diff --git a/artiq/coredevice/i2c.py b/artiq/coredevice/i2c.py
index b51a6add2..8fbe56ceb 100644
--- a/artiq/coredevice/i2c.py
+++ b/artiq/coredevice/i2c.py
@@ -30,6 +30,9 @@ def i2c_read(busno: TInt32, ack: TBool) -> TInt32:
 class PCA9548:
     """Driver for the PCA9548 I2C bus switch.
 
+    I2C transactions not real-time, and are performed by the CPU without
+    involving RTIO.
+
     On the KC705, this chip is used for selecting the I2C buses on the two FMC
     connectors. HPC=1, LPC=2.
     """
@@ -72,6 +75,9 @@ class PCA9548:
 class TCA6424A:
     """Driver for the TCA6424A I2C I/O expander.
 
+    I2C transactions not real-time, and are performed by the CPU without
+    involving RTIO.
+
     On the NIST QC2 hardware, this chip is used for switching the directions
     of TTL buffers."""
     def __init__(self, dmgr, busno=0, address=0x44, core_device="core"):
diff --git a/artiq/coredevice/spi.py b/artiq/coredevice/spi.py
index 6c4b3e7ea..3b1129604 100644
--- a/artiq/coredevice/spi.py
+++ b/artiq/coredevice/spi.py
@@ -1,10 +1,20 @@
 import numpy
 
-from artiq.language.core import kernel, portable, now_mu, delay_mu
+from artiq.language.core import syscall, kernel, portable, now_mu, delay_mu
+from artiq.language.types import TInt32, TNone
 from artiq.language.units import MHz
 from artiq.coredevice.rtio import rtio_output, rtio_input_data
 
 
+__all__ = [
+  "SPI_DATA_ADDR", "SPI_XFER_ADDR", "SPI_CONFIG_ADDR",
+  "SPI_OFFLINE", "SPI_ACTIVE", "SPI_PENDING",
+  "SPI_CS_POLARITY", "SPI_CLK_POLARITY", "SPI_CLK_PHASE",
+  "SPI_LSB_FIRST", "SPI_HALF_DUPLEX",
+  "SPIMaster", "NRTSPIMaster"
+]
+
+
 SPI_DATA_ADDR, SPI_XFER_ADDR, SPI_CONFIG_ADDR = range(3)
 (
     SPI_OFFLINE,
@@ -262,3 +272,65 @@ class SPIMaster:
         rtio_output(now_mu(), self.channel, SPI_CONFIG_ADDR | SPI_RT2WB_READ,
                     0)
         return rtio_input_data(self.channel)
+
+
+@syscall(flags={"nounwind", "nowrite"})
+def spi_set_config(busno: TInt32, flags: TInt32, write_div: TInt32, read_div: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
+@syscall(flags={"nounwind", "nowrite"})
+def spi_set_xfer(busno: TInt32, chip_select: TInt32, write_length: TInt32, read_length: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
+@syscall(flags={"nounwind", "nowrite"})
+def spi_write(busno: TInt32, data: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
+@syscall(flags={"nounwind", "nowrite"})
+def spi_read(busno: TInt32) -> TInt32:
+    raise NotImplementedError("syscall not simulated")
+
+
+class NRTSPIMaster:
+    """Core device non-realtime Serial Peripheral Interface (SPI) bus master.
+    Owns one non-realtime SPI bus.
+
+    With this driver, SPI transactions and are performed by the CPU without
+    involving RTIO.
+
+    Realtime and non-realtime buses are separate and defined at bitstream
+    compilation time.
+
+    See :class:`SPIMaster` for a description of the methods.
+    """
+    def __init__(self, dmgr, busno, core_device="core"):
+        self.core = dmgr.get(core_device)
+        self.busno = busno
+
+    @kernel
+    def set_config_mu(self, flags=0, write_div=6, read_div=6):
+        """Set the ``config`` register.
+
+        Note that the non-realtime SPI cores are usually clocked by the system
+        clock and not the RTIO clock. In many cases, the SPI configuration is
+        already set by the firmware and you do not need to call this method.
+
+        The offline bit cannot be set using this method.
+        The SPI bus is briefly taken offline when this method is called.
+        """
+        spi_set_config(self.busno, flags, write_div, read_div)
+
+    @kernel
+    def set_xfer(self, chip_select=0, write_length=0, read_length=0):
+        spi_set_xfer(self.busno, chip_select, write_length, read_length)
+
+    @kernel
+    def write(self, data=0):
+        spi_write(self.busno, data)
+
+    @kernel
+    def read(self):
+        return spi_read(self.busno)
diff --git a/artiq/firmware/ksupport/api.rs b/artiq/firmware/ksupport/api.rs
index efb458f68..792f92f52 100644
--- a/artiq/firmware/ksupport/api.rs
+++ b/artiq/firmware/ksupport/api.rs
@@ -117,8 +117,13 @@ static mut API: &'static [(&'static str, *const ())] = &[
     api!(drtio_get_packet_counts = ::rtio::drtio_dbg::get_packet_counts),
     api!(drtio_get_fifo_space_req_count = ::rtio::drtio_dbg::get_fifo_space_req_count),
 
-    api!(i2c_start = ::i2c_start),
-    api!(i2c_stop = ::i2c_stop),
-    api!(i2c_write = ::i2c_write),
-    api!(i2c_read = ::i2c_read),
+    api!(i2c_start = ::nrt_bus::i2c::start),
+    api!(i2c_stop = ::nrt_bus::i2c::stop),
+    api!(i2c_write = ::nrt_bus::i2c::write),
+    api!(i2c_read = ::nrt_bus::i2c::read),
+
+    api!(spi_set_config = ::nrt_bus::spi::set_config),
+    api!(spi_set_xfer = ::nrt_bus::spi::set_xfer),
+    api!(spi_write = ::nrt_bus::spi::write),
+    api!(spi_read = ::nrt_bus::spi::read),
 ];
diff --git a/artiq/firmware/ksupport/lib.rs b/artiq/firmware/ksupport/lib.rs
index 0fd8c9f9b..2f06b0118 100644
--- a/artiq/firmware/ksupport/lib.rs
+++ b/artiq/firmware/ksupport/lib.rs
@@ -89,6 +89,7 @@ macro_rules! raise {
 pub mod eh;
 mod api;
 mod rtio;
+mod nrt_bus;
 
 static mut NOW: u64 = 0;
 static mut LIBRARY: Option<Library<'static>> = None;
@@ -220,24 +221,6 @@ extern fn cache_put(key: CSlice<u8>, list: CSlice<i32>) {
     })
 }
 
-extern fn i2c_start(busno: i32) {
-    send(&I2cStartRequest { busno: busno as u8 });
-}
-
-extern fn i2c_stop(busno: i32) {
-    send(&I2cStopRequest { busno: busno as u8 });
-}
-
-extern fn i2c_write(busno: i32, data: i32) -> bool {
-    send(&I2cWriteRequest { busno: busno as u8, data: data as u8 });
-    recv!(&I2cWriteReply { ack } => ack)
-}
-
-extern fn i2c_read(busno: i32, ack: bool) -> i32 {
-    send(&I2cReadRequest { busno: busno as u8, ack: ack });
-    recv!(&I2cReadReply { data } => data) as i32
-}
-
 const DMA_BUFFER_SIZE: usize = 64 * 1024;
 
 struct DmaRecorder {
diff --git a/artiq/firmware/ksupport/nrt_bus.rs b/artiq/firmware/ksupport/nrt_bus.rs
new file mode 100644
index 000000000..1f05f189b
--- /dev/null
+++ b/artiq/firmware/ksupport/nrt_bus.rs
@@ -0,0 +1,48 @@
+pub mod i2c {
+    use ::send;
+    use ::recv;
+    use kernel_proto::*;
+
+    pub extern fn start(busno: i32) {
+        send(&I2cStartRequest { busno: busno as u8 });
+    }
+
+    pub extern fn stop(busno: i32) {
+        send(&I2cStopRequest { busno: busno as u8 });
+    }
+
+    pub extern fn write(busno: i32, data: i32) -> bool {
+        send(&I2cWriteRequest { busno: busno as u8, data: data as u8 });
+        recv!(&I2cWriteReply { ack } => ack)
+    }
+
+    pub extern fn read(busno: i32, ack: bool) -> i32 {
+        send(&I2cReadRequest { busno: busno as u8, ack: ack });
+        recv!(&I2cReadReply { data } => data) as i32
+    }
+}
+
+pub mod spi {
+    use ::send;
+    use ::recv;
+    use kernel_proto::*;
+
+    pub extern fn set_config(busno: i32, flags: i32, write_div: i32, read_div: i32) {
+        send(&SpiSetConfigRequest { busno: busno as u32, flags: flags as u8,
+                                    write_div: write_div as u8, read_div: read_div as u8 });
+    }
+
+    pub extern fn set_xfer(busno: i32, chip_select: i32, write_length: i32, read_length: i32) {
+        send(&SpiSetXferRequest { busno: busno as u32, chip_select: chip_select as u16,
+                                  write_length: write_length as u8, read_length: read_length as u8 });
+    }
+
+    pub extern fn write(busno: i32, data: i32) {
+        send(&SpiWriteRequest { busno: busno as u32, data: data as u32 });
+    }
+
+    pub extern fn read(busno: i32) -> i32 {
+        send(&SpiReadRequest { busno: busno as u32 });
+        recv!(&SpiReadReply { data } => data) as i32
+    }
+}
diff --git a/artiq/firmware/libboard/i2c.rs b/artiq/firmware/libboard/i2c.rs
index 6a2fb61c8..4f9c6b7b3 100644
--- a/artiq/firmware/libboard/i2c.rs
+++ b/artiq/firmware/libboard/i2c.rs
@@ -1,147 +1,171 @@
 use csr;
-use clock;
 
-fn half_period() { clock::spin_us(100) }
-fn sda_bit(busno: u8) -> u8 { 1 << (2 * busno + 1) }
-fn scl_bit(busno: u8) -> u8 { 1 << (2 * busno) }
+#[cfg(has_i2c)]
+mod io {
+    use csr;
+    use clock;
 
-fn sda_i(busno: u8) -> bool {
-    unsafe {
-        csr::i2c::in_read() & sda_bit(busno) != 0
-    }
-}
-
-fn sda_oe(busno: u8, oe: bool) {
-    unsafe {
-        let reg = csr::i2c::oe_read();
-        let reg = if oe { reg | sda_bit(busno) } else { reg & !sda_bit(busno) };
-        csr::i2c::oe_write(reg)
-    }
-}
-
-fn sda_o(busno: u8, o: bool) {
-    unsafe {
-        let reg = csr::i2c::out_read();
-        let reg = if o  { reg | sda_bit(busno) } else { reg & !sda_bit(busno) };
-        csr::i2c::out_write(reg)
-    }
-}
-
-fn scl_oe(busno: u8, oe: bool) {
-    unsafe {
-        let reg = csr::i2c::oe_read();
-        let reg = if oe { reg | scl_bit(busno) } else { reg & !scl_bit(busno) };
-        csr::i2c::oe_write(reg)
-    }
-}
-
-fn scl_o(busno: u8, o: bool) {
-    unsafe {
-        let reg = csr::i2c::out_read();
-        let reg = if o  { reg | scl_bit(busno) } else { reg & !scl_bit(busno) };
-        csr::i2c::out_write(reg)
+    pub fn half_period() { clock::spin_us(100) }
+    fn sda_bit(busno: u8) -> u8 { 1 << (2 * busno + 1) }
+    fn scl_bit(busno: u8) -> u8 { 1 << (2 * busno) }
+
+    pub fn sda_i(busno: u8) -> bool {
+        unsafe {
+            csr::i2c::in_read() & sda_bit(busno) != 0
+        }
+    }
+
+    pub fn sda_oe(busno: u8, oe: bool) {
+        unsafe {
+            let reg = csr::i2c::oe_read();
+            let reg = if oe { reg | sda_bit(busno) } else { reg & !sda_bit(busno) };
+            csr::i2c::oe_write(reg)
+        }
+    }
+
+    pub fn sda_o(busno: u8, o: bool) {
+        unsafe {
+            let reg = csr::i2c::out_read();
+            let reg = if o  { reg | sda_bit(busno) } else { reg & !sda_bit(busno) };
+            csr::i2c::out_write(reg)
+        }
+    }
+
+    pub fn scl_oe(busno: u8, oe: bool) {
+        unsafe {
+            let reg = csr::i2c::oe_read();
+            let reg = if oe { reg | scl_bit(busno) } else { reg & !scl_bit(busno) };
+            csr::i2c::oe_write(reg)
+        }
+    }
+
+    pub fn scl_o(busno: u8, o: bool) {
+        unsafe {
+            let reg = csr::i2c::out_read();
+            let reg = if o  { reg | scl_bit(busno) } else { reg & !scl_bit(busno) };
+            csr::i2c::out_write(reg)
+        }
     }
 }
 
+#[cfg(has_i2c)]
 pub fn init() {
     for busno in 0..csr::CONFIG_I2C_BUS_COUNT {
         let busno = busno as u8;
         // Set SCL as output, and high level
-        scl_o(busno, true);
-        scl_oe(busno, true);
+        io::scl_o(busno, true);
+        io::scl_oe(busno, true);
         // Prepare a zero level on SDA so that sda_oe pulls it down
-        sda_o(busno, false);
+        io::sda_o(busno, false);
         // Release SDA
-        sda_oe(busno, false);
+        io::sda_oe(busno, false);
 
         // Check the I2C bus is ready
-        half_period();
-        half_period();
-        if !sda_i(busno) {
+        io::half_period();
+        io::half_period();
+        if !io::sda_i(busno) {
             error!("SDA is stuck low on bus #{}", busno)
         }
     }
 }
 
+#[cfg(has_i2c)]
 pub fn start(busno: u8) {
     // Set SCL high then SDA low
-    scl_o(busno, true);
-    half_period();
-    sda_oe(busno, true);
-    half_period();
+    io::scl_o(busno, true);
+    io::half_period();
+    io::sda_oe(busno, true);
+    io::half_period();
 }
 
+#[cfg(has_i2c)]
 pub fn restart(busno: u8) {
     // Set SCL low then SDA high */
-    scl_o(busno, false);
-    half_period();
-    sda_oe(busno, false);
-    half_period();
+    io::scl_o(busno, false);
+    io::half_period();
+    io::sda_oe(busno, false);
+    io::half_period();
     // Do a regular start
     start(busno);
 }
 
+#[cfg(has_i2c)]
 pub fn stop(busno: u8) {
     // First, make sure SCL is low, so that the target releases the SDA line
-    scl_o(busno, false);
-    half_period();
+    io::scl_o(busno, false);
+    io::half_period();
     // Set SCL high then SDA high
-    sda_oe(busno, true);
-    scl_o(busno, true);
-    half_period();
-    sda_oe(busno, false);
-    half_period();
+    io::sda_oe(busno, true);
+    io::scl_o(busno, true);
+    io::half_period();
+    io::sda_oe(busno, false);
+    io::half_period();
 }
 
+#[cfg(has_i2c)]
 pub fn write(busno: u8, data: u8) -> bool {
     // MSB first
     for bit in (0..8).rev() {
         // Set SCL low and set our bit on SDA
-        scl_o(busno, false);
-        sda_oe(busno, data & (1 << bit) == 0);
-        half_period();
+        io::scl_o(busno, false);
+        io::sda_oe(busno, data & (1 << bit) == 0);
+        io::half_period();
         // Set SCL high ; data is shifted on the rising edge of SCL
-        scl_o(busno, true);
-        half_period();
+        io::scl_o(busno, true);
+        io::half_period();
     }
     // Check ack
     // Set SCL low, then release SDA so that the I2C target can respond
-    scl_o(busno, false);
-    half_period();
-    sda_oe(busno, false);
+    io::scl_o(busno, false);
+    io::half_period();
+    io::sda_oe(busno, false);
     // Set SCL high and check for ack
-    scl_o(busno, true);
-    half_period();
+    io::scl_o(busno, true);
+    io::half_period();
     // returns true if acked (I2C target pulled SDA low)
-    !sda_i(busno)
+    !io::sda_i(busno)
 }
 
+#[cfg(has_i2c)]
 pub fn read(busno: u8, ack: bool) -> u8 {
     // Set SCL low first, otherwise setting SDA as input may cause a transition
     // on SDA with SCL high which will be interpreted as START/STOP condition.
-    scl_o(busno, false);
-    half_period(); // make sure SCL has settled low
-    sda_oe(busno, false);
+    io::scl_o(busno, false);
+    io::half_period(); // make sure SCL has settled low
+    io::sda_oe(busno, false);
 
     let mut data: u8 = 0;
 
     // MSB first
     for bit in (0..8).rev() {
-        scl_o(busno, false);
-        half_period();
+        io::scl_o(busno, false);
+        io::half_period();
         // Set SCL high and shift data
-        scl_o(busno, true);
-        half_period();
-        if sda_i(busno) { data |= 1 << bit }
+        io::scl_o(busno, true);
+        io::half_period();
+        if io::sda_i(busno) { data |= 1 << bit }
     }
     // Send ack
     // Set SCL low and pull SDA low when acking
-    scl_o(busno, false);
-    if ack { sda_oe(busno, true) }
-    half_period();
+    io::scl_o(busno, false);
+    if ack { io::sda_oe(busno, true) }
+    io::half_period();
     // then set SCL high
-    scl_o(busno, true);
-    half_period();
+    io::scl_o(busno, true);
+    io::half_period();
 
     data
 }
+
+#[cfg(not(has_i2c))]
+pub fn init() {}
+#[cfg(not(has_i2c))]
+pub fn start(_busno: u8) {}
+#[cfg(not(has_i2c))]
+pub fn restart(_busno: u8) {}
+#[cfg(not(has_i2c))]
+pub fn stop(_busno: u8) {}
+#[cfg(not(has_i2c))]
+pub fn write(_busno: u8, _data: u8) -> bool { false }
+#[cfg(not(has_i2c))]
+pub fn read(_busno: u8, _ack: bool) { 0xff }
diff --git a/artiq/firmware/libboard/lib.rs b/artiq/firmware/libboard/lib.rs
index 3c1f3cac8..d0c6ecc77 100644
--- a/artiq/firmware/libboard/lib.rs
+++ b/artiq/firmware/libboard/lib.rs
@@ -19,8 +19,9 @@ pub mod uart_console;
 #[cfg(has_spiflash)]
 pub mod spiflash;
 
-#[cfg(has_i2c)]
 pub mod i2c;
+pub mod spi;
+
 #[cfg(has_si5324)]
 pub mod si5324;
 
diff --git a/artiq/firmware/libboard/spi.rs b/artiq/firmware/libboard/spi.rs
new file mode 100644
index 000000000..afacb652a
--- /dev/null
+++ b/artiq/firmware/libboard/spi.rs
@@ -0,0 +1,54 @@
+#[cfg(has_converter_spi)]
+use csr;
+
+// Later this module should support other buses than the converter SPI bus,
+// and add a busno parameter to differentiate them.
+
+#[cfg(has_converter_spi)]
+pub fn set_config(flags: u8, write_div: u8, read_div: u8) {
+    unsafe {
+        csr::converter_spi::offline_write(1);
+        csr::converter_spi::cs_polarity_write(flags >> 3 & 1);
+        csr::converter_spi::clk_polarity_write(flags >> 4 & 1);
+        csr::converter_spi::clk_phase_write(flags >> 5 & 1);
+        csr::converter_spi::lsb_first_write(flags >> 6 & 1);
+        csr::converter_spi::half_duplex_write(flags >> 7 & 1);
+        csr::converter_spi::clk_div_write_write(write_div);
+        csr::converter_spi::clk_div_read_write(read_div);
+        csr::converter_spi::offline_write(0);
+    }
+}
+
+#[cfg(has_converter_spi)]
+pub fn set_xfer(chip_select: u16, write_length: u8, read_length: u8) {
+    unsafe {
+        csr::converter_spi::cs_write(chip_select as _);
+        csr::converter_spi::xfer_len_write_write(write_length);
+        csr::converter_spi::xfer_len_read_write(read_length);
+    }
+}
+
+#[cfg(has_converter_spi)]
+pub fn write(data: u32) {
+    unsafe {
+        csr::converter_spi::data_write_write(data);
+        while csr::converter_spi::pending_read() != 0 {}
+        while csr::converter_spi::active_read() != 0 {}
+    }
+}
+
+#[cfg(has_converter_spi)]
+pub fn read() -> u32 {
+    unsafe {
+        csr::converter_spi::data_read_read()
+    }
+}
+
+#[cfg(not(has_converter_spi))]
+pub fn set_config(_flags: u8, _write_div: u8, _read_div: u8) {}
+#[cfg(not(has_converter_spi))]
+pub fn set_xfer(_chip_select: u16, _write_length: u8, _read_length: u8) {}
+#[cfg(not(has_converter_spi))]
+pub fn write(_data: u32) {}
+#[cfg(not(has_converter_spi))]
+pub fn read() -> u32 { 0 }
diff --git a/artiq/firmware/libproto/kernel_proto.rs b/artiq/firmware/libproto/kernel_proto.rs
index 8688e534a..22fd38a18 100644
--- a/artiq/firmware/libproto/kernel_proto.rs
+++ b/artiq/firmware/libproto/kernel_proto.rs
@@ -87,6 +87,12 @@ pub enum Message<'a> {
     I2cReadRequest { busno: u8, ack: bool },
     I2cReadReply { data: u8 },
 
+    SpiSetConfigRequest { busno: u32, flags: u8, write_div: u8, read_div: u8 },
+    SpiSetXferRequest { busno: u32, chip_select: u16, write_length: u8, read_length: u8 },
+    SpiWriteRequest { busno: u32, data: u32 },
+    SpiReadRequest { busno: u32 },
+    SpiReadReply { data: u32 },
+
     Log(fmt::Arguments<'a>),
     LogSlice(&'a str)
 }
diff --git a/artiq/firmware/runtime/kern_hwreq.rs b/artiq/firmware/runtime/kern_hwreq.rs
new file mode 100644
index 000000000..ca21b5ed7
--- /dev/null
+++ b/artiq/firmware/runtime/kern_hwreq.rs
@@ -0,0 +1,123 @@
+use session::{kern_acknowledge, kern_send};
+use rtio_mgt;
+use board;
+use kernel_proto as kern;
+use std::io;
+use sched::Io;
+
+// TODO
+mod drtio_spi {
+    pub fn set_config(_busno: u32, _flags: u8, _write_div: u8, _read_div: u8) {}
+    pub fn set_xfer(_busno: u32, _chip_select: u16, _write_length: u8, _read_length: u8) {}
+    pub fn write(_busno: u32, _data: u32) {}
+    pub fn read(_busno: u32) -> u32 { 0 }
+}
+
+mod spi {
+    use board;
+    use super::drtio_spi;
+
+    pub fn set_config(busno: u32, flags: u8, write_div: u8, read_div: u8) {
+        let drtio = busno >> 16;
+        if drtio == 0 {
+            board::spi::set_config(flags, write_div, read_div)
+        } else {
+            drtio_spi::set_config(busno, flags, write_div, read_div)
+        }
+    }
+
+    pub fn set_xfer(busno: u32, chip_select: u16, write_length: u8, read_length: u8) {
+        let drtio = busno >> 16;
+        if drtio == 0 {
+            board::spi::set_xfer(chip_select, write_length, read_length)
+        } else {
+            drtio_spi::set_xfer(busno, chip_select, write_length, read_length)
+        }
+    }
+
+    pub fn write(busno: u32, data: u32) {
+        let drtio = busno >> 16;
+        if drtio == 0 {
+            board::spi::write(data)
+        } else {
+            drtio_spi::write(busno, data)
+        }
+    }
+
+    pub fn read(busno: u32) -> u32 {
+        let drtio = busno >> 16;
+        if drtio == 0 {
+            board::spi::read()
+        } else {
+            drtio_spi::read(busno)
+        }
+    }
+}
+
+pub fn process_kern_hwreq(io: &Io, request: &kern::Message) -> io::Result<bool> {
+    match request {
+        &kern::RtioInitRequest => {
+            info!("resetting RTIO");
+            rtio_mgt::init_core();
+            kern_acknowledge()
+        }
+
+        &kern::DrtioChannelStateRequest { channel } => {
+            let (fifo_space, last_timestamp) = rtio_mgt::drtio_dbg::get_channel_state(channel);
+            kern_send(io, &kern::DrtioChannelStateReply { fifo_space: fifo_space,
+                                                          last_timestamp: last_timestamp })
+        }
+        &kern::DrtioResetChannelStateRequest { channel } => {
+            rtio_mgt::drtio_dbg::reset_channel_state(channel);
+            kern_acknowledge()
+        }
+        &kern::DrtioGetFifoSpaceRequest { channel } => {
+            rtio_mgt::drtio_dbg::get_fifo_space(channel);
+            kern_acknowledge()
+        }
+        &kern::DrtioPacketCountRequest => {
+            let (tx_cnt, rx_cnt) = rtio_mgt::drtio_dbg::get_packet_counts();
+            kern_send(io, &kern::DrtioPacketCountReply { tx_cnt: tx_cnt, rx_cnt: rx_cnt })
+        }
+        &kern::DrtioFifoSpaceReqCountRequest => {
+            let cnt = rtio_mgt::drtio_dbg::get_fifo_space_req_count();
+            kern_send(io, &kern::DrtioFifoSpaceReqCountReply { cnt: cnt })
+        }
+
+        &kern::I2cStartRequest { busno } => {
+            board::i2c::start(busno);
+            kern_acknowledge()
+        }
+        &kern::I2cStopRequest { busno } => {
+            board::i2c::stop(busno);
+            kern_acknowledge()
+        }
+        &kern::I2cWriteRequest { busno, data } => {
+            let ack = board::i2c::write(busno, data);
+            kern_send(io, &kern::I2cWriteReply { ack: ack })
+        }
+        &kern::I2cReadRequest { busno, ack } => {
+            let data = board::i2c::read(busno, ack);
+            kern_send(io, &kern::I2cReadReply { data: data })
+        },
+
+        &kern::SpiSetConfigRequest { busno, flags, write_div, read_div } => {
+            spi::set_config(busno, flags, write_div, read_div);
+            kern_acknowledge()
+        },
+        &kern::SpiSetXferRequest { busno, chip_select, write_length, read_length } => {
+            spi::set_xfer(busno, chip_select, write_length, read_length);
+            kern_acknowledge()
+        }
+        &kern::SpiWriteRequest { busno, data } => {
+            spi::write(busno, data);
+            kern_acknowledge()
+        }
+        &kern::SpiReadRequest { busno } => {
+            let data = spi::read(busno);
+            kern_send(io, &kern::SpiReadReply { data: data })
+        },
+
+        _ => return Ok(false)
+    }.and(Ok(true))
+}
diff --git a/artiq/firmware/runtime/lib.rs b/artiq/firmware/runtime/lib.rs
index f5a7a16b5..c9cc36315 100644
--- a/artiq/firmware/runtime/lib.rs
+++ b/artiq/firmware/runtime/lib.rs
@@ -47,6 +47,7 @@ mod rtio_dma;
 
 mod mgmt;
 mod kernel;
+mod kern_hwreq;
 mod session;
 #[cfg(any(has_rtio_moninj, has_drtio))]
 mod moninj;
diff --git a/artiq/firmware/runtime/session.rs b/artiq/firmware/runtime/session.rs
index b1bbf49d0..9feb59d0b 100644
--- a/artiq/firmware/runtime/session.rs
+++ b/artiq/firmware/runtime/session.rs
@@ -15,6 +15,7 @@ use board;
 use rpc_proto as rpc;
 use session_proto as host;
 use kernel_proto as kern;
+use kern_hwreq;
 
 macro_rules! unexpected {
     ($($arg:tt)*) => {
@@ -125,7 +126,7 @@ fn host_write(stream: &mut Write, reply: host::Reply) -> io::Result<()> {
     reply.write_to(stream)
 }
 
-fn kern_send(io: &Io, request: &kern::Message) -> io::Result<()> {
+pub fn kern_send(io: &Io, request: &kern::Message) -> io::Result<()> {
     match request {
         &kern::LoadRequest(_) => debug!("comm->kern LoadRequest(...)"),
         &kern::DmaRetrieveReply { trace, duration } => {
@@ -176,7 +177,7 @@ fn kern_recv<R, F>(io: &Io, f: F) -> io::Result<R>
     })
 }
 
-fn kern_acknowledge() -> io::Result<()> {
+pub fn kern_acknowledge() -> io::Result<()> {
     mailbox::acknowledge();
     Ok(())
 }
@@ -364,6 +365,9 @@ fn process_kern_message(io: &Io, mut stream: Option<&mut TcpStream>,
         }
 
         kern_recv_dotrace(request);
+        if kern_hwreq::process_kern_hwreq(io, request)? {
+            return Ok(false)
+        }
         match request {
             &kern::Log(args) => {
                 use std::fmt::Write;
@@ -387,12 +391,6 @@ fn process_kern_message(io: &Io, mut stream: Option<&mut TcpStream>,
                 kern_acknowledge()
             }
 
-            &kern::RtioInitRequest => {
-                info!("resetting RTIO");
-                rtio_mgt::init_core();
-                kern_acknowledge()
-            }
-
             &kern::DmaRecordStart(name) => {
                 session.congress.dma_manager.record_start(name);
                 kern_acknowledge()
@@ -419,28 +417,6 @@ fn process_kern_message(io: &Io, mut stream: Option<&mut TcpStream>,
                 })
             }
 
-            &kern::DrtioChannelStateRequest { channel } => {
-                let (fifo_space, last_timestamp) = rtio_mgt::drtio_dbg::get_channel_state(channel);
-                kern_send(io, &kern::DrtioChannelStateReply { fifo_space: fifo_space,
-                                                                  last_timestamp: last_timestamp })
-            }
-            &kern::DrtioResetChannelStateRequest { channel } => {
-                rtio_mgt::drtio_dbg::reset_channel_state(channel);
-                kern_acknowledge()
-            }
-            &kern::DrtioGetFifoSpaceRequest { channel } => {
-                rtio_mgt::drtio_dbg::get_fifo_space(channel);
-                kern_acknowledge()
-            }
-            &kern::DrtioPacketCountRequest => {
-                let (tx_cnt, rx_cnt) = rtio_mgt::drtio_dbg::get_packet_counts();
-                kern_send(io, &kern::DrtioPacketCountReply { tx_cnt: tx_cnt, rx_cnt: rx_cnt })
-            }
-            &kern::DrtioFifoSpaceReqCountRequest => {
-                let cnt = rtio_mgt::drtio_dbg::get_fifo_space_req_count();
-                kern_send(io, &kern::DrtioFifoSpaceReqCountReply { cnt: cnt })
-            }
-
             &kern::WatchdogSetRequest { ms } => {
                 let id = session.watchdog_set.set_ms(ms)
                                 .map_err(|()| io_error("out of watchdogs"))?;
@@ -478,44 +454,6 @@ fn process_kern_message(io: &Io, mut stream: Option<&mut TcpStream>,
                 kern_send(io, &kern::CachePutReply { succeeded: succeeded })
             }
 
-            #[cfg(has_i2c)]
-            &kern::I2cStartRequest { busno } => {
-                board::i2c::start(busno);
-                kern_acknowledge()
-            }
-            #[cfg(has_i2c)]
-            &kern::I2cStopRequest { busno } => {
-                board::i2c::stop(busno);
-                kern_acknowledge()
-            }
-            #[cfg(has_i2c)]
-            &kern::I2cWriteRequest { busno, data } => {
-                let ack = board::i2c::write(busno, data);
-                kern_send(io, &kern::I2cWriteReply { ack: ack })
-            }
-            #[cfg(has_i2c)]
-            &kern::I2cReadRequest { busno, ack } => {
-                let data = board::i2c::read(busno, ack);
-                kern_send(io, &kern::I2cReadReply { data: data })
-            }
-
-            #[cfg(not(has_i2c))]
-            &kern::I2cStartRequest { .. } => {
-                kern_acknowledge()
-            }
-            #[cfg(not(has_i2c))]
-            &kern::I2cStopRequest { .. } => {
-                kern_acknowledge()
-            }
-            #[cfg(not(has_i2c))]
-            &kern::I2cWriteRequest { .. } => {
-                kern_send(io, &kern::I2cWriteReply { ack: false })
-            }
-            #[cfg(not(has_i2c))]
-            &kern::I2cReadRequest { .. } => {
-                kern_send(io, &kern::I2cReadReply { data: 0xff })
-            }
-
             &kern::RunFinished => {
                 unsafe { kernel::stop() }
                 session.kernel_state = KernelState::Absent;