diff --git a/src/gateware/aux_controller.py b/src/gateware/aux_controller.py
new file mode 100644
index 0000000..fc667b7
--- /dev/null
+++ b/src/gateware/aux_controller.py
@@ -0,0 +1,85 @@
+"""Auxiliary controller, common to satellite and master"""
+
+from artiq.gateware.drtio.aux_controller import Transmitter, Receiver
+from migen.fhdl.simplify import FullMemoryWE
+from misoc.interconnect.csr import *
+from migen_axi.interconnect.sram import SRAM
+from migen_axi.interconnect import axi
+
+max_packet = 1024
+
+class _DRTIOAuxControllerBase(Module):
+    def __init__(self, link_layer):
+        self.bus = axi.Interface()
+        self.submodules.transmitter = Transmitter(link_layer, len(self.bus.w.data))
+        self.submodules.receiver = Receiver(link_layer, len(self.bus.w.data))
+
+    def get_csrs(self):
+        return self.transmitter.get_csrs() + self.receiver.get_csrs()
+
+
+# TODO: FullMemoryWE should be applied by migen.build
+@FullMemoryWE()
+class DRTIOAuxControllerAxi(_DRTIOAuxControllerBase):
+    def __init__(self, link_layer):
+        _DRTIOAuxControllerBase.__init__(self, link_layer)
+
+        tx_sdram_if = SRAM(self.transmitter.mem, read_only=False)
+        rx_sdram_if = SRAM(self.receiver.mem, read_only=True)
+        aw_decoder = axi.AddressDecoder(self.bus.aw,
+            [(lambda a: a[log2_int(max_packet)] == 0, tx_sdram_if.bus.aw),
+             (lambda a: a[log2_int(max_packet)] == 1, rx_sdram_if.bus.aw)],
+            register=True)
+        ar_decoder = axi.AddressDecoder(self.bus.ar,
+            [(lambda a: a[log2_int(max_packet)] == 0, tx_sdram_if.bus.ar),
+             (lambda a: a[log2_int(max_packet)] == 1, rx_sdram_if.bus.ar)],
+            register=True)
+        # unlike wb, axi address decoder only connects ar/aw lanes,
+        # the rest must also be connected!
+        # not quite unlike an address decoder itself.
+
+        # connect bus.b with tx.b
+        self.comb += [tx_sdram_if.bus.b.ready.eq(self.bus.b.ready),
+                      self.bus.b.id.eq(tx_sdram_if.bus.b.id),
+                      self.bus.b.resp.eq(tx_sdram_if.bus.b.resp),
+                      self.bus.b.valid.eq(tx_sdram_if.bus.b.valid)]
+        # connect bus.w with tx.w
+        # no worries about w.valid and slave sel here, only tx will be written to
+        self.comb += [tx_sdram_if.bus.w.id.eq(self.bus.w.id),
+                      tx_sdram_if.bus.w.data.eq(self.bus.w.data),
+                      tx_sdram_if.bus.w.strb.eq(self.bus.w.strb),
+                      tx_sdram_if.bus.w.last.eq(self.bus.w.last),
+                      tx_sdram_if.bus.w.valid.eq(self.bus.w.valid),
+                      self.bus.w.ready.eq(tx_sdram_if.bus.w.ready)]
+        # connect bus.r with rx.r and tx.r w/o data
+        self.comb += [self.bus.r.id.eq(rx_sdram_if.bus.r.id | tx_sdram_if.bus.r.id),
+                #self.bus.r.data.eq(rx_sdram_if.bus.r.data | tx_sdram_if.bus.r.data),
+                self.bus.r.resp.eq(rx_sdram_if.bus.r.resp | tx_sdram_if.bus.r.resp),
+                self.bus.r.last.eq(rx_sdram_if.bus.r.last | tx_sdram_if.bus.r.last),
+                self.bus.r.valid.eq(rx_sdram_if.bus.r.valid | tx_sdram_if.bus.r.valid),
+                rx_sdram_if.bus.r.ready.eq(self.bus.r.ready),
+                tx_sdram_if.bus.r.ready.eq(self.bus.r.ready)]
+        # connect read data after being masked
+        masked = [Replicate(rx_sdram_if.bus.r.valid,
+                            len(self.bus.r.data)
+                            ) & rx_sdram_if.bus.r.data,
+                 Replicate(tx_sdram_if.bus.r.valid,
+                            len(self.bus.r.data)
+                            ) & tx_sdram_if.bus.r.data]
+        self.comb += self.bus.r.data.eq(reduce(or_, masked))
+
+        self.submodules += tx_sdram_if, rx_sdram_if, aw_decoder, ar_decoder
+
+
+@FullMemoryWE()
+class DRTIOAuxControllerBare(_DRTIOAuxControllerBase):
+    # Barebones version of the AuxController. No SRAM, no decoders.
+    # add memories manually from tx and rx in target code.
+    def get_tx_port(self):
+        return self.transmitter.mem.get_port(write_capable=True)
+
+    def get_rx_port(self):
+        return self.receiver.mem.get_port(write_capable=False)
+
+    def get_mem_size(self):
+        return max_packet