diff --git a/charon_vna/vna.py b/charon_vna/vna.py
index 5513fc1..ff48d08 100644
--- a/charon_vna/vna.py
+++ b/charon_vna/vna.py
@@ -1,7 +1,7 @@
 # %% imports
 import copy
 from pathlib import Path
-from typing import Optional
+from typing import Any, Dict, Optional
 
 import adi
 import iio
@@ -17,99 +17,128 @@ from util import HAM_BANDS, db20, net2s, s2net
 dir_ = Path(__file__).parent
 
 
-# https://wiki.analog.com/resources/tools-software/linux-drivers/iio-transceiver/ad9361-customization
-
-
-# %% helper functions
-def get_config(sdr: adi.ad9361):
-    config = dict()
-    config["rx_lo"] = sdr.rx_lo
-    config["rx_rf_bandwidth"] = sdr.rx_rf_bandwidth
-    config["rx_enabled_channels"] = sdr.rx_enabled_channels
-    for chan in config["rx_enabled_channels"]:
-        config[f"rx_hardwaregain_chan{chan}"] = getattr(sdr, f"rx_hardwaregain_chan{chan}")
-        config[f"gain_control_mode_chan{chan}"] = getattr(sdr, f"gain_control_mode_chan{chan}")
-
-    config["tx_lo"] = sdr.tx_lo
-    config["tx_rf_bandwidth"] = sdr.tx_rf_bandwidth
-    config["tx_cyclic_buffer"] = sdr.tx_cyclic_buffer
-    config["tx_enabled_channels"] = sdr.tx_enabled_channels
-    for chan in config["tx_enabled_channels"]:
-        config[f"tx_hardwaregain_chan{chan}"] = getattr(sdr, f"tx_hardwaregain_chan{chan}")
-
-    config["filter"] = sdr.filter
-    config["sample_rate"] = sdr.sample_rate
-    config["loopback"] = sdr.loopback
-
-    return config
-
-
-def generate_tone(f: float, N: int = 1024, fs: Optional[float] = None):
-    if fs is None:
-        fs = sdr.sample_rate
-    fs = int(fs)
-    fc = int(f / (fs / N)) * (fs / N)
-    ts = 1 / float(fs)
-    t = np.arange(0, N * ts, ts)
-    i = np.cos(2 * np.pi * t * fc) * 2**14
-    q = np.sin(2 * np.pi * t * fc) * 2**14
-    iq = i + 1j * q
-
-    return iq
-
-
 # %% connection
-sdr = adi.ad9361(uri="ip:192.168.3.1")
+class Charon:
+    def __init__(
+        self,
+        uri: str,
+        frequency: npt.ArrayLike = np.linspace(1e9, 2e9, 3),
+    ):
+        # everything RF
+        self.sdr = adi.ad9361(uri=uri)
+        for attr, expected in [
+            ("adi,2rx-2tx-mode-enable", True),
+            ("adi,gpo-manual-mode-enable", True),
+        ]:
+            # available configuration options:
+            # https://wiki.analog.com/resources/tools-software/linux-drivers/iio-transceiver/ad9361-customization
+            if bool(self.sdr._get_iio_debug_attr(attr)) != expected:
+                raise ValueError(
+                    f"'{attr}' is not set in pluto. "
+                    "See README.md for instructions for one time configuration instructions"
+                )
+                # TODO: it might be possible to change this on the fly.
+                # I think we'll actually just fail in __init__ of ad9361 if 2rx-2tx is wrong
 
-# %% verify device configuration
-mode_2r2t = bool(sdr._get_iio_debug_attr("adi,2rx-2tx-mode-enable"))
-if not mode_2r2t:
-    raise ValueError("'adi,2rx-2tx-mode-enable' is not set in pluto. See README.md for instructions for changing this")
-# TODO: it might be possible to change this on the fly. I think we'll actually just fail in __init__ for sdr
+        self.sdr.rx_lo = int(frequency[0])
+        self.sdr.tx_lo = int(frequency[0])
+        self.sdr.sample_rate = 30e6
+        self.sdr.rx_rf_bandwidth = int(4e6)
+        self.sdr.tx_rf_bandwidth = int(4e6)
+        self.sdr.rx_destroy_buffer()
+        self.sdr.tx_destroy_buffer()
+        self.sdr.rx_enabled_channels = [0, 1]
+        self.sdr.tx_enabled_channels = [0]
+        self.sdr.loopback = 0
+        self.sdr.gain_control_mode_chan0 = "manual"
+        self.sdr.gain_control_mode_chan1 = "manual"
+        self.sdr.rx_hardwaregain_chan0 = 40
+        self.sdr.rx_hardwaregain_chan1 = 40
+        self.sdr.tx_hardwaregain_chan0 = -10
 
-# %% switch control outputs
-# NOTE: this doesn't appear to work
-sdr._set_iio_debug_attr_str("adi,gpo-manual-mode-enable", "1")
-sdr._get_iio_debug_attr_str("adi,gpo-manual-mode-enable-mask")
-# but direct register access does
-# https://ez.analog.com/linux-software-drivers/f/q-a/120853/control-fmcomms3-s-gpo-with-python
-ctx = iio.Context("ip:192.168.3.1")
-ctrl = ctx.find_device("ad9361-phy")
-# https://www.analog.com/media/cn/technical-documentation/user-guides/ad9364_register_map_reference_manual_ug-672.pdf
-ctrl.reg_write(0x26, 0x90)  # bit 7: AuxDAC Manual, bit 4: GPO Manual
-ctrl.reg_write(0x27, 0x10)  # bits 7-4: GPO3-0
+        # switch control
+        ctx = iio.Context(uri)
+        self.ctrl = ctx.find_device("ad9361-phy")
+        # raw ad9361 register accesss:
+        # https://ez.analog.com/linux-software-drivers/f/q-a/120853/control-fmcomms3-s-gpo-with-python
+        # https://www.analog.com/media/cn/technical-documentation/user-guides/ad9364_register_map_reference_manual_ug-672.pdf
+        self.ctrl.reg_write(0x26, 0x90)  # bit 7: AuxDAC Manual, bit 4: GPO Manual
+        self._set_gpo(0)
+        # TODO: init AuxDAC
+
+    def get_config(self) -> Dict[str, Any]:
+        config = dict()
+        config["rx_lo"] = self.sdr.rx_lo
+        config["rx_rf_bandwidth"] = self.sdr.rx_rf_bandwidth
+        config["rx_enabled_channels"] = self.sdr.rx_enabled_channels
+        for chan in config["rx_enabled_channels"]:
+            config[f"rx_hardwaregain_chan{chan}"] = getattr(self.sdr, f"rx_hardwaregain_chan{chan}")
+            config[f"gain_control_mode_chan{chan}"] = getattr(self.sdr, f"gain_control_mode_chan{chan}")
+
+        config["tx_lo"] = self.sdr.tx_lo
+        config["tx_rf_bandwidth"] = self.sdr.tx_rf_bandwidth
+        config["tx_cyclic_buffer"] = self.sdr.tx_cyclic_buffer
+        config["tx_enabled_channels"] = self.sdr.tx_enabled_channels
+        for chan in config["tx_enabled_channels"]:
+            config[f"tx_hardwaregain_chan{chan}"] = getattr(self.sdr, f"tx_hardwaregain_chan{chan}")
+
+        config["filter"] = self.sdr.filter
+        config["sample_rate"] = self.sdr.sample_rate
+        config["loopback"] = self.sdr.loopback
+
+        return config
+
+    def _set_gpo(self, value: int) -> None:
+        self.ctrl.reg_write(0x27, (value & 0x0F) << 4)  # bits 7-4: GPO3-0
+
+    def set_output_power(self, power: float):
+        if power == -5:
+            # FIXME: this is a hack because I don't want to go through re-calibration
+            tx_gain = -8
+        else:
+            raise NotImplementedError()
+            # # TODO: correct over frequency
+            # tx_gain_idx = np.abs(pout.sel(tx_channel=0) - power).argmin(dim="tx_gain")
+            # tx_gain = pout.coords["tx_gain"][tx_gain_idx]
+        self.sdr.tx_hardwaregain_chan0 = float(tx_gain)
+
+    def set_output(self, frequency: float, power: float, offset_frequency: float = 1e6):
+        # TODO: switch to DDS in Pluto
+        def generate_tone(f: float, N: int = 1024, fs: Optional[float] = None):
+            if fs is None:
+                fs = sdr.sample_rate
+            fs = int(fs)
+            fc = int(f / (fs / N)) * (fs / N)
+            ts = 1 / float(fs)
+            t = np.arange(0, N * ts, ts)
+            i = np.cos(2 * np.pi * t * fc) * 2**14
+            q = np.sin(2 * np.pi * t * fc) * 2**14
+            iq = i + 1j * q
+
+            return iq
+
+        self.sdr.tx_destroy_buffer()
+        self.set_output_power(power)
+        self.sdr.tx_lo = int(frequency - offset_frequency)
+        offset_frequency = frequency - self.sdr.tx_lo
+        self.sdr.tx_cyclic_buffer = True
+        self.sdr.tx(generate_tone(offset_frequency))
+
+    def _rx(self) -> npt.ArrayLike:
+        self.sdr.rx_destroy_buffer()
+        return np.array(self.sdr.rx())
+
+
+# %%
+sdr = Charon("ip:192.168.3.1")
 
 
 # %% initialization
-sdr.rx_lo = int(2.0e9)
-sdr.tx_lo = int(2.0e9)
-sdr.sample_rate = 30e6
-sdr.rx_rf_bandwidth = int(4e6)
-sdr.tx_rf_bandwidth = int(4e6)
-sdr.rx_destroy_buffer()
-sdr.tx_destroy_buffer()
-sdr.rx_enabled_channels = [0, 1]
-sdr.tx_enabled_channels = [0]
-sdr.loopback = 0
-sdr.gain_control_mode_chan0 = "manual"
-sdr.gain_control_mode_chan1 = "manual"
-sdr.rx_hardwaregain_chan0 = 40
-sdr.rx_hardwaregain_chan1 = 40
-sdr.tx_hardwaregain_chan0 = -10
-
-config = get_config(sdr)
+config = sdr.get_config()
 config
 
-# %%
-sdr.tx_destroy_buffer()  # must destroy buffer before changing cyclicity
-sdr.tx_cyclic_buffer = True
-sdr.tx(generate_tone(1e6))
-
-# %%
-sdr.rx_destroy_buffer()
-data = sdr.rx()
-
 # %% Plot in time
+data = sdr._rx()
 fig, axs = plt.subplots(2, 1, sharex=True, tight_layout=True)
 axs[0].plot(np.real(data).T)
 axs[1].plot(np.imag(data).T)
@@ -131,28 +160,6 @@ plt.grid(True)
 plt.show()
 
 
-# %% TX helper functions
-def set_output_power(power: float):
-    if power == -5:
-        # FIXME: this is a hack because I don't want to go through re-calibration
-        tx_gain = -8
-    else:
-        raise NotImplementedError()
-        # # TODO: correct over frequency
-        # tx_gain_idx = np.abs(pout.sel(tx_channel=0) - power).argmin(dim="tx_gain")
-        # tx_gain = pout.coords["tx_gain"][tx_gain_idx]
-    sdr.tx_hardwaregain_chan0 = float(tx_gain)
-
-
-def set_output(frequency: float, power: float, offset_frequency: float = 1e6):
-    sdr.tx_destroy_buffer()
-    set_output_power(power)
-    sdr.tx_lo = int(frequency - offset_frequency)
-    offset_frequency = frequency - sdr.tx_lo
-    sdr.tx_cyclic_buffer = True
-    sdr.tx(generate_tone(offset_frequency))
-
-
 # %%
 def vna_capture(frequency: npt.ArrayLike):
     s = xr.DataArray(