User manual

RP6 ROBOT SYSTEM - 4. Programming the RP6
C allows us to define pointers to functions and call these functions without pre-defin-
ing the function in the library. Usually a function needs to be defined in our Library at
the time of compilation in order to be callable.
This method allows us to use self-defined functions as so-called “Event Handlers”.
Pressing down a bumper will automatically result in calling a predefined dedicated
function (within 50ms). This special function must be registered as an Event Handler
and will have to provide a specific signature: the function must not return a value and
has no parameter (both return value and parameter must be “void”). Therefore the
function's signature will have to look like: void bumpersStateChanged(void). For exam-
ple you may register the Event Handler at the very beginning of the main function.
Registering the Event Handler can be done with the following function:
void BUMPERS_setStateChangedHandler(void (*bumperHandler)(void))
You do not have to exactly understand this command – to make a long story short
this function expects a pointer to a function as parameter...
We will explain this in a simple example:
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#include "RP6RobotBaseLib.h"
// Our "Event Handler" function for the bumpers.
// This function will be called automatically by the RP6Library:
void bumpersStateChanged(void)
{
writeString_P("\nBumper status changed:\n");
if(bumper_left)
writeString_P(" - Left bumper pressed down!\n");
else
writeString_P(" - Left bumper released!\n");
if(bumper_right)
writeString_P(" - Right bumper pressed down!\n");
else
writeString_P(" - Right bumper released\n");
}
int main(void)
{
initRobotBase();
// Register the Event Handler:
BUMPERS_setStateChangedHandler(bumpersStateChanged);
while(true)
{
task_Bumpers(); // Automatically check bumpers at 50ms intervals
}
return 0;
}
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