Setting precision to mm

[berbaba]

Hello!

I have been trying to change the precision of the device's reads but have been unsuccessful.

The TFMPlus.h file includes a line (137) with the definition for STANDARD_FORMAT_MM assigned to a certain hexadecimal value. This is next to other commands like SET_FRAME_RATE (with its corresponding hexadecimal value) that are used with the sendCommand() function in the TFMPlus.cpp, but said function works for the following commands: SET_FRAME_RATE SET_BAUD_RATE OBTAIN_FIRMWARE_VERSION SYSTEM_RESET RESTORE_FACTORY_SETTINGS SAVE_SETTINGS and the change of format is not implemented here.

I would like to be able to fix this but I don't have enough knowledge and the warning of causing the device to be unresponsive prevents me from changing some things.

As far as I understand it should follow the commented steps in the function:

bool TFMPlus::sendCommand( uint32_t cmnd, uint32_t param)
{
   // Step 1 - Build the command data to send to the device

 if( cmnd == STANDARD_FORMAT_MM)     // If the command is Standard Format MM...
    {    
              memcpy( &cmndData[ 3], &param, X);     // add the X byte Standard Format parameter. 
// 3 is the array position for the example I copied (SET_FRAME_RATE)
// but maybe in this case is different. I don't know X either.
    }
 
     // Step 2 - Send the command data array to the device

     // Step 3 - Get command reply data back from the device.

    // Step 4 - Perform a checksum test.

    // Step 5 - Interpret different command responses.

    // Step 6 - Set READY status and go home

}

I assume steps 2, 4 and 6 should stay the same, but don't know if this command generates a reply or not (steps 3 and 5). At the moment there is not much more I can do.

Anyway, thank you for the library!

[budryerson]

Berbaba,

The two formatting commands do not require a parameter, so the param byte is set to 0. In the included example sketch, the command would look like this:

tfmP.sendCommand( STANDARD_FORMAT_MM, 0))

Both formatting commands return only an echo of the command. They do not return a pass/fail bit or other useful information. Therefor, the library only examines the reply for a correct checksum byte.

// The library 'sendCommand( cmnd, param)' function
// defines a command (cmnd) in the the following format:
// 0x     00       00       00       00
//     one byte  command  command   reply
//     payload   number   length    length
                                                 
#define    SET_FRAME_RATE             0x00030606   // These commands each return
#define    SET_BAUD_RATE              0x00060808   // an echo of the command
#define    STANDARD_FORMAT_CM         0x01050505   //           "
#define    PIXHAWK_FORMAT             0x02050505   //           "
#define    STANDARD_FORMAT_MM         0x06050505   //           "

Please bear in mind that what you call "precision" is only how the data is formatted. The accuracy (±5cm) and resolution (±5mm) of the device do not change.

I hope this is helpful. I'm not sure of your question, so please let me know if there is anything more I can add.

Bud Ryerson San Francisco

[berbaba]

Thank you very much for replying so quick! I changed it and worked as expected, the measures had an extra digit for milimetres, just needed to change the printf as having an extra cipher wouldn't show measures with 5 digits (measures over 10 m = 1000 cm = 10000 mm) and the text printing "mm" instead of "cm". I will put this as a pull request in case you want to add it to the library (more as a concept than an a good code). Again thank you.

Bernat Valencia