diff --git a/ecp5/io.cc b/ecp5/io.cc
new file mode 100644
index 00000000..e86c84f6
--- /dev/null
+++ b/ecp5/io.cc
@@ -0,0 +1,217 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  David Shah <david@symbioticeda.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "io.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+std::string iovoltage_to_str(IOVoltage v)
+{
+    switch (v) {
+    case IOVoltage::VCC_3V3:
+        return "3V3";
+    case IOVoltage::VCC_2V5:
+        return "2V5";
+    case IOVoltage::VCC_1V8:
+        return "1V8";
+    case IOVoltage::VCC_1V5:
+        return "1V5";
+    case IOVoltage::VCC_1V35:
+        return "1V35";
+    case IOVoltage::VCC_1V2:
+        return "1V2";
+    }
+    NPNR_ASSERT_FALSE("unknown IO voltage");
+}
+
+IOVoltage iovoltage_from_str(const std::string &name)
+{
+    if (name == "3V3")
+        return IOVoltage::VCC_3V3;
+    if (name == "2V5")
+        return IOVoltage::VCC_2V5;
+    if (name == "1V8")
+        return IOVoltage::VCC_1V8;
+    if (name == "1V5")
+        return IOVoltage::VCC_1V5;
+    if (name == "1V35")
+        return IOVoltage::VCC_1V35;
+    if (name == "1V2")
+        return IOVoltage::VCC_1V2;
+    NPNR_ASSERT_FALSE("unknown IO voltage");
+}
+
+std::string iotype_to_str(IOType type)
+{
+    if (type == IOType::TYPE_NONE)
+        return "NONE";
+#define X(t)                                                                                                           \
+    if (type == IOType::t)                                                                                             \
+        return #t;
+#include "iotypes.inc"
+#undef X
+    if (type == IOType::TYPE_UNKNOWN)
+        return "<unknown>";
+    NPNR_ASSERT_FALSE("unknown IO type");
+}
+
+IOType ioType_from_str(const std::string &name)
+{
+    if (name == "NONE")
+        return IOType::TYPE_NONE;
+#define X(t)                                                                                                           \
+    if (name == #t)                                                                                                    \
+        return IOType::t;
+#include "iotypes.inc"
+    return IOType::TYPE_UNKNOWN;
+}
+
+IOVoltage get_vccio(IOType type)
+{
+    switch (type) {
+    case IOType::LVTTL33:
+    case IOType::LVCMOS33:
+    case IOType::LVCMOS33D:
+    case IOType::LVPECL33:
+    case IOType::LVPECL33E:
+        return IOVoltage::VCC_3V3;
+    case IOType::LVCMOS25:
+    case IOType::LVCMOS25D:
+    case IOType::LVDS:
+    case IOType::SLVS:
+    case IOType::SUBLVDS:
+    case IOType::LVDS25E:
+    case IOType::MLVDS25:
+    case IOType::MLVDS25E:
+    case IOType::BLVDS25:
+        return IOVoltage::VCC_2V5;
+    case IOType::LVCMOS18:
+    case IOType::LVCMOS18D:
+    case IOType::SSTL18_I:
+    case IOType::SSTL18_II:
+    case IOType::SSTL18D_I:
+    case IOType::SSTL18D_II:
+        return IOVoltage::VCC_1V8;
+    case IOType::LVCMOS15:
+    case IOType::SSTL15_I:
+    case IOType::SSTL15_II:
+    case IOType::SSTL15D_I:
+    case IOType::SSTL15D_II:
+        return IOVoltage::VCC_1V5;
+    case IOType::SSTL135_I:
+    case IOType::SSTL135_II:
+    case IOType::SSTL135D_I:
+    case IOType::SSTL135D_II:
+        return IOVoltage::VCC_1V35;
+    case IOType::LVCMOS12:
+    case IOType::HSUL12:
+    case IOType::HSUL12D:
+        return IOVoltage::VCC_1V2;
+    default:
+        NPNR_ASSERT_FALSE("unknown IO type, unable to determine VccIO");
+    }
+}
+
+bool is_strong_vccio_constraint(IOType type, PortType dir, IOSide side)
+{
+    if (dir == PORT_OUT || dir == PORT_INOUT)
+        return true;
+    switch (type) {
+    case IOType::TYPE_NONE:
+    case IOType::LVCMOS33D:
+    case IOType::LVPECL33:
+    case IOType::LVDS:
+    case IOType::MLVDS25:
+    case IOType::BLVDS25:
+    case IOType::SLVS:
+    case IOType::SUBLVDS:
+    case IOType::LVCMOS12:
+    case IOType::HSUL12:
+    case IOType::HSUL12D:
+        return false;
+    case IOType::LVCMOS33:
+    case IOType::LVTTL33:
+    case IOType::LVCMOS25:
+        return (side == IOSide::LEFT || side == IOSide::RIGHT);
+    default:
+        return true;
+    }
+}
+
+bool is_differential(IOType type)
+{
+    switch (type) {
+    case IOType::LVCMOS33D:
+    case IOType::LVCMOS25D:
+    case IOType::LVPECL33:
+    case IOType::LVDS:
+    case IOType::MLVDS25:
+    case IOType::BLVDS25:
+    case IOType::SLVS:
+    case IOType::SUBLVDS:
+    case IOType::LVCMOS18D:
+    case IOType::SSTL18D_I:
+    case IOType::SSTL18D_II:
+    case IOType::SSTL15D_I:
+    case IOType::SSTL15D_II:
+    case IOType::SSTL135D_I:
+    case IOType::SSTL135D_II:
+    case IOType::HSUL12D:
+        return true;
+    default:
+        return false;
+    }
+}
+
+bool is_referenced(IOType type)
+{
+    switch (type) {
+    case IOType::SSTL18_I:
+    case IOType::SSTL18_II:
+    case IOType::SSTL18D_I:
+    case IOType::SSTL18D_II:
+    case IOType::SSTL15_I:
+    case IOType::SSTL15_II:
+    case IOType::SSTL15D_I:
+    case IOType::SSTL15D_II:
+    case IOType::SSTL135_I:
+    case IOType::SSTL135_II:
+    case IOType::SSTL135D_I:
+    case IOType::SSTL135D_II:
+    case IOType::HSUL12:
+    case IOType::HSUL12D:
+        return true;
+    default:
+        return false;
+    }
+}
+
+bool valid_loc_for_io(IOType type, PortType dir, IOSide side, int z)
+{
+    bool is_lr = side == IOSide::LEFT || side == IOSide::RIGHT;
+    if (is_referenced(type) && !is_lr)
+        return false;
+    if (is_differential(type) && (!is_lr || ((z % 2) == 1)))
+        return false;
+    if ((type == IOType::LVCMOS18D || type == IOType::LVDS) && (dir == PORT_OUT || PORT_INOUT) && z != 0)
+        return false;
+    return true;
+}
+
+NEXTPNR_NAMESPACE_END
diff --git a/ecp5/io.h b/ecp5/io.h
new file mode 100644
index 00000000..f0d941d9
--- /dev/null
+++ b/ecp5/io.h
@@ -0,0 +1,70 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  David Shah <david@symbioticeda.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#ifndef IO_H
+#define IO_H
+
+#include "nextpnr.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+enum class IOVoltage
+{
+    VCC_3V3,
+    VCC_2V5,
+    VCC_1V8,
+    VCC_1V5,
+    VCC_1V35,
+    VCC_1V2
+};
+
+std::string iovoltage_to_str(IOVoltage v);
+IOVoltage iovoltage_from_str(const std::string &name);
+
+enum class IOType
+{
+    TYPE_NONE,
+#define X(t) t,
+#include "iotypes.inc"
+#undef X
+    TYPE_UNKNOWN,
+};
+
+enum class IOSide
+{
+    LEFT,
+    RIGHT,
+    TOP,
+    BOTTOM,
+};
+
+std::string iotype_to_str(IOType type);
+IOType ioType_from_str(const std::string &name);
+
+// IO related functions
+IOVoltage get_vccio(IOType type);
+bool is_strong_vccio_constraint(IOType type, PortType dir, IOSide side);
+bool is_differential(IOType type);
+bool is_referenced(IOType type);
+
+bool valid_loc_for_io(IOType type, PortType dir, IOSide side, int z);
+
+NEXTPNR_NAMESPACE_END
+
+#endif
diff --git a/ecp5/iotypes.inc b/ecp5/iotypes.inc
new file mode 100644
index 00000000..5984e79e
--- /dev/null
+++ b/ecp5/iotypes.inc
@@ -0,0 +1,37 @@
+X(LVTTL33)
+X(LVCMOS33)
+X(LVCMOS25)
+X(LVCMOS18)
+X(LVCMOS15)
+X(LVCMOS12)
+
+X(SSTL18_I)
+X(SSTL18_II)
+X(SSTL15_I)
+X(SSTL15_II)
+X(SSTL135_I)
+X(SSTL135_II)
+X(HSUL12)
+
+X(SSTL18D_I)
+X(SSTL18D_II)
+X(SSTL135D_I)
+X(SSTL135D_II)
+X(SSTL15D_I)
+X(SSTL15D_II)
+X(HSUL12D)
+X(LVCMOS33D)
+X(LVCMOS25D)
+
+X(LVDS)
+X(BLVDS25)
+X(MLVDS25)
+X(LVPECL33)
+X(SLVS)
+X(SUBLVDS)
+X(LVCMOS18D)
+
+X(LVDS25E)
+X(BLVDS25E)
+X(MLVDS25E)
+X(LVPECL33E)