diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart.cpp b/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart.cpp
new file mode 100644
index 0000000000..9cee004a59
--- /dev/null
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart.cpp
@@ -0,0 +1,276 @@
+/*
+   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/>.
+ */
+/*
+  driver for Pixart PMW3900DH optical flow sensor
+
+
+  NOTE: This sensor does not use traditional SPI register access. The
+  timing for register reads and writes is critical
+ */
+
+#include <AP_HAL/AP_HAL.h>
+#include <AP_Math/edc.h>
+#include <utility>
+#include "OpticalFlow.h"
+#include "AP_OpticalFlow_Pixart_SROM.h"
+#include <stdio.h>
+
+extern const AP_HAL::HAL& hal;
+
+#define PIXART_REG_PRODUCT_ID  0x00
+#define PIXART_REG_REVISION_ID 0x01
+#define PIXART_REG_MOTION      0x02
+#define PIXART_REG_DELTA_X_L   0x03
+#define PIXART_REG_DELTA_X_H   0x04
+#define PIXART_REG_DELTA_Y_L   0x05
+#define PIXART_REG_DELTA_Y_H   0x06
+#define PIXART_REG_SQUAL       0x07
+#define PIXART_REG_RAWDATA_SUM 0x08
+#define PIXART_REG_RAWDATA_MAX 0x09
+#define PIXART_REG_RAWDATA_MIN 0x0A
+#define PIXART_REG_SHUTTER_LOW 0x0B
+#define PIXART_REG_SHUTTER_HI  0x0C
+#define PIXART_REG_CONFIG1     0x0F
+#define PIXART_REG_CONFIG2     0x10
+#define PIXART_REG_FRAME_CAP   0x12
+#define PIXART_REG_SROM_EN     0x13
+#define PIXART_REG_RUN_DS      0x14
+#define PIXART_REG_REST1_RATE  0x15
+#define PIXART_REG_REST1_DS    0x16
+#define PIXART_REG_REST2_RATE  0x17
+#define PIXART_REG_REST2_DS    0x18
+#define PIXART_REG_REST3_RATE  0x19
+#define PIXART_REG_OBS         0x24
+#define PIXART_REG_DOUT_L      0x25
+#define PIXART_REG_DOUT_H      0x26
+#define PIXART_REG_RAW_GRAB    0x29
+#define PIXART_REG_SROM_ID     0x2A
+#define PIXART_REG_POWER_RST   0x3A
+#define PIXART_REG_SHUTDOWN    0x3B
+#define PIXART_REG_INV_PROD_ID 0x3F
+#define PIXART_REG_MOT_BURST   0x50
+#define PIXART_REG_SROM_BURST  0x62
+#define PIXART_REG_RAW_BURST   0x64
+
+// writing to registers needs this flag
+#define PIXART_WRITE_FLAG      0x80
+
+// timings in microseconds
+#define PIXART_Tsrad           150
+
+// correct result for SROM CRC
+#define PIXART_SROM_CRC_RESULT 0xBEEF
+
+// constructor
+AP_OpticalFlow_Pixart::AP_OpticalFlow_Pixart(OpticalFlow &_frontend) :
+OpticalFlow_backend(_frontend)
+{
+    _dev = std::move(hal.spi->get_device("external0m3"));
+}
+
+
+// detect the device
+AP_OpticalFlow_Pixart *AP_OpticalFlow_Pixart::detect(OpticalFlow &_frontend)
+{
+    AP_OpticalFlow_Pixart *sensor = new AP_OpticalFlow_Pixart(_frontend);
+    if (!sensor) {
+        return nullptr;
+    }
+    if (!sensor->setup_sensor()) {
+        delete sensor;
+        return nullptr;
+    }
+    return sensor;
+}
+
+// setup the device
+bool AP_OpticalFlow_Pixart::setup_sensor(void)
+{
+    if (!_dev->get_semaphore()->take(0)) {
+        AP_HAL::panic("Unable to get bus semaphore");
+    }
+
+    uint8_t id;
+    uint16_t crc;
+
+    // power-up sequence
+    reg_write(PIXART_REG_POWER_RST, 0x5A);
+    hal.scheduler->delay(50);
+
+    // check product ID
+    if (reg_read(PIXART_REG_PRODUCT_ID) != 0x3F ||
+        reg_read(PIXART_REG_INV_PROD_ID) != 0xC0) {
+        goto failed;
+    }
+    
+    srom_download();
+
+    id = reg_read(PIXART_REG_SROM_ID);
+    if (id != srom_id) {
+        printf("Pixart: bad SROM ID: 0x%02x\n", id);
+        goto failed;
+    }
+
+    reg_write(PIXART_REG_SROM_EN, 0x15);
+    hal.scheduler->delay(10);
+    
+    crc = reg_read16u(PIXART_REG_DOUT_L);
+    if (crc != 0xBEEF) {
+        printf("Pixart: bad SROM CRC: 0x%04x\n", crc);
+        goto failed;
+    }
+    
+    load_configuration();
+
+    hal.scheduler->delay(50);
+
+    printf("Pixart ready: prod:0x%02x rev:0x%02x iprod:0x%02x shi:0x%02x cfg1:0x%02x cfg2:0x%02x\n",
+           (unsigned)reg_read(PIXART_REG_PRODUCT_ID),
+           (unsigned)reg_read(PIXART_REG_REVISION_ID),
+           (unsigned)reg_read(PIXART_REG_INV_PROD_ID),
+           (unsigned)reg_read(PIXART_REG_SHUTTER_HI),
+           (unsigned)reg_read(PIXART_REG_CONFIG1),
+           (unsigned)reg_read(PIXART_REG_CONFIG2));
+
+    _dev->get_semaphore()->give();
+
+    _dev->register_periodic_callback(2000, FUNCTOR_BIND_MEMBER(&AP_OpticalFlow_Pixart::timer, bool));
+    return true;
+
+failed:
+    _dev->get_semaphore()->give();
+    return false;
+}
+
+// update - read latest values from sensor and fill in x,y and totals.
+void AP_OpticalFlow_Pixart::update(void)
+{
+}
+
+// write an 8 bit register
+void AP_OpticalFlow_Pixart::reg_write(uint8_t reg, uint8_t value)
+{
+    _dev->write_register(reg | PIXART_WRITE_FLAG, value);
+    hal.scheduler->delay_microseconds(120);
+}
+
+// read from an 8 bit register
+uint8_t AP_OpticalFlow_Pixart::reg_read(uint8_t reg)
+{
+    uint8_t v = 0;
+    _dev->set_chip_select(true);
+    _dev->transfer(&reg, 1, nullptr, 0);
+    hal.scheduler->delay_microseconds(PIXART_Tsrad);
+    _dev->transfer(nullptr, 0, &v, 1);
+    _dev->set_chip_select(false);
+    hal.scheduler->delay_microseconds(120);
+    return v;
+}
+
+// read from a 16 bit unsigned register
+uint16_t AP_OpticalFlow_Pixart::reg_read16u(uint8_t reg)
+{
+    uint16_t low = reg_read(reg);
+    uint16_t high = reg_read(reg+1);
+    return low | (high<<8);
+}
+
+// read from a 16 bit signed register
+int16_t AP_OpticalFlow_Pixart::reg_read16s(uint8_t reg)
+{
+    return (int16_t)reg_read16u(reg);
+}
+
+
+void AP_OpticalFlow_Pixart::srom_download(void)
+{
+    reg_write(0x39, 0x02);
+    hal.scheduler->delay(1);
+    reg_write(PIXART_REG_SROM_EN, 0x1D);
+    hal.scheduler->delay(10);
+    reg_write(PIXART_REG_SROM_EN, 0x18);
+
+    if (!_dev->set_chip_select(true)) {
+        printf("Failed to force CS\n");
+    }
+    hal.scheduler->delay_microseconds(1);
+    uint8_t reg = PIXART_REG_SROM_BURST | PIXART_WRITE_FLAG;
+    _dev->transfer(&reg, 1, nullptr, 0);
+
+    for (uint16_t i = 0; i < ARRAY_SIZE(srom_data); i++) {
+        hal.scheduler->delay_microseconds(15);
+        _dev->transfer(&srom_data[i], 1, nullptr, 0);
+    }
+
+    hal.scheduler->delay_microseconds(125);
+    if (!_dev->set_chip_select(false)) {
+        printf("Failed to force CS off\n");
+    }
+    hal.scheduler->delay_microseconds(160);
+}
+
+void AP_OpticalFlow_Pixart::load_configuration(void)
+{
+    for (uint16_t i = 0; i < ARRAY_SIZE(init_data); i++) {
+        reg_write(init_data[i].reg, init_data[i].value);
+    }
+}
+
+
+void AP_OpticalFlow_Pixart::motion_burst(void)
+{
+    uint8_t *b = (uint8_t *)&burst;
+
+    burst.delta_x = 0;
+    burst.delta_y = 0;
+    
+    _dev->set_chip_select(true);
+    uint8_t reg = PIXART_REG_MOT_BURST;
+
+    _dev->transfer(&reg, 1, nullptr, 0);
+    hal.scheduler->delay_microseconds(150);
+
+    for (uint8_t i=0; i<sizeof(burst); i++) {
+        _dev->transfer(nullptr, 0, &b[i], 1);
+        if (i == 0 && (burst.motion & 0x80) == 0) {
+            // no motion, save some bus bandwidth
+            _dev->set_chip_select(false);
+            return;
+        }
+    }
+    _dev->set_chip_select(false);
+}
+
+bool AP_OpticalFlow_Pixart::timer(void)
+{
+    if (AP_HAL::micros() - last_burst_us < 500) {
+        return true;
+    }
+    motion_burst();
+    last_burst_us = AP_HAL::micros();
+    
+    sum_x += burst.delta_x;
+    sum_y += burst.delta_y;
+
+    uint32_t now = AP_HAL::millis();
+    if (now - last_print_ms >= 100 && (sum_x != 0 || sum_y != 0)) {
+        last_print_ms = now;
+        printf("Motion: %d %d obs:0x%02x squal:%u rds:%u maxr:%u minr:%u sup:%u slow:%u\n",
+               (int)sum_x, (int)sum_y, (unsigned)burst.squal, (unsigned)burst.rawdata_sum, (unsigned)burst.max_raw,
+               (unsigned)burst.max_raw, (unsigned)burst.min_raw, (unsigned)burst.shutter_upper, (unsigned)burst.shutter_lower);
+        sum_x = sum_y = 0;
+    }
+    return true;
+}
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart.h b/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart.h
new file mode 100644
index 0000000000..c443137088
--- /dev/null
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart.h
@@ -0,0 +1,64 @@
+#pragma once
+
+#include "OpticalFlow.h"
+#include <AP_HAL/utility/OwnPtr.h>
+
+class AP_OpticalFlow_Pixart : public OpticalFlow_backend
+{
+public:
+    /// constructor
+    AP_OpticalFlow_Pixart(OpticalFlow &_frontend);
+
+    // init - initialise the sensor
+    void init() override {}
+
+    // update - read latest values from sensor and fill in x,y and totals.
+    void update(void) override;
+
+    // detect if the sensor is available
+    static AP_OpticalFlow_Pixart *detect(OpticalFlow &_frontend);
+
+private:
+    AP_HAL::OwnPtr<AP_HAL::SPIDevice> _dev;
+
+    struct RegData {
+        uint8_t reg;
+        uint8_t value;
+    };
+
+    struct PACKED MotionBurst {
+        uint8_t motion;
+        uint8_t observation;
+        int16_t delta_x;
+        int16_t delta_y;
+        uint8_t squal;
+        uint8_t rawdata_sum;
+        uint8_t max_raw;
+        uint8_t min_raw;
+        uint8_t shutter_upper;
+        uint8_t shutter_lower;
+    } burst;
+    
+    static const uint8_t srom_data[];
+    static const uint8_t srom_id;
+    static const RegData init_data[];
+
+    // setup sensor
+    bool setup_sensor(void);
+    
+    void reg_write(uint8_t reg, uint8_t value);
+    uint8_t reg_read(uint8_t reg);
+    int16_t reg_read16s(uint8_t reg);
+    uint16_t reg_read16u(uint8_t reg);
+
+    void srom_download(void);
+    void load_configuration(void);
+
+    bool timer(void);
+    void motion_burst(void);
+
+    int32_t sum_x;
+    int32_t sum_y;
+    uint32_t last_print_ms;
+    uint32_t last_burst_us;
+};
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart_SROM.h b/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart_SROM.h
new file mode 100644
index 0000000000..335b6dfb66
--- /dev/null
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_Pixart_SROM.h
@@ -0,0 +1,280 @@
+/*
+  SROM for Pixart flow, converted from data supplied by Pixart (thanks to Fish for conversion)
+ */
+
+const uint8_t AP_OpticalFlow_Pixart::srom_id = 0xED;
+
+const uint8_t AP_OpticalFlow_Pixart::srom_data[] =
+{
+    0x03, 0xed, 0xb5, 0x32, 0x26, 0xfc, 0x1e, 0xbe, 0xd8, 0x1d, 0xb8, 0xd3, 0x05, 0x88, 0x73, 0x45,
+    0x08, 0x92, 0xa6, 0xce, 0x1e, 0xba, 0xfe, 0x71, 0x5f, 0x1d, 0xb8, 0xf2, 0x66, 0x2f, 0xdc, 0x1b,
+    0x95, 0xa8, 0xb3, 0xe4, 0x2b, 0xb5, 0xe8, 0x52, 0x26, 0xce, 0xff, 0x5d, 0x38, 0xf2, 0x66, 0x4e,
+    0xff, 0x5d, 0x38, 0xd3, 0x05, 0x6f, 0x31, 0xe0, 0x42, 0x06, 0x8e, 0x7f, 0x7c, 0x5b, 0x34, 0xcb,
+    0xf5, 0x68, 0x52, 0x26, 0xce, 0xff, 0x7c, 0x7a, 0x76, 0x6e, 0x3f, 0xdd, 0x19, 0xb3, 0xc3, 0x06,
+    0x8a, 0x96, 0x8f, 0x9c, 0x9b, 0x95, 0x81, 0x90, 0x83, 0x84, 0x6a, 0x54, 0x0b, 0x75, 0x49, 0x10,
+    0x83, 0x60, 0x41, 0x18, 0x8c, 0x61, 0x34, 0xfe, 0x68, 0xe6, 0xa1, 0x61, 0x44, 0x81, 0x7d, 0xc3,
+    0xc7, 0xcf, 0x96, 0x11, 0x65, 0x14, 0x2d, 0xa7, 0xe1, 0x91, 0xe6, 0xfa, 0x99, 0x04, 0x65, 0x1d,
+    0x57, 0x98, 0x7c, 0xce, 0x9a, 0xe2, 0x41, 0xd5, 0x0e, 0x3b, 0x51, 0xed, 0x0f, 0x55, 0x45, 0xc0,
+    0xbc, 0x32, 0x00, 0xcb, 0x3e, 0x84, 0xba, 0x7a, 0x59, 0x84, 0x04, 0x5f, 0xf2, 0xf3, 0x8b, 0x20,
+    0x2d, 0x6c, 0xb5, 0x88, 0x9c, 0x4c, 0x4c, 0x70, 0x45, 0x13, 0x8a, 0x9a, 0x93, 0x64, 0x2b, 0xf5,
+    0xa8, 0x7d, 0x63, 0x78, 0xcc, 0xd0, 0xa6, 0x6e, 0x54, 0xff, 0xc9, 0x67, 0x40, 0xe0, 0x4c, 0xdd,
+    0x48, 0x58, 0xff, 0xb6, 0x80, 0x95, 0xb5, 0xc3, 0x2b, 0x19, 0x2b, 0x8c, 0x19, 0x66, 0x1a, 0xc6,
+    0xac, 0x2e, 0x4a, 0x9f, 0xcc, 0x1e, 0xe6, 0xed, 0x36, 0x2d, 0x63, 0xb4, 0x9b, 0xb9, 0xbf, 0xd9,
+    0x22, 0xde, 0xaf, 0xcc, 0xde, 0x02, 0xa3, 0xf7, 0x9a, 0xa5, 0x27, 0x64, 0x19, 0x82, 0x16, 0xdc,
+    0xf5, 0x21, 0x93, 0x54, 0xdf, 0x4e, 0x4d, 0x99, 0xac, 0x89, 0x55, 0x3b, 0xb1, 0x73, 0x56, 0x7e,
+    0xed, 0x28, 0x46, 0x5d, 0xc6, 0xe7, 0x1f, 0x7f, 0x4c, 0x68, 0x4d, 0x71, 0xf3, 0xa4, 0x5f, 0x41,
+    0x9b, 0xe9, 0x23, 0xed, 0x1b, 0xa5, 0xc4, 0x6c, 0x35, 0xb2, 0xfa, 0x82, 0x1e, 0x28, 0xab, 0xf1,
+    0x53, 0xb7, 0x4f, 0xf1, 0x00, 0x77, 0xe4, 0x3a, 0x34, 0xe7, 0x4f, 0xfe, 0xbb, 0x84, 0x08, 0x79,
+    0x3d, 0x39, 0x90, 0xd2, 0x85, 0x83, 0x0b, 0x76, 0x8a, 0xc7, 0x8e, 0x96, 0xc6, 0x88, 0xbe, 0xfa,
+    0x2e, 0x5c, 0x28, 0x2b, 0xa4, 0x69, 0x59, 0xff, 0x07, 0x5f, 0x68, 0x85, 0xd0, 0xe6, 0x1c, 0x88,
+    0x2f, 0xe5, 0x10, 0xe0, 0x55, 0x1b, 0xc4, 0xaa, 0x91, 0x2d, 0x69, 0xd2, 0x13, 0x91, 0xb1, 0x40,
+    0x25, 0x87, 0xbd, 0x5b, 0x00, 0x75, 0x6c, 0x86, 0x09, 0xb8, 0x78, 0x70, 0xc1, 0x13, 0x1b, 0x5d,
+    0xca, 0x47, 0x8e, 0x6f, 0x25, 0x25, 0x53, 0x54, 0x8a, 0x5f, 0x8c, 0x6f, 0x0a, 0xd8, 0xa7, 0xad,
+    0xac, 0xc8, 0x73, 0x59, 0xc0, 0x5a, 0x75, 0x95, 0xe8, 0xe6, 0x9b, 0xa8, 0xc0, 0x7a, 0x68, 0x15,
+    0xf6, 0x2e, 0x1e, 0xff, 0x57, 0xf9, 0xe4, 0xfc, 0xf4, 0xff, 0x8f, 0xb1, 0xc5, 0xf6, 0x22, 0xf6,
+    0xba, 0xb2, 0xd5, 0x88, 0x7e, 0x8f, 0x93, 0x56, 0x32, 0x7c, 0x2d, 0xa0, 0xc1, 0x3f, 0x96, 0x24,
+    0xf0, 0x75, 0xe7, 0x17, 0x8d, 0x98, 0x19, 0x8c, 0x0b, 0xfa, 0xd4, 0x98, 0x3e, 0x2f, 0x59, 0xf5,
+    0x03, 0x23, 0x4b, 0xa0, 0xbe, 0xca, 0x3b, 0xcd, 0x39, 0xf1, 0x75, 0x4d, 0x2b, 0x17, 0x58, 0x2b,
+    0x55, 0x15, 0x53, 0x1b, 0x1e, 0xed, 0xce, 0xb2, 0x32, 0x5d, 0x30, 0x12, 0x37, 0xe7, 0xad, 0x59,
+    0x2c, 0x61, 0x35, 0x3f, 0x13, 0xd4, 0x8a, 0x4a, 0x8c, 0x0e, 0xec, 0xfd, 0xbf, 0xc1, 0xa0, 0x87,
+    0x24, 0x2a, 0x95, 0xf2, 0x5b, 0x14, 0xa6, 0xca, 0x96, 0x36, 0x07, 0x5e, 0x49, 0x3a, 0x54, 0x0f,
+    0x4e, 0xcd, 0xb8, 0xf8, 0xa7, 0xb9, 0xf9, 0xd4, 0x83, 0x64, 0x7e, 0x70, 0xea, 0xa6, 0x1b, 0x3a,
+    0xcb, 0xb1, 0xee, 0xdf, 0x53, 0x69, 0x13, 0x33, 0x94, 0xeb, 0x08, 0x39, 0x61, 0xe0, 0x68, 0x17,
+    0x58, 0xe9, 0x91, 0xb0, 0x40, 0x3b, 0x38, 0x08, 0x46, 0x0a, 0xaf, 0x7e, 0xb4, 0xc4, 0x7a, 0xb4,
+    0xcc, 0x09, 0xe0, 0xe1, 0x46, 0x7a, 0x8c, 0x4e, 0xaf, 0x1b, 0x04, 0x7b, 0x64, 0x10, 0x83, 0xa1,
+    0xf3, 0xf5, 0x49, 0x9b, 0x77, 0xcd, 0xff, 0xb0, 0x4b, 0x86, 0x0c, 0x89, 0x4a, 0x13, 0x22, 0x0a,
+    0x1e, 0x2c, 0x78, 0xa7, 0x9e, 0x0f, 0x7a, 0x2c, 0x78, 0x85, 0xcc, 0xcb, 0xf7, 0x78, 0x41, 0x26,
+    0x5f, 0x9d, 0x22, 0x19, 0x71, 0xcf, 0x9a, 0x59, 0x4b, 0xe4, 0x7a, 0x5f, 0x61, 0xc2, 0xf7, 0xc1,
+    0xd4, 0x62, 0x91, 0x7b, 0x5d, 0xc5, 0x05, 0xe1, 0x40, 0x35, 0xa0, 0x24, 0x73, 0x4d, 0xf3, 0x37,
+    0xa1, 0xba, 0xd8, 0xa9, 0x0c, 0x21, 0xb6, 0xb7, 0xa9, 0xfe, 0x57, 0xf6, 0xbd, 0xcc, 0xa2, 0x42,
+    0x65, 0x0f, 0xc4, 0xb1, 0x03, 0xd0, 0xfb, 0xd3, 0xa2, 0xd8, 0x7b, 0x2e, 0x4c, 0x0f, 0x05, 0x2b,
+    0x5a, 0x01, 0xf8, 0x28, 0x30, 0x17, 0x75, 0xc3, 0x9a, 0xb8, 0xba, 0x4d, 0xea, 0x83, 0x3c, 0x20,
+    0x7c, 0x5d, 0x60, 0xf9, 0xd3, 0x91, 0x79, 0x8a, 0x78, 0xd1, 0x24, 0x4a, 0xec, 0x29, 0x64, 0xe5,
+    0xb3, 0xb9, 0xd9, 0x6b, 0xc1, 0x5c, 0x77, 0x03, 0x27, 0xac, 0x50, 0xff, 0xa2, 0x97, 0xee, 0x3a,
+    0x14, 0xb3, 0x46, 0xad, 0xeb, 0xb5, 0x6c, 0x01, 0x15, 0x34, 0xc6, 0x40, 0x80, 0x6d, 0xcc, 0xa6,
+    0x31, 0x71, 0xa2, 0xc5, 0xe6, 0x97, 0x8e, 0x3d, 0x0b, 0x54, 0x89, 0x50, 0xdf, 0xa5, 0x10, 0xe7,
+    0xf1, 0xa6, 0x44, 0xd6, 0x1e, 0x34, 0x1c, 0x8d, 0xcf, 0xfb, 0xc5, 0xeb, 0x93, 0x11, 0x7f, 0x51,
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+    0x64, 0x01, 0x07, 0x0e, 0x28, 0x7c, 0x1f, 0x01, 0x37, 0x40, 0x0a, 0xc4, 0x88, 0x26, 0xdc, 0xeb,
+    0x80, 0x23, 0x99, 0xca, 0x3e, 0x0b, 0x68, 0xbb, 0xe8, 0x0b, 0x77, 0xf3, 0x11, 0x1f, 0x23, 0x91,
+    0x7d, 0x85, 0xc0, 0x2b, 0xc5, 0x9c, 0x14, 0x5c, 0x25, 0x83, 0xbb, 0x0e, 0x29, 0xfa, 0x0f, 0x85,
+    0x5f, 0xc8, 0xb9, 0x07, 0x53, 0xf2, 0x60, 0xcb, 0xc3, 0xb2, 0x25, 0xa6, 0x35, 0x88, 0xfc, 0x55,
+    0xaf, 0xc6, 0x68, 0x19, 0xa4, 0x30, 0x65, 0xb2, 0xb5, 0x7b, 0xae, 0x7d, 0x1b, 0x4f, 0xca, 0x21,
+    0x1f, 0x46, 0xfb, 0x42, 0x6e, 0xfd, 0xd9, 0xc6, 0x81, 0x61, 0x75, 0xbe, 0x52, 0x0d, 0x3f, 0x58,
+    0xa8, 0x71, 0x6c, 0xce, 0x1d, 0x0f, 0x1e, 0xb3, 0x33, 0xf0, 0x7e, 0xb5, 0xbe, 0x05, 0x7a, 0x2a,
+    0xa8, 0x71, 0xb4, 0x2f, 0x9f, 0x1b, 0x30, 0xe1, 0x27, 0x29, 0xf2, 0xac, 0x19, 0x1e, 0x05, 0xe8,
+    0xbc, 0xd5, 0x89, 0xf3, 0x9f, 0x4b, 0x23, 0x3a, 0x2d, 0x0c, 0xac, 0x93, 0xc7, 0xad, 0xee, 0xd1,
+    0x44, 0x77, 0xba, 0x3b, 0xd8, 0x7a, 0xd2, 0x9d, 0xfa, 0x5d, 0xa0, 0xa0, 0x54, 0x68, 0x38, 0x08,
+    0xc6, 0xd2, 0xed, 0x0e, 0x65, 0x3a, 0xcb, 0x6a, 0xf5, 0xbc, 0x5e, 0x3d, 0x7e, 0xdb, 0x16, 0x28,
+    0x37, 0xef, 0x88, 0x31, 0xd3, 0x0d, 0xcc, 0x03, 0x40, 0xa3, 0x42, 0x2b, 0x5c, 0xa8, 0x50, 0x11,
+    0x99, 0xc0, 0xa1, 0xa8, 0x9d, 0x38, 0x07, 0x44, 0xef, 0xd7, 0xda, 0x14, 0x0f, 0xcf, 0x0e, 0x6e,
+    0xfc, 0x0a, 0xa6, 0xd2, 0x34, 0xa9, 0x82, 0x96, 0x1e, 0xc0, 0xe6, 0xa4, 0x5e, 0x6a, 0x5e, 0xfc,
+    0xae, 0x5f, 0x03, 0xcc, 0xd1, 0xf5, 0xcb, 0xae, 0x85, 0xcf, 0x47, 0x5d, 0x4a, 0x4f, 0x40, 0x22,
+    0xf3, 0xa6, 0xd8, 0x16, 0x09, 0x19, 0xe2, 0x84, 0xa3, 0x50, 0x75, 0x14, 0x0e, 0x01, 0x57, 0x01,
+    0xc1, 0xef, 0xd0, 0x60, 0x35, 0x49, 0x13, 0x67, 0xe5, 0xbd, 0xd3, 0xb0, 0x41, 0x72, 0x8d, 0xac,
+    0x8b, 0x16, 0xb8, 0x32, 0xf2, 0xc0, 0x79, 0x52, 0x4c, 0x84, 0x29, 0xa2, 0x0c, 0x0e, 0x37, 0x1b,
+    0xad, 0x3d, 0x0d, 0x1a, 0xa6, 0x02, 0xd2, 0x5e, 0x9b, 0xd1, 0x20, 0xa3, 0xc4, 0xeb, 0x54, 0x2a,
+    0xb7, 0xcd, 0xf9, 0x70, 0x62, 0x46, 0xef, 0x5c, 0x3a, 0xd7, 0x2c, 0xda, 0x17, 0x8d, 0x79, 0x51,
+    0x20, 0xc2, 0xe7, 0x4c, 0x1a, 0x97, 0xac, 0xda, 0x17, 0x8d, 0x98, 0x93, 0xa4, 0xca, 0x16, 0x8f,
+    0x9c, 0xba, 0xf6, 0x4f, 0x1c, 0xba, 0xd7, 0x2c, 0xda, 0x36, 0xee, 0x3f, 0xdd, 0x19, 0x91, 0xa0,
+    0xa3, 0xa5, 0xc8, 0x12, 0x87, 0x8c, 0x9a, 0xb6, 0xcf, 0xfd, 0x78, 0x53, 0x24, 0xca, 0x16, 0xae,
+    0xbf, 0xfc, 0x5b, 0x34, 0xcb, 0xf5, 0x68, 0x33, 0xc5, 0xe9, 0x50, 0x22, 0xc6, 0x0e, 0x7f, 0x5d,
+    0x38, 0xf2, 0x66, 0x2f, 0xbd, 0xd9, 0x11, 0xa0, 0xa3, 0xa5, 0xa9, 0xb1, 0xe0, 0x23, 0xa5, 0xa9,
+    0xb1, 0xc1, 0xe1, 0x21, 0xa1, 0xc0, 0x02, 0x67, 0x2d, 0xb9, 0xd1, 0x20, 0xc2, 0x06, 0x6f, 0x3d,
+    0xd9, 0x30, 0xc3, 0x04, 0x6b, 0x35, 0xc9, 0xf1, 0x60, 0x23, 0xc4, 0xeb, 0x35, 0xc9, 0x10, 0xa2,
+    0xa7, 0xcc, 0xfb, 0x55, 0x28, 0xd2, 0x26, 0xaf, 0xbd, 0xf8, 0x72, 0x47, 0xed, 0x39, 0xd1, 0x20,
+    0xa3, 0xc4, 0xeb, 0x35, 0xe8, 0x52, 0x26, 0xaf, 0xdc, 0x3a, 0xf6, 0x4f, 0xfd, 0x59, 0x30, 0xe2,
+    0x46, 0x0e, 0x7f, 0x5d, 0x19, 0x91, 0x81, 0x61, 0x21, 0xc0, 0xe3, 0x25, 0xa9, 0xb1, 0xe0, 0x42,
+    0x06, 0x6f, 0x3d, 0xf8, 0x72, 0x47, 0x0c, 0x7b, 0x74, 0x4b, 0x14, 0x8b, 0x75, 0x49, 0x10, 0x83,
+    0x84, 0x6b, 0x54, 0x0b, 0x94, 0x8b, 0x94, 0xaa, 0xb7, 0xec, 0xa2, 0xc7, 0x77, 0xd9,
+};
+
+
+/*
+  initialisation data (register config)
+ */
+const AP_OpticalFlow_Pixart::RegData AP_OpticalFlow_Pixart::init_data[] =
+{
+   { 0x30, 0x44 },
+
+   { 0x31, 0xe9 },
+   { 0x32, 0x82 },
+   { 0x33, 0xdf },
+
+   { 0x31, 0xea },
+   { 0x32, 0x82 },
+   { 0x33, 0xff },
+
+   { 0x31, 0xeb },
+   { 0x32, 0x82 },
+   { 0x33, 0xdf },
+
+   { 0x31, 0xec },
+   { 0x32, 0x82 },
+   { 0x33, 0xff },
+
+   { 0x31, 0xed },
+   { 0x32, 0x82 },
+   { 0x33, 0xdf },
+
+   { 0x31, 0xee },
+   { 0x32, 0x82 },
+   { 0x33, 0xff },
+
+
+   { 0x31, 0xdd },
+   { 0x32, 0x82 },
+   { 0x33, 0xfe },
+
+   { 0x31, 0xde },
+   { 0x32, 0x82 },
+   { 0x33, 0x0b },
+
+   { 0x31, 0xdf },
+   { 0x32, 0x82 },
+   { 0x33, 0xfe },
+
+   { 0x31, 0xe0 },
+   { 0x32, 0x82 },
+   { 0x33, 0x0b },
+
+   { 0x31, 0xe1 },
+   { 0x32, 0x82 },
+   { 0x33, 0xfe },
+
+   { 0x31, 0xe2 },
+   { 0x32, 0x82 },
+   { 0x33, 0x0b },
+
+   { 0x47, 0x00 },
+   { 0x10, 0x08 },
+
+   { 0x0f, 0x28 },
+   { 0x2b, 0x08 },
+   { 0x2c, 0x10 },
+   { 0x2e, 0x1f },
+
+   { 0x49, 0x40 },
+   { 0x4a, 0x60 },
+   { 0x4b, 0x3F },
+
+   { 0x10, 0x08 },
+   { 0x30, 0x00 },
+
+   { 0x45, 0x8b },
+   { 0x46, 0x02 },
+   { 0x53, 0x07 },
+   { 0x52, 0x10 },
+};
+
diff --git a/libraries/AP_OpticalFlow/OpticalFlow.cpp b/libraries/AP_OpticalFlow/OpticalFlow.cpp
index 22d6f18e85..2e6a6969e7 100644
--- a/libraries/AP_OpticalFlow/OpticalFlow.cpp
+++ b/libraries/AP_OpticalFlow/OpticalFlow.cpp
@@ -1,3 +1,4 @@
+#include <AP_BoardConfig/AP_BoardConfig.h>
 #include "OpticalFlow.h"
 #include "AP_OpticalFlow_Onboard.h"
 
@@ -74,7 +75,13 @@ void OpticalFlow::init(void)
 {
     if (!backend) {
 #if CONFIG_HAL_BOARD == HAL_BOARD_PX4 || CONFIG_HAL_BOARD == HAL_BOARD_VRBRAIN
-        backend = new AP_OpticalFlow_PX4(*this);
+        if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_PIXHAWK) {
+            // possibly have pixhart on external SPI
+            backend = AP_OpticalFlow_Pixart::detect(*this);
+        }
+        if (backend == nullptr) {
+            backend = new AP_OpticalFlow_PX4(*this);
+        }
 #elif CONFIG_HAL_BOARD == HAL_BOARD_SITL
         backend = new AP_OpticalFlow_HIL(*this);
 #elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BEBOP ||\
diff --git a/libraries/AP_OpticalFlow/OpticalFlow.h b/libraries/AP_OpticalFlow/OpticalFlow.h
index 793c6c4505..7d7a8928a9 100644
--- a/libraries/AP_OpticalFlow/OpticalFlow.h
+++ b/libraries/AP_OpticalFlow/OpticalFlow.h
@@ -103,3 +103,4 @@ private:
 #include "AP_OpticalFlow_HIL.h"
 #include "AP_OpticalFlow_PX4.h"
 #include "AP_OpticalFlow_Linux.h"
+#include "AP_OpticalFlow_Pixart.h"
diff --git a/libraries/AP_OpticalFlow/OpticalFlow_backend.cpp b/libraries/AP_OpticalFlow/OpticalFlow_backend.cpp
index 2341cf7f4f..2c867d80f1 100644
--- a/libraries/AP_OpticalFlow/OpticalFlow_backend.cpp
+++ b/libraries/AP_OpticalFlow/OpticalFlow_backend.cpp
@@ -23,6 +23,13 @@ OpticalFlow_backend::OpticalFlow_backend(OpticalFlow &_frontend) :
     _sem = hal.util->new_semaphore();    
 }
 
+OpticalFlow_backend::~OpticalFlow_backend(void)
+{
+    if (_sem) {
+        delete _sem;
+    }
+}
+
 // update the frontend
 void OpticalFlow_backend::_update_frontend(const struct OpticalFlow::OpticalFlow_state &state)
 {
diff --git a/libraries/AP_OpticalFlow/OpticalFlow_backend.h b/libraries/AP_OpticalFlow/OpticalFlow_backend.h
index e0e4226f11..a562af97da 100644
--- a/libraries/AP_OpticalFlow/OpticalFlow_backend.h
+++ b/libraries/AP_OpticalFlow/OpticalFlow_backend.h
@@ -27,7 +27,8 @@ class OpticalFlow_backend
 public:
     // constructor
     OpticalFlow_backend(OpticalFlow &_frontend);
-
+    virtual ~OpticalFlow_backend(void);
+    
     // init - initialise sensor
     virtual void init() = 0;