[Paparazzi-devel] 回复： Why the rotorcraf t have a lower message frequency from ubloxGPS module?

[QawsQAER]

Thank you for your explanation Mr.Wagter, that really helps!

in sw/airborne/modules/gps/gps_ubx_ucenter.c

404  case 14:

405  UbxSend_CFG_RATE(0x00FA, 0x0001, 0x0000);

If i'm not mistaken, this line of code set the main loop time to 0x00FA ms = 250ms.

I wonder if i can make the loop time shorter to have a higher frequency(e.g,change 0x00FA to 0x00CA = 200) of NAV-SOL message so that the position estimate is more accurate.?(BTW, I'm using ublox Lea-6h).

Also, by checking the document of ublox, I have another problem.

Lea-6H seems to have maximum navigation update rate as 2Hz(http://www.u-blox.com/images/downloads/Product_Docs/LEA-6_DataSheet_%28GPS.G6-HW-09004%29.pdf, page 6, GPS performence), will it cause any contradiction to the main loop set to 4hz?

I'm just a freshman to UAV, so I might be asking stupid question, thank you for your patience anyway.  :) 

------------------

Edward ZILONG HUANG

address@hidden department, Faculty of Engineering, CUHK

http://appsrv.cse.cuhk.edu.hk/~zlhuang2

 

------------------ 原始邮件 ------------------

发件人: "Christophe De Wagter [via Paparazzi]"<[hidden email]>;

发送时间: 2013年7月29日(星期一) 上午6:10

收件人: "Εd1."<[hidden email]>;

主题: Re: Why the rotorcraft have a lower message frequency from ubloxGPS module?

The number is a loop divider, not the frequency. The main loop time is set elsewhere to 250ms. So 1 means 4Hz. And 8 means every 2 seconds as the fixed wings use position not from ECEF in NAVSol but from LLH and only use nav Sol for the accuracy.

On Jul 28, 2013 7:56 PM, "QawsQAER" <[hidden email]> wrote:

Dear Developers:

I notice that in sw/airborne/modules/gps/gps_ubx_ucenter.c,
it configure message to be sent from the GPS module

  391 #if defined FIRMWARE && FIRMWARE == ROTORCRAFT
  392     gps_ubx_ucenter_enable_msg(UBX_NAV_ID, UBX_NAV_SOL_ID, 1);
  393 #else
  394     gps_ubx_ucenter_enable_msg(UBX_NAV_ID, UBX_NAV_SOL_ID, 8);
  395 #endif

What's the reason for rotorcraft to have a lower NAV-SOL message frequency ?
As the measurement frequency is 4hz, can i change
gps_ubx_ucenter_enable_msg(UBX_NAV_ID, UBX_NAV_SOL_ID, 1);
into
gps_ubx_ucenter_enable_msg(UBX_NAV_ID, UBX_NAV_SOL_ID, 4);
?




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