diff --git a/src/kaleidoscope/driver/sensor/ADNS5050.h b/src/kaleidoscope/driver/sensor/ADNS5050.h
new file mode 100644
index 00000000..aca99d01
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+++ b/src/kaleidoscope/driver/sensor/ADNS5050.h
@@ -0,0 +1,224 @@
+/* -*- mode: c++ -*-
+ * Kaleidoscope - Firmware for computer input devices
+ * Copyright (C) 2022  Keyboard.io, Inc
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#if defined(__AVR__)
+
+#include <stdint.h>  // for uint8_t
+#include "kaleidoscope/device/avr/pins_and_ports.h"
+
+namespace kaleidoscope {
+namespace driver {
+namespace sensor {
+
+struct ADNS5050BaseProps {
+  static constexpr uint8_t clock_pin = NO_PIN;
+  static constexpr uint8_t io_pin = NO_PIN;
+  static constexpr uint8_t chip_select_pin = NO_PIN;
+};
+
+template <typename _Props>
+class ADNS5050 {
+ public:
+  ADNS5050() {}
+
+  typedef struct Report {
+    int8_t dx;
+    int8_t dy;
+  };
+
+  enum class CPI {
+    CPI125 = 0x11,
+    CPI250 = 0x12,
+    CPI375 = 0x13,
+    CPI500 = 0x14,
+    CPI625 = 0x15,
+    CPI750 = 0x16,
+    CPI875 = 0x17,
+    CPI1000 = 0x18,
+    CPI1125 = 0x19,
+    CPI1250 = 0x1a,
+    CPI1375 = 0x1b
+  };
+
+  void setup() {
+    static_assert(_Props::clock_pin != NO_PIN, "No clock pin specified!");
+    static_assert(_Props::io_pin != NO_PIN, "No IO pin specified!");
+    static_assert(_Props::chip_select_pin != NO_PIN, "No chip select pin specified!");
+
+    DDR_OUTPUT(_Props::clock_pin);
+    DDR_OUTPUT(_Props::io_pin);
+    DDR_OUTPUT(_Props::chip_select_pin);
+
+    // 0x5a is chip reset (datasheet page 26)
+    writeRegister(Register::CHIP_RESET, 0x5a);
+    delay(55);
+
+    // read an initial report from the sensor, and discard it.
+    readReport();
+  }
+
+  void sync() {
+    cs_select();
+    delayMicroseconds(1);
+    cs_deselect();
+  }
+
+  Report readReport() {
+    Report report;
+
+    cs_select();
+
+    serialWrite(Register::MOTION_BURST);
+
+    uint8_t x = serialRead();
+    uint8_t y = serialRead();
+
+    cs_deselect();
+
+    report.dx = convertTwosComp(x);
+    report.dy = convertTwosComp(y);
+
+    return report;
+  }
+
+  void setCPI(CPI cpi) {
+    uint8_t cpival = cpi / 125;
+    if (cpival < 0x01) {
+      cpival = 0x1;
+    }
+    if (cpival > 0x0d) {
+      cpival = 0x0d;
+    }
+
+    writeRegister(Register::MOUSE_CONTROL2, 0b10000 | cpival);
+  }
+  CPI getCPI() {
+    // not implemented yet
+    return CPI::CPI125;
+  }
+
+  bool checkSignature() {
+    uint8_t rid = readRegister(Register::REVISION_ID);
+    uint8_t pid = readRegister(Register::PRODUCT_ID);
+    uint8_t pid2 = readRegister(Register::PRODUCT_ID2);
+
+    return (pid == 0x12 && rid == 0x01 && pid2 == 0x26);
+  }
+
+ public:
+  enum class Register {
+    PRODUCT_ID = 0x00,
+    REVISION_ID = 0x01,
+    MOTION = 0x02,
+    DELTA_X = 0x03,
+    DELTA_Y = 0x04,
+    MOUSE_CONTROL2 = 0x19,
+    CHIP_RESET = 0x3a,
+    PRODUCT_ID2 = 0x3e,
+    MOTION_BURST = 0x63
+  };
+
+  int8_t convertTwosComp(uint8_t data) {
+    if ((data & 0x80) == 0x80)
+      return -128 + (data & 0x7F);
+    else
+      return data;
+  }
+
+  uint8_t serialRead() {
+    DDR_INPUT(_Props::io_pin);
+    delayMicroseconds(1);
+
+    uint8_t byte;
+
+    for (uint8_t i = 0; i < 8; i++) {
+      OUTPUT_LOW(_Props::clock_pin);
+      delayMicroseconds(1);
+
+      byte = (byte  << 1) | READ_PIN(_Props::io_pin);
+
+      OUTPUT_HIGH(_Props::clock_pin);
+      delayMicroseconds(1);
+    }
+
+    return byte;
+  }
+
+  void serialWrite(uint8_t data) {
+    DDR_OUTPUT(_Props::io_pin);
+    delayMicroseconds(1);
+
+    for (int8_t i = 7; i >= 0; i--) {
+      OUTPUT_LOW(_Props::clock_pin);
+      delayMicroseconds(1);
+
+      if (data && (1 << i)) {
+        OUTPUT_HIGH(_Props::io_pin);
+      } else {
+        OUTPUT_LOW(_Props::io_pin);
+      }
+
+      delayMicroseconds(2);
+
+      OUTPUT_HIGH(_Props::clock_pin);
+      delayMicroseconds(1);
+    }
+
+    delayMicroseconds(4);
+  }
+  void serialWrite(Register reg) {
+    serialWrite((uint8_t) reg);
+  }
+
+  uint8_t readRegister(Register reg) {
+    cs_select();
+
+    serialWrite(reg);
+    uint8_t byte = serialRead();
+
+    delayMicroseconds(1);
+
+    cs_deselect();
+
+    return byte;
+  }
+  void writeRegister(Register reg, uint8_t data) {
+    cs_select();
+    serialWrite(0b10000000 | (uint8_t)reg);
+    serialWrite(data);
+    cs_deselect();
+  }
+
+  void cs_select() {
+    OUTPUT_LOW(_Props::chip_select_pin);
+    delayMicroseconds(1);
+  }
+  void cs_deselect() {
+    OUTPUT_HIGH(_Props::chip_select_pin);
+    delayMicroseconds(1);
+  }
+
+};
+
+}  // namespace sensor
+}  // namespace driver
+}  // namespace kaleidoscope
+
+#endif  // define(__AVR__)