diff --git a/src/lvmopstools/devices/ion.py b/src/lvmopstools/devices/ion.py
index 3d52973..e5f7d18 100644
--- a/src/lvmopstools/devices/ion.py
+++ b/src/lvmopstools/devices/ion.py
@@ -11,7 +11,7 @@
 import asyncio
 import warnings
 
-from typing import TypedDict
+from typing import TypedDict, cast
 
 from drift import Drift
 from drift.convert import data_to_float32
@@ -61,10 +61,12 @@ async def _read_one_ion_controller(ion_config: dict) -> dict[str, IonPumpDict]:
             signal_address = camera_config["signal_address"]
             # on_off_address = camera_config["on_off_address"]
 
-            signal = await drift.client.read_input_registers(signal_address, 2)
-            # onoff = await drift.client.read_input_registers(on_off_address, 1)
+            signal = await drift.client.read_input_registers(signal_address, count=2)
+            # onoff = await drift.client.read_input_registers(on_off_address, count=1)
 
-            diff_volt = data_to_float32(tuple(signal.registers))
+            registers = cast(tuple[int, int], tuple(signal.registers))
+
+            diff_volt = data_to_float32(registers)
             pressure = convert_pressure(diff_volt)
 
             # onoff_status = bool(onoff.registers[0])
diff --git a/tests/test_devices.py b/tests/test_devices.py
index 4e45a1b..46e233d 100644
--- a/tests/test_devices.py
+++ b/tests/test_devices.py
@@ -88,13 +88,16 @@ async def test_toggle_ion_pump(ion_pump_server):
     on_off_address = b2_config["on_off_address"]
 
     async with drift:
-        register_z2 = await drift.client.read_holding_registers(on_off_address, 1)
+        register_z2 = await drift.client.read_holding_registers(
+            on_off_address,
+            count=1,
+        )
         assert register_z2.registers[0] == 0
 
     await toggle_ion_pump("b2", True)
 
     async with drift:
-        register_z2 = await drift.client.read_holding_registers(0, 50)
+        register_z2 = await drift.client.read_holding_registers(0, count=50)
         assert sum([reg > 0 for reg in register_z2.registers]) == 1
 
 
@@ -106,5 +109,5 @@ async def test_toggle_ion_pump_all(ion_pump_server):
     await toggle_ion_pump(ALL, True)
 
     async with drift:
-        register_z2 = await drift.client.read_holding_registers(0, 50)
+        register_z2 = await drift.client.read_holding_registers(0, count=50)
         assert sum([reg > 0 for reg in register_z2.registers]) == 3