diff --git a/board_config.zen b/board_config.zen
index 61fb497..f587956 100644
--- a/board_config.zen
+++ b/board_config.zen
@@ -351,7 +351,7 @@ BASE_2L_STACKUP = Stackup(
     materials=[FR4_CORE],
     thickness=1.6,
     symmetric=True,
-    copper_finish="HAL SnPb",
+    copper_finish="ENIG",
     silk_screen_color="White",
     solder_mask_color="Black",
     layers=[
@@ -376,7 +376,7 @@ BASE_4L_STACKUP = Stackup(
     materials=[FR4_CORE, BASE_PREPREG],
     thickness=1.6,
     symmetric=True,
-    copper_finish="HAL SnPb",
+    copper_finish="ENIG",
     silk_screen_color="White",
     solder_mask_color="Black",
     layers=[
@@ -458,7 +458,7 @@ BASE_6L_STACKUP = Stackup(
     ],
     thickness=1.6,
     symmetric=True,
-    copper_finish="HAL SnPb",
+    copper_finish="ENIG",
     silk_screen_color="White",
     solder_mask_color="Black",
     layers=[
@@ -546,7 +546,7 @@ BASE_8L_STACKUP = Stackup(
     ],
     thickness=1.6,
     symmetric=True,
-    copper_finish="HAL SnPb",
+    copper_finish="ENIG",
     silk_screen_color="White",
     solder_mask_color="Black",
     layers=[
diff --git a/interfaces.zen b/interfaces.zen
index 52cc791..852d071 100644
--- a/interfaces.zen
+++ b/interfaces.zen
@@ -1,4 +1,4 @@
-load("units.zen", "VoltageRange")
+load("units.zen", "VoltageRange", "Impedance")
 
 Power = builtin.net_type(
     "Power",
@@ -15,6 +15,12 @@ Analog = builtin.net_type("Analog")
 Pwm = builtin.net_type("Pwm")
 Gpio = builtin.net_type("Gpio")
 
+DiffPair = interface(
+    P=Net(),
+    N=Net(),
+    impedance=field(Impedance | None, default=None),
+)
+
 Can = interface(
     CAN_H=Net(),
     CAN_L=Net(),
@@ -26,116 +32,77 @@ CanTtl = interface(
 )
 
 Csi = interface(
-    CLK_P=Net(),
-    CLK_N=Net(),
-    D0_P=Net(),
-    D0_N=Net(),
-    D1_P=Net(),
-    D1_N=Net(),
-    D2_P=Net(),
-    D2_N=Net(),
-    D3_P=Net(),
-    D3_N=Net(),
-)
-
-DiffPair = interface(
-    P=Net("_P"),
-    N=Net("_N"),
+    CLK=DiffPair(impedance=Impedance(100)),
+    D0=DiffPair(impedance=Impedance(100)),
+    D1=DiffPair(impedance=Impedance(100)),
+    D2=DiffPair(impedance=Impedance(100)),
+    D3=DiffPair(impedance=Impedance(100)),
 )
 
 DisplayPort = interface(
-    AUX_P=Net(),
-    AUX_N=Net(),
-    ML0_P=Net(),
-    ML0_N=Net(),
-    ML1_P=Net(),
-    ML1_N=Net(),
-    ML2_P=Net(),
-    ML2_N=Net(),
-    ML3_P=Net(),
-    ML3_N=Net(),
+    AUX=DiffPair(impedance=Impedance(100)),
+    ML0=DiffPair(impedance=Impedance(100)),
+    ML1=DiffPair(impedance=Impedance(100)),
+    ML2=DiffPair(impedance=Impedance(100)),
+    ML3=DiffPair(impedance=Impedance(100)),
     HPD=Net(),
 )
 
 Dsi = interface(
-    CLK_P=Net(),
-    CLK_N=Net(),
-    D0_P=Net(),
-    D0_N=Net(),
-    D1_P=Net(),
-    D1_N=Net(),
-    D2_P=Net(),
-    D2_N=Net(),
-    D3_P=Net(),
-    D3_N=Net(),
+    CLK=DiffPair(impedance=Impedance(100)),
+    D0=DiffPair(impedance=Impedance(100)),
+    D1=DiffPair(impedance=Impedance(100)),
+    D2=DiffPair(impedance=Impedance(100)),
+    D3=DiffPair(impedance=Impedance(100)),
 )
 
 Edp = interface(
-    AUX_P=Net(),
-    AUX_N=Net(),
-    TX0_P=Net(),
-    TX0_N=Net(),
-    TX1_P=Net(),
-    TX1_N=Net(),
-    TX2_P=Net(),
-    TX2_N=Net(),
-    TX3_P=Net(),
-    TX3_N=Net(),
+    AUX=DiffPair(impedance=Impedance(100)),
+    TX0=DiffPair(impedance=Impedance(100)),
+    TX1=DiffPair(impedance=Impedance(100)),
+    TX2=DiffPair(impedance=Impedance(100)),
+    TX3=DiffPair(impedance=Impedance(100)),
 )
 
 Emmc = interface(
-    CLK=Net(),
-    CMD=Net(),
-    DAT0=Net(),
-    DAT1=Net(),
-    DAT2=Net(),
-    DAT3=Net(),
-    DAT4=Net(),
-    DAT5=Net(),
-    DAT6=Net(),
-    DAT7=Net(),
-    DS=Net(),
+    CLK=Net(impedance=Impedance(50)),
+    CMD=Net(impedance=Impedance(50)),
+    DAT0=Net(impedance=Impedance(50)),
+    DAT1=Net(impedance=Impedance(50)),
+    DAT2=Net(impedance=Impedance(50)),
+    DAT3=Net(impedance=Impedance(50)),
+    DAT4=Net(impedance=Impedance(50)),
+    DAT5=Net(impedance=Impedance(50)),
+    DAT6=Net(impedance=Impedance(50)),
+    DAT7=Net(impedance=Impedance(50)),
+    DS=Net(impedance=Impedance(50)),
     RST_N=Net(),
 )
 
 Ethernet = interface(
-    TX_P=Net(),
-    TX_N=Net(),
-    RX_P=Net(),
-    RX_N=Net(),
+    TX=DiffPair(impedance=Impedance(100)),
+    RX=DiffPair(impedance=Impedance(100)),
 )
 
 Ethernet_Phy = interface(
-    TR0_P=Net(),
-    TR0_N=Net(),
-    TR1_P=Net(),
-    TR1_N=Net(),
-    TR2_P=Net(),
-    TR2_N=Net(),
-    TR3_P=Net(),
-    TR3_N=Net(),
+    TR0=DiffPair(impedance=Impedance(100)),
+    TR1=DiffPair(impedance=Impedance(100)),
+    TR2=DiffPair(impedance=Impedance(100)),
+    TR3=DiffPair(impedance=Impedance(100)),
 )
 
 Ethernet_1000BaseT = interface(
-    BI_DA_P=Net(),
-    BI_DA_N=Net(),
-    BI_DB_P=Net(),
-    BI_DB_N=Net(),
-    BI_DC_P=Net(),
-    BI_DC_N=Net(),
-    BI_DD_P=Net(),
-    BI_DD_N=Net(),
+    BI_DA=DiffPair(impedance=Impedance(100)),
+    BI_DB=DiffPair(impedance=Impedance(100)),
+    BI_DC=DiffPair(impedance=Impedance(100)),
+    BI_DD=DiffPair(impedance=Impedance(100)),
 )
 
 Hdmi = interface(
-    CLK_P=Net(),
-    CLK_N=Net(),
-    D0_P=Net(),
-    D0_N=Net(),
-    D1_P=Net(),
-    D1_N=Net(),
-    D2_P=Net(),
-    D2_N=Net(),
+    CLK=DiffPair(impedance=Impedance(100)),
+    D0=DiffPair(impedance=Impedance(100)),
+    D1=DiffPair(impedance=Impedance(100)),
+    D2=DiffPair(impedance=Impedance(100)),
     CEC=Net(),
     SCL=Net(),
     SDA=Net(),
@@ -199,14 +166,10 @@ Lcd = interface(
 )
 
 Lvds = interface(
-    CLK_P=Net(),
-    CLK_N=Net(),
-    DATA0_P=Net(),
-    DATA0_N=Net(),
-    DATA1_P=Net(),
-    DATA1_N=Net(),
-    DATA2_P=Net(),
-    DATA2_N=Net(),
+    CLK=DiffPair(impedance=Impedance(100)),
+    DATA0=DiffPair(impedance=Impedance(100)),
+    DATA1=DiffPair(impedance=Impedance(100)),
+    DATA2=DiffPair(impedance=Impedance(100)),
 )
 
 Mdio = interface(
@@ -215,14 +178,10 @@ Mdio = interface(
 )
 
 Mdi = interface(
-    A_P=Net(),
-    A_N=Net(),
-    B_P=Net(),
-    B_N=Net(),
-    C_P=Net(),
-    C_N=Net(),
-    D_P=Net(),
-    D_N=Net(),
+    A=DiffPair(impedance=Impedance(100)),
+    B=DiffPair(impedance=Impedance(100)),
+    C=DiffPair(impedance=Impedance(100)),
+    D=DiffPair(impedance=Impedance(100)),
 )
 
 Mii = interface(
@@ -244,16 +203,11 @@ Mii = interface(
 )
 
 Mipi = interface(
-    CLK_P=Net(),
-    CLK_N=Net(),
-    DATA0_P=Net(),
-    DATA0_N=Net(),
-    DATA1_P=Net(),
-    DATA1_N=Net(),
-    DATA2_P=Net(),
-    DATA2_N=Net(),
-    DATA3_P=Net(),
-    DATA3_N=Net(),
+    CLK=DiffPair(impedance=Impedance(100)),
+    DATA0=DiffPair(impedance=Impedance(100)),
+    DATA1=DiffPair(impedance=Impedance(100)),
+    DATA2=DiffPair(impedance=Impedance(100)),
+    DATA3=DiffPair(impedance=Impedance(100)),
 )
 
 
@@ -277,81 +231,64 @@ OscPair = interface(
 )
 
 Pcie = interface(
-    TX_P=Net(),
-    TX_N=Net(),
-    RX_P=Net(),
-    RX_N=Net(),
-    REFCLK_P=Net(),
-    REFCLK_N=Net(),
+    TX=DiffPair(impedance=Impedance(85)),
+    RX=DiffPair(impedance=Impedance(85)),
+    REFCLK=DiffPair(impedance=Impedance(85)),
     PERST=Net(),
     WAKE=Net(),
 )
 
 PcieGen3x1Lane = interface(
-    TX_P=Net(),
-    TX_N=Net(),
-    RX_P=Net(),
-    RX_N=Net(),
-    REFCLK_P=Net(),
-    REFCLK_N=Net(),
+    TX=DiffPair(impedance=Impedance(85)),
+    RX=DiffPair(impedance=Impedance(85)),
+    REFCLK=DiffPair(impedance=Impedance(85)),
     RESET_N=Net(),
     WAKE_N=Net(),
     CLK_REQ_N=Net(),
 )
 
 PcieGen3x2Lane = interface(
-    TX0_P=Net(),
-    TX0_N=Net(),
-    RX0_P=Net(),
-    RX0_N=Net(),
-    TX1_P=Net(),
-    TX1_N=Net(),
-    RX1_P=Net(),
-    RX1_N=Net(),
-    REFCLK_P=Net(),
-    REFCLK_N=Net(),
+    TX0=DiffPair(impedance=Impedance(85)),
+    RX0=DiffPair(impedance=Impedance(85)),
+    TX1=DiffPair(impedance=Impedance(85)),
+    RX1=DiffPair(impedance=Impedance(85)),
+    REFCLK=DiffPair(impedance=Impedance(85)),
     RESET_N=Net(),
     WAKE_N=Net(),
     CLK_REQ_N=Net(),
 )
 
 QLink = interface(
-    CLK_P=Net(),
-    CLK_N=Net(),
-    L0_P=Net(),
-    L0_N=Net(),
-    L1_P=Net(),
-    L1_N=Net(),
-    L2_P=Net(),
-    L2_N=Net(),
-    L3_P=Net(),
-    L3_N=Net(),
-    L4_P=Net(),
-    L4_N=Net(),
+    CLK=DiffPair(impedance=Impedance(100)),
+    L0=DiffPair(impedance=Impedance(100)),
+    L1=DiffPair(impedance=Impedance(100)),
+    L2=DiffPair(impedance=Impedance(100)),
+    L3=DiffPair(impedance=Impedance(100)),
+    L4=DiffPair(impedance=Impedance(100)),
 )
 
 Qspi = interface(
-    CS=Net(),
-    CLK=Net(),
-    IO0=Net(),
-    IO1=Net(),
-    IO2=Net(),
-    IO3=Net(),
+    CS=Net(impedance=Impedance(50)),
+    CLK=Net(impedance=Impedance(50)),
+    IO0=Net(impedance=Impedance(50)),
+    IO1=Net(impedance=Impedance(50)),
+    IO2=Net(impedance=Impedance(50)),
+    IO3=Net(impedance=Impedance(50)),
 )
 
 Rgmii = interface(
-    TXD0=Net(),
-    TXD1=Net(),
-    TXD2=Net(),
-    TXD3=Net(),
-    TX_CTL=Net(),
-    TXC=Net(),
-    RXD0=Net(),
-    RXD1=Net(),
-    RXD2=Net(),
-    RXD3=Net(),
-    RX_CTL=Net(),
-    RXC=Net(),
+    TXD0=Net(impedance=Impedance(50)),
+    TXD1=Net(impedance=Impedance(50)),
+    TXD2=Net(impedance=Impedance(50)),
+    TXD3=Net(impedance=Impedance(50)),
+    TX_CTL=Net(impedance=Impedance(50)),
+    TXC=Net(impedance=Impedance(50)),
+    RXD0=Net(impedance=Impedance(50)),
+    RXD1=Net(impedance=Impedance(50)),
+    RXD2=Net(impedance=Impedance(50)),
+    RXD3=Net(impedance=Impedance(50)),
+    RX_CTL=Net(impedance=Impedance(50)),
+    RXC=Net(impedance=Impedance(50)),
 )
 
 Rmii = interface(
@@ -377,45 +314,39 @@ Rs232 = interface(
 )
 
 Rs422 = interface(
-    TX_P=Net("TX_P"),
-    TX_N=Net("TX_N"),
-    RX_P=Net("RX_P"),
-    RX_N=Net("RX_N"),
-    RTS_P=Net("RTS_P"),
-    RTS_N=Net("RTS_N"),
-    CTS_P=Net("CTS_P"),
-    CTS_N=Net("CTS_N"),
+    TX=DiffPair(impedance=Impedance(100)),
+    RX=DiffPair(impedance=Impedance(100)),
+    RTS=DiffPair(impedance=Impedance(100)),
+    CTS=DiffPair(impedance=Impedance(100)),
 )
 
 Rs485 = Rs422
 
 Sata = interface(
-    TX_P=Net(),
-    TX_N=Net(),
-    RX_P=Net(),
-    RX_N=Net(),
+    TX=DiffPair(impedance=Impedance(100)),
+    RX=DiffPair(impedance=Impedance(100)),
 )
 
 Sdio = interface(
-    CLK=Net(),
-    CMD=Net(),
-    DAT0=Net(),
-    DAT1=Net(),
-    DAT2=Net(),
-    DAT3=Net(),
+    CLK=Net(impedance=Impedance(50)),
+    CMD=Net(impedance=Impedance(50)),
+    DAT0=Net(impedance=Impedance(50)),
+    DAT1=Net(impedance=Impedance(50)),
+    DAT2=Net(impedance=Impedance(50)),
+    DAT3=Net(impedance=Impedance(50)),
 )
 
 Sdmmc = interface(
-    CLK=Net(),
-    CMD=Net(),
-    DAT0=Net(),
-    DAT1=Net(),
-    DAT2=Net(),
-    DAT3=Net(),
-    DAT4=Net(),
-    DAT5=Net(),
-    DAT6=Net(),
-    DAT7=Net(),
+    CLK=Net(impedance=Impedance(50)),
+    CMD=Net(impedance=Impedance(50)),
+    DAT0=Net(impedance=Impedance(50)),
+    DAT1=Net(impedance=Impedance(50)),
+    DAT2=Net(impedance=Impedance(50)),
+    DAT3=Net(impedance=Impedance(50)),
+    DAT4=Net(impedance=Impedance(50)),
+    DAT5=Net(impedance=Impedance(50)),
+    DAT6=Net(impedance=Impedance(50)),
+    DAT7=Net(impedance=Impedance(50)),
 )
 
 SmBus = I2c
@@ -468,41 +399,28 @@ def UsartPair(name_a: str, name_b: str) -> (Usart, Usart):
 Ufs = interface(
     REFCLK=Net(),
     RESET_N=Net(),
-    L0_RX_P=Net(),
-    L0_RX_N=Net(),
-    L0_TX_P=Net(),
-    L0_TX_N=Net(),
-    L1_RX_P=Net(),
-    L1_RX_N=Net(),
-    L1_TX_P=Net(),
-    L1_TX_N=Net(),
+    L0_RX=DiffPair(impedance=Impedance(100)),
+    L0_TX=DiffPair(impedance=Impedance(100)),
+    L1_RX=DiffPair(impedance=Impedance(100)),
+    L1_TX=DiffPair(impedance=Impedance(100)),
 )
 
 Usb2 = interface(
-    DP=Net("D_P"),
-    DM=Net("D_N"),
+    D=DiffPair(impedance=Impedance(90)),
 )
 
 Usb3 = interface(
-    DP=Net(),
-    DM=Net(),
-    SSTX_N=Net(),
-    SSTX_P=Net(),
-    SSRX_N=Net(),
-    SSRX_P=Net(),
+    D=DiffPair(impedance=Impedance(90)),
+    SSTX=DiffPair(impedance=Impedance(90)),
+    SSRX=DiffPair(impedance=Impedance(90)),
 )
 
 UsbTypeC = interface(
-    DP=Net("D_P"),
-    DM=Net("D_N"),
-    SSTX0_P=Net(),
-    SSTX0_N=Net(),
-    SSRX0_P=Net(),
-    SSRX0_N=Net(),
-    SSTX1_P=Net(),
-    SSTX1_N=Net(),
-    SSRX1_P=Net(),
-    SSRX1_N=Net(),
+    D=DiffPair(impedance=Impedance(90)),
+    SSTX0=DiffPair(impedance=Impedance(90)),
+    SSRX0=DiffPair(impedance=Impedance(90)),
+    SSTX1=DiffPair(impedance=Impedance(90)),
+    SSRX1=DiffPair(impedance=Impedance(90)),
     SBU1=Net(),
     SBU2=Net(),
     CC1=Net(),