Enable GPS message NAV_VELNED using c++

[srp]

Hi i would like to enable the NAV_VELNED message in order to read velocity data from GPS but i’m not able to enable it.
I am trying to use the code provided by Emlid to enable NAV_POSLLH and i’ve done something like this:

int Ublox::enableNAV_VELNED()
{
    unsigned char gps_nav_status[] = {0xb5, 0x62, 0x06, 0x01, 0x12, 0x00, 0x01, 0x12, 0x01, 0x70, 0x2A};
    int gps_nav_status_length = (sizeof(gps_nav_status)/sizeof(*gps_nav_status));
    unsigned char from_gps_data_nav[gps_nav_status_length];

    return SPIdev::transfer(spi_device_name.c_str(), gps_nav_status, from_gps_data_nav, gps_nav_status_length, 200000);
}

I think the the HEX code for the NAV_VELNED is wrong. How can i find the last 2 bytes related to the checksum? Thank you!

[liudmila.slepova]

Hi @srp,

I see that Lars has shared his part of the code with you in the other thread. Please check this out:

Ground Speed and Course from GPS

It’s been a while since this code has been tested, but here is what I last used. int Ublox::enableNAV_VELNED() { unsigned char gps_nav_velned[] = {0xb5, 0x62, 0x06, 0x01, 0x03, 0x00, 0x01, 0x12, 0x01, 0x1E, 0x67}; int gps_nav_velned_length = (sizeof(gps_nav_velned)/sizeof(*gps_nav_velned)); unsigned char from_gps_data_nav[gps_nav_velned_length]; return SPIdev::transfer(spi_device_name.c_str(), gps_nav_velned, from_gps_data_nav, gps_nav_velned_length, 5000000); }

[srp]

Thanks. Unfortunately it doesn’t seem to work for me

[liudmila.slepova]

Oh, I see. I can hardly help with the custom code but hopefully, the additional comments from Lars will help to shed some light on this.