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Below are the two examples described in the video <insert link here> that shows the parameter and logging framework. They have been re-written to fit outside the QT context so they do not match the video 1:1 but they show the same concept.

Remember that if you use the callbacks for parameters and logging together with QT and the callbacks manipulate objects in the UI then they have to be wrapped using signals. Otherwise you will en up with timing issues that will (at some point) crash the application since UI objects should only be updated but the same thread that draws the objects.

In this example we will add a parameter that will be used to “freeze” the LED update function. This isn't very useful but it shows how to use parameters

First of all we need to add the parameter to the firmware, this is done by using the macros PARAM_GROUP_START, PARAM_ADD and PARAM_GROUP_STOP. In crazyflie-firmware/drivers/src/led.c we insert the following to add a parameter:

#include "param.h"
 
bool ledFreeze = false;
 
PARAM_GROUP_START(led)
PARAM_ADD(PARAM_UINT8, freeze, &ledFreeze)
PARAM_GROUP_STOP(led)

This will add a parameter in the TOC named led.freeze of the type uint8_t.

Now we should use this parameter on the client side. This can either be done by reading or writing the parameter. First we add the code to write the parameter:

# crazyflie is an instance of the Crazyflie class that has been instantiated and connected
crazyflie.param.setParamValue("led.freeze", True)

The parameter-framework relies on the fact that the parameters are changed from the client or that the client polls the value of parameters. If you are interested in logging changes that the Crazyflie does itself then the logging-framework is better. If you are interested in reading a parameter this should be done using a callback that will be called from the framework when the value for the parameter is updated. This happens in two cases:

• When the Crazyflie has connected values for all the parameters in the TOC are fetched
• When the client changes a value for a parameter the new value will be sent back from the Crazyflie

To register for a callback and to implement the callback the following is used:

    crazyflie = Crazyflie()
    crazyflie.param.addParamUpdateCallback("led.freeze", paramUpdateCallback)
 
    def paramUpdateCallback(name, value):
        print "%s has value %s" % (name, value) # This will in our example print: led.freeze has value True

In this example we will add logging for the raw gyro values read from the sensor.

First of all we add the variables to the logging TOC by using the macros LOG_GROUP_START, LOG_ADD and LOG_GROUP_STOP. In our example we edit the file crazyflie-firmware/modules/src/stabalizer.c:

#include "log.h"
// The raw gyro values are stored in the gyro struct
LOG_GROUP_START(gyro)
LOG_ADD(LOG_FLOAT, x, &gyro.x)
LOG_ADD(LOG_FLOAT, y, &gyro.y)
LOG_ADD(LOG_FLOAT, z, &gyro.z)
LOG_GROUP_STOP(gyro)

This will add the variables gyro.x, gyro.y and gyro.z to the logging TOC as floats.

On the client side we now add the log configuration, start the logging and then a callback will be called every 10 ms when data arrives from the Crazyflie:

    # Callback called when the connection is established to the Crazyflie
    def connected(linkURI):
        gyroconf = LogConfig("Gyro", 10)
        gyroconf.addVariable(LogVariable("gyro.x", "float"))
        gyroconf.addVariable(LogVariable("gyro.y", "float"))
        gyroconf.addVariable(LogVariable("gyro.z", "float"))
 
        # crazyflie is an instance of the Crazyflie class that has been instantiated and connected
        gyrolog = crazyflie.log.newLogPacket(gyroconf)
 
        if (gyrolog != None):
            gyrolog.dataReceived.addCallback(gyroData)
            gyrolog.startLogging()
        else:
            print "gyro.x/y/z not found in log TOC"
 
    def gyroData(data):
        print "Gyrodata: x=%.2f, y=%.2f, z=%.2f" % (data["gyro.x"], data["gyro.y"], data["gyro.z"])