QHY174GPS

QHY174GPS是全球领先的一款内置GPS高精度时间标记的高速CMOS相机。能够将CMOS的开始曝光时刻和结束曝光时刻以硬件时间戳的方式记录到相机的图像数据中，并且精度可以达到全球范围内，与GPS的原子钟的误差1微秒。这对高速时域应用而言非常重要，非常适合于掩星观测。2017年，美国宇航局（NASA）的新视野号团队，使用了20多台QHY174GPS相机，对柯伊伯带小天体2014MU69进行了掩星观测。在三次观测机会中，2017年7月17日在阿根廷的观测取得了成功，获得了距离地球60亿千米的2014MU69的掩星图像。被誉为“天文学历史上最具有挑战性的一次掩星观测”。观测获得了小行星的精确形貌，尺寸，轨道，以及周边情况等参数，用于指导2019年元旦新视野号近距离飞越2014MU69。2019年1月1日新视野号成功飞越2014MU69，并且发回了这颗遥远小行星的照片。其形状与使用QHY174GPS在地面进行的掩星观测所拍摄到的形状完全吻合。这也证明了QHY174GPS取得的科学数据是准确而成功的。

please download the software from this link:

注意：最后一个版本添加了连续帧保存功能。

5.运行EasyTimeStamp软件。 您将看到视频出现在easyTimeStamp软件上。 然后单击“OnAir”按钮。 视频流将发送到AMCAP。

请参阅QHYCCD API的帮助文档以执行基本图像操作。 以下是操作GPS部件的附加API。

请不要将频率调整到超过10,000,500的计数器。 因为FPGA会认为10,000,500是PPS信号丢失的条件。

set_GPS_VCOX_Freq(unsigned short i);  The input range of i is 0-4095

Set the Calibration LED Enable
set_GPS_LEDCAL_Mode(unsigned char i);
i=0:disable LED light    1:enable LED light

Set LED pulse position for shutter starting exposure
set_GPS_POSA(unsigned char is_slave,unsigned long pos,unsigned char width);

Set LED pulse position for shutter ending exposure
set_GPS_POSB(unsigned char is_slave,unsigned long pos,unsigned char width);

Set Master/Slave Mode
set_GPS_MasterSlave(unsigned char i);
i=0: Master mode   1:Slave mode

When in slave mode, set the parameter.
set_GPS_SlaveMode_Parameter(unsigned long target_sec,unsigned int target_us,unsigned int deltaT_sec,unsigned int deltaT_us,unsigned int expTime)

The target_sec is the “JS” that QHYCCD defined. It is reference to a time.

Image Heady的数据结构调用API：

相机记录GPS信息并插入每个帧的头部。 该功能可以通过API启用
ret=SetQHYCCDParam(g_hCam,CAM_GPS,1);

并可以通过调用API禁用：
ret=SetQHYCCDParam(g_hCam,CAM_GPS,0);

ImageHead Shift

序列号是帧的硬件计数器。 它将从零开始，每帧将添加一个。 它将从cmos相机开始工作开始
0  Sequence Number MSB
1  Sequence Number
2  Sequence Number
3  Sequence Number LSB

4 temporary Sequence Number   (Normally no use)

5 Image Width  MSB
6 Image Width LSB

7 Image Height MSB
8 Image Height LSB

Latitude is the current latitude report by GPS.
9    latitude MSB
10  latitude
11  latitude
12  latitude LSB

Latitude is the current longitude report by GPS.
13  longitude MSB
14  longitude
15  longitude
16  longitude LSB

17 Start_Flag

Shutter start time  (JS)
18 Start Second MSB
19 Start Second
20 Start Second
21 Start Second LSB

22 Start micro second MSB
23 Start micro second
24 Start micro second LSB

25 End flag

Shutter end time  (JS)
26 End Second MSB
27 End Second
28 End Second
29 End Second LSB

30 End micro second MSB
31 End micro second
32 End micro second LSB

33 now flag:  this can be used for the GPS statu indicator   bit[7..4] is the

The now time is the time that of the vertical sync of the CMOS sensor. It does not the precision time of shutter open or close
34 now second MSB
35 now second
36 now second
37 now second LSB

38 now micro second MSB
39 now micro second
40 now micro second LSB

The counter value of two PPS. it should be about 10,000,000. But since the temperature of the crystal. It is not exactly the 10,000,000. You can adjust the VCXO to let it close to it.  And when the PPS signal lost, it will become 10,000,500. When exceed this value, FPGA will generate a second to instead of the GPS PPS signal to avoid the second counter lost one second.
41 count of PPS MSB
42 count of PPS
43 count of PPS LSB

Reference codes:

unsigned int seqNumber=0;
unsigned int seqNumber_old=0;
unsigned char tempNumber=0;
unsigned short width=0;
unsigned short height=0;
unsigned int latitude=0;
unsigned int longitude=0;

unsigned char start_flag=0;
unsigned int  start_sec=0;
unsigned int  start_us=0;

unsigned char end_flag=0;
unsigned int  end_sec=0;
unsigned int  end_us=0;

unsigned char now_flag=0;
unsigned int  now_sec=0;
unsigned int  now_us=0;

unsigned int max_clock=0;

seqNumber=256*256*256*imageHead[0]+256*256*imageHead[1]+256*imageHead[2]+imageHead[3];
tempNumber=imageHead[4];
width=256*imageHead[5]+imageHead[6];
height=256*imageHead[7]+imageHead[8];
latitude= 256*256*256*imageHead[9]+256*256*imageHead[10]+256*imageHead[11]+imageHead[12];
longitude=256*256*256*imageHead[13]+256*256*imageHead[14]+256*imageHead[15]+imageHead[16];

start_flag=imageHead[17];
start_sec=256*256*256*imageHead[18]+256*256*imageHead[19]+256*imageHead[20]+imageHead[21];
start_us =256*256*imageHead[22]+256*imageHead[23]+imageHead[24];

end_flag=imageHead[25];
end_sec=256*256*256*imageHead[26]+256*256*imageHead[27]+256*imageHead[28]+imageHead[29];
end_us =256*256*imageHead[30]+256*imageHead[31]+imageHead[32];

now_flag=imageHead[33];
now_sec=256*256*256*imageHead[34]+256*256*imageHead[35]+256*imageHead[36]+imageHead[37];
now_us =256*256*imageHead[38]+256*imageHead[39]+imageHead[40];
max_clock=256*256*imageHead[41]+256*imageHead[42]+imageHead[43];

decodeJS(start_sec,timeZone,JD,h,m,s);    //this function can convert the JS to the JD time
and maybe you can use the following API(windows or Linux) to convert the JD time to local time.
JulianDateToDateTime(JD)

Void decodeJS(unsigned int JS,double timeZone,double &JD,unsigned char &h,unsigned char &m,unsigned char &s){

unsigned int k;

JD=JS/3600/24+2450000;

k=fmod(JS,3600*24);
h=k/3600;
k=fmod(k,3600);
m=k/60;
k=fmod(k,60);
s=k;

JD=double(JD)+ 0.5+ ((double)(h+timeZone)*3600+(double)m*60+(double)s)/3600/24;

}

//  set the parameters at first
set_GPS_SlaveMode_Parameter(target_sec,target_us,deltaT_sec,deltaT_us,expTime) ;
// switch camera to slave mode
set_GPS_MasterSlave(1);

the target_sec is the JS we defined in our system. The second you get from the image head is just this value.
expTime unit is us. Please note the deltaT must > expTime.

eg. Today is 2017.10.19 0:30 and we can get the JS=695925030
Now we want to let the camera start exposure at 0:40:000000 (10minutes later). The exposure time is 100ms per frame. The interval is 200ms per frame.

target_sec=695925030+600;
target_us=0;
deltaT_sec=0
deltaT_us=200*1000;
expTime=100*1000;

set_GPS_SlaveMode_Parameter(target_sec,target_us,deltaT_sec,deltaT_us,expTime) ;

If want to switch back from the slave mode to master mode ,just call:
set_GPS_MasterSlave(0);