diff --git a/src/finn/transformation/fpgadataflow/insert_iodma.py b/src/finn/transformation/fpgadataflow/insert_iodma.py
index ebd7cbe0276d3e9b4128275b0a65b1a9a40d1f80..27055a4fd29dba3849c0e4a889f27802f8c36081 100644
--- a/src/finn/transformation/fpgadataflow/insert_iodma.py
+++ b/src/finn/transformation/fpgadataflow/insert_iodma.py
@@ -33,7 +33,6 @@ from finn.util.basic import get_by_name
 from finn.custom_op.registry import getCustomOp
 from finn.transformation.base import Transformation
 from finn.transformation.general import SortGraph
-import finn.core.data_layout as DataLayout
 import math
 import numpy as np
 
@@ -59,6 +58,10 @@ class InsertIODMA(Transformation):
         addr = 1: [(pe-1,simd*2-1),.......(0,simd+1),(0,simd)]
         .
         """
+
+        # TODO: refactor this into streamingfclayer_batch.py, could go into
+        # make_weight_file except it doesn't write a file but returns a npy
+        # array instead
         w_shape = weights.shape
         assert len(w_shape) == 2, "weights withincorrect number of dims"
         inp_w, out_w = w_shape
@@ -70,13 +73,15 @@ class InsertIODMA(Transformation):
         addr = 0
         for fr in range(out_w // pe):
             for fc in range(inp_w // simd):
-                tile = weights[
-                    (fc * simd) : ((fc + 1) * simd), (fr * pe) : ((fr + 1) * pe)
-                ]
+                w0_lower = fc * simd
+                w0_upper = (fc + 1) * simd
+                w1_lower = fr * pe
+                w1_upper = (fr + 1) * pe
+                tile = weights[w0_lower:w0_upper, w1_lower:w1_upper]
                 for p in range(pe):
-                    reshaped_w[addr, (p * simd) : ((p + 1) * simd)] = tile[
-                        :, p
-                    ].transpose()
+                    rw0_lower = p * simd
+                    rw0_upper = (p + 1) * simd
+                    reshaped_w[addr, rw0_lower:rw0_upper] = tile[:, p].transpose()
                 addr += 1
         reshaped_w = np.flip(reshaped_w, axis=-1)
         return reshaped_w
@@ -92,8 +97,7 @@ class InsertIODMA(Transformation):
         fc_extw_nodes = list(
             filter(
                 lambda x: x.op_type == "StreamingFCLayer_Batch"
-                and get_by_name(x.attribute, "mem_mode") is not None
-                and get_by_name(x.attribute, "mem_mode").s.decode("UTF-8") == "external"
+                and getCustomOp(x).get_nodeattr("mem_mode") == "external"
                 and model.find_producer(x.input[1]) is None,
                 all_nodes,
             )
@@ -191,6 +195,7 @@ class InsertIODMA(Transformation):
                 )
                 model.graph.node.insert(0, dma_node)
             for fc_node in fc_extw_nodes:
+                fc_inst = getCustomOp(fc_node)
                 fc_w_name = fc_node.input[1]
                 w_shape = model.get_tensor_shape(fc_w_name)
                 w_dtype = model.get_tensor_datatype(fc_w_name)
@@ -203,7 +208,7 @@ class InsertIODMA(Transformation):
                 # calculate width of stream output from DMA
                 pe = get_by_name(fc_node.attribute, "PE").i
                 simd = get_by_name(fc_node.attribute, "SIMD").i
-                streamWidth = simd * pe * w_dtype.bitwidth()
+                streamWidth = fc_inst.get_weightstream_width_padded()
                 # make new buffer
                 W = model.get_initializer(fc_w_name)
                 iodma_mem = self.get_mem_init(W, pe, simd)