pointer envy

[patrick muldoon]

I thought that I knew what I was doing, but I was wrong.

I created a structure for some flags. And all was well, until I decided to save them to EEprom.

struct System_Flags{
int1 Alarm_PT;
int1 Local_SP;
int1 Servo;
int1 extra1;
int1 extra2;
int1 extra3;
int1 extra4;
int1 extra5;
};
struct System_Flags Sys_Flag;

void Toggle_Flag(){
Sys_Flag.Alarm_PT ^=1; /* this works fine */
}

void Write_EE(){
If((char)Sys_Flag != Read_EEprom(15))
Write_EEprom(15,(char)Sys_Flag);
}

Now, this seems to work. But was I right to cast as I did?

At first I thought that Sys_Flag was the base address of the structure, but it's really a variable of type System_Flags, right?

my first try was this, and it went every which way but loose!

void Write_EE(){
char *charptr;

charptr=Sys_Flag;
If(*charptr != Read_EEprom(15))
Write_EEprom(15,*charptr);
}


Would a union have been more elegant?

Would this have fixed the above code?
charptr=&Sys_Flag;

I'm just looking for some assurance that i haven't created some kind of pointer time-bomb that'll come back to haunt me a few revisions from now. Long after I would've suspected this little enhancement.

So if one of you could stop laughing long enough to point me (yes, I said POINT me) in the right direction, I'll promise never to de-reference in public again....today.
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This message was ported from CCS's old forum
Original Post ID: 8825

[Dale Herman]

No problem woth your code. Here was my solution:


union{
struct {
short motion_complete:1; // set if a profiled motion completed according to moton_complete_mode
short position_wrap:1; // set if position wraps around in either direction
short tracking_error:1; // set if abs(commanded (profiled) position - actual position) > psition_tracking_limit
short in_positive_limit:1; // set if positive move went into limit (must be using limits)
short in_negative_limit:1;
short instruction_error:1; // illegal instruction or parameter
short captured:1; // set if the homing capture has occurred (can use limit, home, or index)
short res7:1;
} bits;
int8 all_bits;
} servo_event_status;
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This message was ported from CCS's old forum
Original Post ID: 8826

[patrick muldoon]

I like...
Thanks
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This message was ported from CCS's old forum
Original Post ID: 8827

[Neutone]

You could simplify a lot like this for readability and functionality

int8 System_Flags;
#bit Alarm_PT = System_Flags.0
#bit Local_SP = System_Flags.1
#bit Servo = System_Flags.2
#bit extra1 = System_Flags.3
#bit extra2 = System_Flags.4
#bit extra3 = System_Flags.5
#bit extra4 = System_Flags.6
#bit extra5 = System_Flags.7

Then just save the int8 System_Flags to EEPROM and use the flags directly in code rather than using a function. You also have the option to #Locate System_Flags in the bank that will cause the least number of bank switches.

to me
Sys_Flag.Alarm_PT ^=1
is not as elegant or clean as
Alarm_PT ^=1
___________________________
This message was ported from CCS's old forum
Original Post ID: 8865

[patrick muldoon]

The #bit is something i've never played with before, thanks for the suggestion. Now that I know how to use it, I will.

I do switch my bits in code (within larger functions). I just showed a Readers Digest Condensed version of the usage to save everyone from having to sift thru my whole function.

:=You could simplify a lot like this for readability and functionality
:=
:=int8 System_Flags;
:=#bit Alarm_PT = System_Flags.0
:=#bit Local_SP = System_Flags.1
:=#bit Servo = System_Flags.2
:=#bit extra1 = System_Flags.3
:=#bit extra2 = System_Flags.4
:=#bit extra3 = System_Flags.5
:=#bit extra4 = System_Flags.6
:=#bit extra5 = System_Flags.7
:=
:=Then just save the int8 System_Flags to EEPROM and use the flags directly in code rather than using a function. You also have the option to #Locate System_Flags in the bank that will cause the least number of bank switches.
:=
:=to me
:=Sys_Flag.Alarm_PT ^=1
:=is not as elegant or clean as
:=Alarm_PT ^=1
:=
___________________________
This message was ported from CCS's old forum
Original Post ID: 8900