diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_Linux.cpp b/libraries/AP_OpticalFlow/AP_OpticalFlow_Linux.cpp
new file mode 100644
index 0000000000..2f426abdbe
--- /dev/null
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_Linux.cpp
@@ -0,0 +1,199 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+/*
+ 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 .
+ */
+
+/*
+ * AP_OpticalFlow_Linux.cpp - ardupilot library for the PX4Flow sensor.
+ * inspired by the PX4Firmware code.
+ *
+ * @author: Víctor Mayoral Vilches
+ *
+ */
+
+#include
+#include "OpticalFlow.h"
+
+#define DEBUG 1
+#define RAW_READ 0
+
+#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
+extern const AP_HAL::HAL& hal;
+
+AP_OpticalFlow_Linux::AP_OpticalFlow_Linux(OpticalFlow &_frontend) :
+ OpticalFlow_backend(_frontend)
+{}
+
+
+void AP_OpticalFlow_Linux::init(void)
+{
+ uint8_t buff[22];
+
+ // get pointer to i2c bus semaphore
+ AP_HAL::Semaphore *i2c_sem = hal.i2c->get_semaphore();
+
+ // take i2c bus sempahore
+ if (!i2c_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
+ hal.scheduler->panic(PSTR("PX4FLOW: unable to get semaphore"));
+ }
+
+ // to be sure this is not a ll40ls Lidar (which can also be on
+ // 0x42) we check if a I2C_FRAME_SIZE byte transfer works from address
+ // 0. The ll40ls gives an error for that, whereas the flow
+ // happily returns some data
+ uint8_t val[I2C_FRAME_SIZE];
+ if (hal.i2c->readRegisters(I2C_FLOW_ADDRESS, 0, I2C_FRAME_SIZE, val))
+ hal.scheduler->panic(PSTR("ll40ls Lidar"));
+
+ i2c_sem->give();
+
+}
+
+int AP_OpticalFlow_Linux::read(optical_flow_s* report)
+{
+ // get pointer to i2c bus semaphore
+ AP_HAL::Semaphore *i2c_sem = hal.i2c->get_semaphore();
+
+ // take i2c bus sempahore
+ if (!i2c_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
+ hal.scheduler->panic(PSTR("PX4FLOW: unable to get semaphore"));
+ }
+
+
+ uint8_t val[I2C_FRAME_SIZE + I2C_INTEGRAL_FRAME_SIZE] = { 0 };
+
+#if RAW_READ
+ hal.console->printf_P(PSTR("PX4FLOW: RAW_READ"));
+ // Send the command to begin a measurement
+ uint8_t cmd = PX4FLOW_REG;
+ if (hal.i2c->write(I2C_FLOW_ADDRESS, 1, &cmd)){
+ hal.console->printf_P(PSTR("PX4FLOW: Error while beginning a measurement"));
+ i2c_sem->give();
+ return 0;
+ }
+
+ // Perform the reading
+ if (PX4FLOW_REG == 0x00) {
+ if (hal.i2c->read(I2C_FLOW_ADDRESS, I2C_FRAME_SIZE + I2C_INTEGRAL_FRAME_SIZE, val)){
+ hal.console->printf_P(PSTR("PX4FLOW: Error while reading"));
+ i2c_sem->give();
+ return 0;
+ }
+ }
+
+ if (PX4FLOW_REG == 0x16) {
+ if (hal.i2c->read(I2C_FLOW_ADDRESS, I2C_INTEGRAL_FRAME_SIZE, val)){
+ hal.console->printf_P(PSTR("PX4FLOW: Error while reading"));
+ i2c_sem->give();
+ return 0;
+ }
+ }
+
+#else
+ // Perform the writing and reading in a single command
+ if (PX4FLOW_REG == 0x00) {
+ if (hal.i2c->readRegisters(I2C_FLOW_ADDRESS, PX4FLOW_REG, I2C_FRAME_SIZE + I2C_INTEGRAL_FRAME_SIZE, val)){
+ hal.console->printf_P(PSTR("PX4FLOW: Error while reading"));
+ i2c_sem->give();
+ return 0;
+ }
+ }
+
+ if (PX4FLOW_REG == 0x16) {
+ if (hal.i2c->readRegisters(I2C_FLOW_ADDRESS, PX4FLOW_REG, I2C_INTEGRAL_FRAME_SIZE, val)){
+ hal.console->printf_P(PSTR("PX4FLOW: Error while reading"));
+ i2c_sem->give();
+ return 0;
+ }
+ }
+#endif
+
+
+ if (PX4FLOW_REG == 0) {
+ memcpy(&f, val, I2C_FRAME_SIZE);
+ memcpy(&f_integral, &(val[I2C_FRAME_SIZE]), I2C_INTEGRAL_FRAME_SIZE);
+ }
+
+ if (PX4FLOW_REG == 0x16) {
+ memcpy(&f_integral, val, I2C_INTEGRAL_FRAME_SIZE);
+ }
+
+ // report->timestamp = hrt_absolute_time();
+ report->pixel_flow_x_integral = static_cast(f_integral.pixel_flow_x_integral) / 10000.0f;//convert to radians
+ report->pixel_flow_y_integral = static_cast(f_integral.pixel_flow_y_integral) / 10000.0f;//convert to radians
+ report->frame_count_since_last_readout = f_integral.frame_count_since_last_readout;
+ report->ground_distance_m = static_cast(f_integral.ground_distance) / 1000.0f;//convert to meters
+ report->quality = f_integral.qual; //0:bad ; 255 max quality
+ report->gyro_x_rate_integral = static_cast(f_integral.gyro_x_rate_integral) / 10000.0f; //convert to radians
+ report->gyro_y_rate_integral = static_cast(f_integral.gyro_y_rate_integral) / 10000.0f; //convert to radians
+ report->gyro_z_rate_integral = static_cast(f_integral.gyro_z_rate_integral) / 10000.0f; //convert to radians
+ report->integration_timespan = f_integral.integration_timespan; //microseconds
+ report->time_since_last_sonar_update = f_integral.sonar_timestamp;//microseconds
+ report->gyro_temperature = f_integral.gyro_temperature;//Temperature * 100 in centi-degrees Celsius
+
+ report->sensor_id = 0;
+
+ hal.console->printf_P(PSTR("PX4FLOW measurement: ground_distance_m: %f\n"), report->ground_distance_m);
+
+/*
+ // rotate measurements according to parameter
+ float zeroval = 0.0f;
+ rotate_3f(_sensor_rotation, report.pixel_flow_x_integral, report.pixel_flow_y_integral, zeroval);
+*/
+
+ i2c_sem->give();
+ return 1;
+
+}
+
+// update - read latest values from sensor and fill in x,y and totals.
+void AP_OpticalFlow_Linux::update(void)
+{
+ struct optical_flow_s report;
+
+ // read the report from the sensor
+ read(&report);
+
+ // process
+ struct OpticalFlow::OpticalFlow_state state;
+ state.device_id = report.sensor_id;
+ state.surface_quality = report.quality;
+ if (report.integration_timespan > 0) {
+ const Vector2f flowScaler = _flowScaler();
+ float flowScaleFactorX = 1.0f + 0.001f * flowScaler.x;
+ float flowScaleFactorY = 1.0f + 0.001f * flowScaler.y;
+ float integralToRate = 1e6f / float(report.integration_timespan);
+ state.flowRate.x = flowScaleFactorX * integralToRate * float(report.pixel_flow_x_integral); // rad/sec measured optically about the X sensor axis
+ state.flowRate.y = flowScaleFactorY * integralToRate * float(report.pixel_flow_y_integral); // rad/sec measured optically about the Y sensor axis
+ state.bodyRate.x = integralToRate * float(report.gyro_x_rate_integral); // rad/sec measured inertially about the X sensor axis
+ state.bodyRate.y = integralToRate * float(report.gyro_y_rate_integral); // rad/sec measured inertially about the Y sensor axis
+ } else {
+ state.flowRate.zero();
+ state.bodyRate.zero();
+ }
+
+#if DEBUG
+ hal.console->printf_P(PSTR("PX4FLOW print: sensor_id: %d\n"), state.device_id);
+ hal.console->printf_P(PSTR("PX4FLOW print: surface_quality: %d\n"), state.surface_quality);
+ hal.console->printf_P(PSTR("PX4FLOW print: flowRate.x: %d\n"), state.flowRate.x);
+ hal.console->printf_P(PSTR("PX4FLOW print: flowRate.y: %d\n"), state.flowRate.y);
+ hal.console->printf_P(PSTR("PX4FLOW print: bodyRate.x: %d\n"), state.bodyRate.x);
+ hal.console->printf_P(PSTR("PX4FLOW print: bodyRate.y: %d\n"), state.bodyRate.y);
+#endif
+ _update_frontend(state);
+}
+
+
+
+#endif // CONFIG_HAL_BOARD == HAL_BOARD_LINUX
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_Linux.h b/libraries/AP_OpticalFlow/AP_OpticalFlow_Linux.h
new file mode 100644
index 0000000000..a2fcbba562
--- /dev/null
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_Linux.h
@@ -0,0 +1,96 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+
+#ifndef AP_OpticalFlow_Linux_H
+#define AP_OpticalFlow_Linux_H
+
+#include "OpticalFlow.h"
+
+#include
+
+/* Configuration Constants */
+#define I2C_FLOW_ADDRESS 0x42 ///< 7-bit address. 8-bit address is 0x84, range 0x42 - 0x49
+
+/* PX4FLOW Registers addresses */
+#define PX4FLOW_REG 0x16 ///< Measure Register 22
+
+#define PX4FLOW_CONVERSION_INTERVAL 100000 ///< in microseconds! 20000 = 50 Hz 100000 = 10Hz
+#define PX4FLOW_I2C_MAX_BUS_SPEED 400000 ///< 400 KHz maximum speed
+
+typedef struct i2c_frame
+{
+ uint16_t frame_count;
+ int16_t pixel_flow_x_sum;
+ int16_t pixel_flow_y_sum;
+ int16_t flow_comp_m_x;
+ int16_t flow_comp_m_y;
+ int16_t qual;
+ int16_t gyro_x_rate;
+ int16_t gyro_y_rate;
+ int16_t gyro_z_rate;
+ uint8_t gyro_range;
+ uint8_t sonar_timestamp;
+ int16_t ground_distance;
+} i2c_frame;
+
+#define I2C_FRAME_SIZE (sizeof(i2c_frame))
+
+
+typedef struct i2c_integral_frame
+{
+ uint16_t frame_count_since_last_readout;
+ int16_t pixel_flow_x_integral;
+ int16_t pixel_flow_y_integral;
+ int16_t gyro_x_rate_integral;
+ int16_t gyro_y_rate_integral;
+ int16_t gyro_z_rate_integral;
+ uint32_t integration_timespan;
+ uint32_t sonar_timestamp;
+ uint16_t ground_distance;
+ int16_t gyro_temperature;
+ uint8_t qual;
+} i2c_integral_frame;
+
+#define I2C_INTEGRAL_FRAME_SIZE (sizeof(i2c_integral_frame))
+
+/**
+ * Optical flow in NED body frame in SI units.
+ *
+ * @see http://en.wikipedia.org/wiki/International_System_of_Units
+ */
+struct optical_flow_s {
+
+ uint64_t timestamp; /**< in microseconds since system start */
+ uint8_t sensor_id; /**< id of the sensor emitting the flow value */
+ float pixel_flow_x_integral; /**< accumulated optical flow in radians around x axis */
+ float pixel_flow_y_integral; /**< accumulated optical flow in radians around y axis */
+ float gyro_x_rate_integral; /**< accumulated gyro value in radians around x axis */
+ float gyro_y_rate_integral; /**< accumulated gyro value in radians around y axis */
+ float gyro_z_rate_integral; /**< accumulated gyro value in radians around z axis */
+ float ground_distance_m; /**< Altitude / distance to ground in meters */
+ uint32_t integration_timespan; /**