Hello,
both valueof and offsetof operators can be used when defining a FreeMASTER variable object. Each FreeMASTER variable needs to know the address (in target MCU memory space) from where the FreeMASTER could read the required value. Normally, you specify either a direct numeric address or you can use a C-language symbol obtained by reading application’s ELF file. In more advanced way, the TSA-defined symbols can be used – but in any case, such symbol resolves to a single constant numeric address.
In your case, the address of the mbdlt25bf.mbdlt25bfOut->controlword is not statically available in ELF file nor in the TSA because the mbdlt25bfOut is a pointer whose value can be dynamically changed in the application. This is why you need to define the address using the expression:
valueof(mbdlt25bf.mbdlt25bfOut) + offsetof(MinasOutput, controlword)
The valueof operator reads a value of the given FreeMASTER variable (which must exist in FreeMASTER project, it can be sampled “once” as we assume the pointer will not change).
The offsetof operator returns an offset of a given member withing a structure type.
All together, this expression returns an address of mbdlt25bf.mbdlt25bfOut->controlword.
In FreeMASTER, there is a hint describing the operators:
Regards,
Michal
Hello @MichalH,
thank you for your patience and support. I installed the new freemaster version 3.2 so that it's possible to define expression for the variable addresses. My freemaster_cfg.c now looks like this:
FMSTR_TSA_STRUCT(tMbdlt25bf)
FMSTR_TSA_MEMBER(tMbdlt25bf, state, FMSTR_TSA_USERTYPE(MBDLT25BF_STATE))
FMSTR_TSA_MEMBER(tMbdlt25bf, mbdlt25bfOut, FMSTR_TSA_POINTER)
FMSTR_TSA_MEMBER(tMbdlt25bf, mbdlt25bfIn, FMSTR_TSA_POINTER)
FMSTR_TSA_STRUCT(MinasOutput)
FMSTR_TSA_MEMBER(MinasOutput, controlword, FMSTR_TSA_UINT16)
FMSTR_TSA_MEMBER(MinasOutput, operation_mode, FMSTR_TSA_SINT8)
FMSTR_TSA_MEMBER(MinasOutput, target_torque, FMSTR_TSA_SINT16)
FMSTR_TSA_MEMBER(MinasOutput, max_torque, FMSTR_TSA_UINT16)
FMSTR_TSA_MEMBER(MinasOutput, target_position, FMSTR_TSA_SINT32)
FMSTR_TSA_MEMBER(MinasOutput, max_motor_speed, FMSTR_TSA_UINT32)
FMSTR_TSA_MEMBER(MinasOutput, touch_probe_function, FMSTR_TSA_UINT16)
FMSTR_TSA_MEMBER(MinasOutput, target_velocity, FMSTR_TSA_SINT32)
FMSTR_TSA_MEMBER(MinasOutput, position_offset, FMSTR_TSA_SINT32)
FMSTR_TSA_STRUCT(MinasInput)
FMSTR_TSA_MEMBER(MinasInput, error_code, FMSTR_TSA_UINT16)
FMSTR_TSA_MEMBER(MinasInput, statusword, FMSTR_TSA_UINT16)
FMSTR_TSA_MEMBER(MinasInput, operation_mode, FMSTR_TSA_USERTYPE(PDS_OPERATION))
FMSTR_TSA_MEMBER(MinasInput, position_actual_value, FMSTR_TSA_SINT32)
FMSTR_TSA_MEMBER(MinasInput, velocity_actual_value, FMSTR_TSA_SINT32)
FMSTR_TSA_MEMBER(MinasInput, torque_actual_value, FMSTR_TSA_SINT16)
FMSTR_TSA_MEMBER(MinasInput, touch_probe_status, FMSTR_TSA_UINT16)
FMSTR_TSA_MEMBER(MinasInput, touch_probe_posl_pos_value, FMSTR_TSA_SINT32)
FMSTR_TSA_MEMBER(MinasInput, digital_inputs, FMSTR_TSA_UINT32)
One thing that I didn't tell you is that my mbdlt25bf struct is actually an array of struct:
tMbdlt25bf mbdlt25bf[ARRAY_SIZE_MOTORS];
I've one more issue where I'm trying to get the value stored in the variable mbdlt25bf[7].mbdlt25bfOut->controlWord.
The address that I wrote is: valueof(mbdlt25bf[7].mbdlt25bfOut) + offsetof(MinasOutput, controlword), as shown in the picture.
As you can see the value doesn't get updated. Can you advise me?
Thank you again for your cooperation.
Davidino
Hello,
you should first make sure that the FreeMASTER determines the address of mbdlt25bf[7].mbdlt25bfOut member correctly. One way of verifying that would be to examine this member in a debugger or print it to console by the MCU application. In any case, the address of this element should match what FreeMASTER prints in the Variable definition dialog (in my example it prints an address of variable named "var16").
If mbdlt25bf is really an array, the FreeMASTER should understand it and calculate a correct address. Basically, to access the mbdlt25bf[7].mbdlt25bfOut member, the FreeMASTER calculates something like:
mbdlt25bf + 7*sizeof(tMbdlt25bf) + offsetof(tMbdlt25bf, mbdlt25bfOut)
This is a fixed address (not runtime) so FreeMASTER should be able to show it to you in the Variable definition dialog. You should be able to see the address just like I see it for my "var16" above.
When you are sure the above is correct, define a FreeMASTER variable named mbdlt25bf[7].mbdlt25bfOut with the same address specification and size=4 bytes. You should be able to put this variable into a Watch and see the value of the mbdlt25bfOut pointer.
Last, you will be able to define a new FreeMASTER variable named mbdlt25bf[7].mbdlt25bfOut->controlword with address defined by the runtime expression as we discussed earlier:
valueof(mbdlt25bf[7].mbdlt25bfOut) + offsetof(MinasOutput, controlword)
This address is calculated in run-time, because FreeMASTER must first read the mbdlt25bf[7].mbdlt25bfOut variable and add the fixed controlword member offset to the obtained value.
_____________________________
As you can see, dealing with pointers in FreeMASTER is tricky. I would advise again not to declare the mbdlt25bfOut member as a pointer to a MinasOutput structure, but to include the full structure directly. This will enable FreeMASTER to calculate address of mbdlt25bf[7].mbdlt25bfOut.controlword statically and access the controlword member directly.
Regards,
Michal
Hello @MichalH ,
thanks for your detailed answer. I can confirm you that the address stored in mbdlt25bf[7].mbdlt25bfOut is correct (green box in the picture) as it is confirmed in MCUXpresso with the debugger. However, the address valueof(mbdlt25bf[7].mbdlt25bfOut) isn't computed correctly as it shows the question mark (red box in the picture). I don't understand why this happens.
P.S. In case this method doesn't work, I'll create copy of mbdlt25bfOut and mbdlt25bfIn structs and ciclically update the values for the solely purpose of seeing them on Freemaster.
Giving up on struct pointers would affect my program performances.
Thank you again.
Davidino
