From 9aad996b04c0c476a61258ff53498ea1184827a2 Mon Sep 17 00:00:00 2001
From: Daniel Agar <daniel@agar.ca>
Date: Sat, 17 Aug 2019 10:57:59 -0400
Subject: [PATCH] PMW3901 add register write delay (TIME_us_TSWW)

---
 src/drivers/optical_flow/pmw3901/PMW3901.cpp | 5 +++++
 src/drivers/optical_flow/pmw3901/PMW3901.hpp | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/drivers/optical_flow/pmw3901/PMW3901.cpp b/src/drivers/optical_flow/pmw3901/PMW3901.cpp
index 5c91a4f175..eca9a6d16e 100644
--- a/src/drivers/optical_flow/pmw3901/PMW3901.cpp
+++ b/src/drivers/optical_flow/pmw3901/PMW3901.cpp
@@ -33,6 +33,8 @@
 
 #include "PMW3901.hpp"
 
+static constexpr uint32_t TIME_us_TSWW = 11; //  - actually 10.5us
+
 PMW3901::PMW3901(int bus, enum Rotation yaw_rotation) :
 	SPI("PMW3901", PMW3901_DEVICE_PATH, bus, PMW3901_SPIDEV, SPIDEV_MODE0, PMW3901_SPI_BUS_SPEED),
 	ScheduledWorkItem(px4::device_bus_to_wq(get_device_id())),
@@ -71,6 +73,7 @@ PMW3901::sensorInit()
 	usleep(1000);
 
 	// set performance optimization registers
+	// from PixArt PMW3901MB Optical Motion Tracking chip demo kit V3.20 (21 Aug 2018)
 	unsigned char v = 0;
 	unsigned char c1 = 0;
 	unsigned char c2 = 0;
@@ -287,6 +290,8 @@ PMW3901::writeRegister(unsigned reg, uint8_t data)
 		return ret;
 	}
 
+	px4_usleep(TIME_us_TSWW);
+
 	return ret;
 }
 
diff --git a/src/drivers/optical_flow/pmw3901/PMW3901.hpp b/src/drivers/optical_flow/pmw3901/PMW3901.hpp
index fea69cf9bf..b55dddf437 100644
--- a/src/drivers/optical_flow/pmw3901/PMW3901.hpp
+++ b/src/drivers/optical_flow/pmw3901/PMW3901.hpp
@@ -41,7 +41,7 @@
 #include <px4_config.h>
 #include <px4_defines.h>
 #include <px4_getopt.h>
-#include <px4_work_queue/ScheduledWorkItem.hpp>
+#include <px4_platform_common/px4_work_queue/ScheduledWorkItem.hpp>
 #include <drivers/device/spi.h>
 #include <conversion/rotation.h>
 #include <lib/perf/perf_counter.h>