Cheerson CX-OF low cost optical flow sensor testing

Tim_D · May 3, 2019, 4:49pm

That would be very cool!!

Once I get my head around this module I might try to write a driver so that I can use it.

bys_1123 · May 3, 2019, 4:51pm

bys_1123 · May 3, 2019, 5:06pm

DimianZhan/UP-FLOW-Driver/blob/master/upflow.c

#include <stdio.h>
#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <errno.h>
#include <math.h>
#include <drivers/drv_hrt.h>
#include <systemlib/err.h>
#include <fcntl.h>
#include <systemlib/mavlink_log.h>
#include <uORB/uORB.h>
#include <uORB/topics/optical_flow.h>
//#include <uORB/topics/vehicle_attitude.h>
#include <px4_defines.h>
#include <px4_config.h>
#include <px4_posix.h>
#include <px4_shutdown.h>
#include <px4_tasks.h>

This file has been truncated. show original

FYI, Here is a draft C version driver for PX4 by Tonser from SJTU.

Official decode demo.

Fusion demo

Tim_D · May 3, 2019, 5:19pm

Thank you this was very kind of you!

bys_1123 · May 3, 2019, 5:31pm

Tim_D · May 3, 2019, 5:34pm

Not sure what the green box on the right it for.

I should be able to copy the AP_OpticalFlow_CXOF class and but change the point in the buffer where the correct data is?

Im not sure where “CXOF_PIXEL_SCALING” is coming from?

bys_1123 · May 3, 2019, 5:39pm

Congratulations, you made the GUI tool work.
BTW, you can use ‘i’ key to init the device, ‘c’ key to reset SUM.

bys_1123 · May 3, 2019, 5:45pm

github.com

DimianZhan/UP-FLOW-Driver/blob/master/upflow.c#L207


 orb_advert_t flow_data_handle = orb_advertise(ORB_ID(optical_flow), &flow_data);//公告这个主题
 //  orb_advert_t flow_data_handle = orb_advertise(ORB_ID(upixels_flow), &flow_data);//公告这个主题


 // 测试订阅程序
 // int test_sub_handle = orb_subscribe(ORB_ID(upixels_flow));
 // struct upixels_flow_s test_sub;


 // int counter = 0;
 uint64_t _previous_collect_timestamp = hrt_absolute_time();
 uint64_t _flow_dt_sum_usec = 0;
 float scale = 1.3f;
//    int vehicle_attitude_sub = orb_subscribe(ORB_ID(vehicle_attitude));
 while(thread_running)
{
     // PX4_WARN("warnxxxxxxxxxxxx!!!!");
     //解码 串口信息
 	read(uart_read,&data,1);
     if((data == 0xFE))
     {
         data = '0';
         read(uart_read,&data,1);

Tonser told me this is an experience number, just like an OPTICAL_FLOW_P.
Maybe there is a way to calculate it. But also this won’t hold you back.

bys_1123 · May 4, 2019, 9:24am

I think the scale can also adjust like this.

bys_1123 · May 5, 2019, 9:35am

There is lots of Optical Flow Module in china, if has a driver can be configuration to support them all is best, since they are very similar.

Tim_D · May 6, 2019, 2:25pm

Well at this point my concern is we wont get the upflow driver let alone any other driver… Might want to remove it from the wiki if we are not going to get support for it.

bys_1123 · May 13, 2019, 2:44am

Wow! This one is compatible with CX-OF.

rmackay9 · May 13, 2019, 3:53am

@bys_1123, great news! Is there a link to a store where it can be purchased. I should update the wiki to tell users which will/won’t work.

bys_1123 · May 13, 2019, 4:05am

It’s only in Taobao china now, I keep follow this, if it show up on other online shop, I’ll share the link here.

bys_1123 · May 13, 2019, 4:10am

I tested it, works really well.

Thanks for your work, makes lots of fun.

anbello · May 13, 2019, 8:20pm

Should be the same

anbello · May 14, 2019, 12:17pm

Interesting, it seems they have applied a lens in front of the P3901 sensor.

bys_1123 · May 14, 2019, 1:27pm

Yes, This one avoid dust into the sensor.

ppoirier · May 16, 2019, 12:16am

Just received the JJRC H62 RC Quadcopter Spare Parts Optical Current Board H62-03

So it is using same Data Format as UPIXELS UP-Flow

01 0xFE
02 0x0A
03 flow_x_integral low byte
04 flow_x_integral high byte
05 flow_y_integral low byte
06 flow_y_integral high byte
07 integration_timespan low byte
08 integration_timespan high byte
09 ground_distance low byte current not work, 0x03E7 in default.
10 ground_distance high byte current not work, 0x03E7 in default.
11 valid 0x00 or 0xF5
12 version
13 Xor Byte3~Byte12
14 0x55

Here is the result

My first impression is not that great, as this sensor has no qual (surface quality), requires more light , it is noisier and there is a scaling issue between axes

bys_1123 · May 30, 2019, 5:07pm

This compatible module will available on Seeed Studio at June.

https://www.seeedstudio.com/ThoneFlow_3901U_UART_Serial_Version_PMW3901_Optical_Flow_Sensor-p-4040.html