.eWriteName(LJHandle, "STREAM_OUT0_LOOP_SIZE", STREAM_OUT0_LOOP_SIZE)

    # Configure and start stream
    #1 - number of addresses in scanList(here only one as DAC0)
    #SCAN_LIST - list of all the addresses to where data is to be streamed. Here only one DAC0
    scan_rate = ljm.eStreamStart(LJHandle, vdc_scan_rate, 1, SCAN_LIST, vdc_scan_rate)
    
    #Write the first set of 128 values to the out buffer since i=0
    i=0

    try:    

        while 1:
            #Get the stream out0 buffer status
            bs = ljm.eReadName(LJHandle, "STREAM_OUT0_BUFFER_STATUS")

            #If the buffer status is greater than half the buffer size
            if bs >= STREAM_OUT0_LOOP_SIZE:
                 
                #Write the next 128 values into the buffer
                #-------------------------------------------------------------
                #Write the values in the buffer - This is NOT working. Please explain.
                #ljm.eWriteNameArray(LJHandle, "STREAM_OUT0_BUFFER_F32", STREAM_OUT0_LOOP_SIZE, streamOutList[i:i+STREAM_OUT0_LOOP_SIZE])
                
                #Write the values in the buffer and 
                for sampleValue in streamOutList[i:i+STREAM_OUT0_LOOP_SIZE]:
                    ljm.eWriteName(LJHandle, "STREAM_OUT0_BUFFER_F32", sampleValue)
            
                #Set the stream out loop to 1
                ljm.eWriteName(LJHandle, "STREAM_OUT0_SET_LOOP", 1)
                #-------------------------------------------------------------

                i=i+STREAM_OUT0_LOOP_SIZE

            #If sample values are over, break and exit
            if len(streamOutList[i:i+STREAM_OUT0_LOOP_SIZE])== 0:           
                break

            #Wait for buffer to empty before checking again
            time.sleep(SLEEP_TIME)
        
    except ljm.LJMError:
        print "\tFunction startStream\n",sys.exc_info()[1]

        exc_type, exc_obj, exc_tb = sys.exc_info()
        fname = os.path.split(exc_tb.tb_frame.f_code.co_filename)[1]
        print(exc_type, fname, exc_tb.tb_lineno)
        return

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