Creating Components Part 2: Implementing MathSender Behavior

In this section

In this section you will edit MathSender.cpp to implement the desired component behavior.

As a reminder, below is the component behavior you are trying to implement in this section of the tutorial.

Component Description

The MathSender is going to be an active component which will receive parameters, send parameters, log events, and send telemetry.

Editing the Do Math Command Handler

The handler DO_MATH_handler is called when the MathSender component receives a DO_MATH command. This handler overrides the corresponding pure virtual function in the auto-generated base class. Fill in the handler so that it looks like this:

// In: MathSender.cpp
void MathSender ::
  DO_MATH_cmdHandler(
      const FwOpcodeType opCode,
      const U32 cmdSeq,
      F32 val1,
      MathOp op,
      F32 val2
  )
{
  this->tlmWrite_VAL1(val1);
  this->tlmWrite_OP(op);
  this->tlmWrite_VAL2(val2);
  this->log_ACTIVITY_LO_COMMAND_RECV(val1, op, val2);
  this->mathOpOut_out(0, val1, op, val2);
  this->cmdResponse_out(opCode, cmdSeq, Fw::CmdResponse::OK);
}

Explanation

The first two arguments to the handler function provide the command opcode and the command sequence number (a unique identifier generated by the command dispatcher). The remaining arguments are supplied when the command is sent, for example, from the F Prime ground data system (GDS). The implementation code does the following:

1. Emit telemetry and events.

2. Invoke the mathOpOut port to request that MathReceiver perform the operation.

3. Send a command response indicating success. The command response goes out on the special port cmdResponseOut.

In F Prime, every execution of a command handler must end by sending a command response. The proper behavior of other framework components (e.g., command dispatcher, command sequencer) depends upon adherence to this rule.

Check the build using:

# In: MathSender
fprime-util build

Editing the Result Handler

The handler mathResultIn_handler is called when the MathReceiver component code returns a result by invoking the mathResultIn port. Again the handler overrides the corresponding pure virtual function in the auto-generated base class. Fill in the handler so that it looks like this:

// In: MathSender.cpp
void MathSender ::
  mathResultIn_handler(
      const NATIVE_INT_TYPE portNum,
      F32 result
  )
{
    this->tlmWrite_RESULT(result);
    this->log_ACTIVITY_HI_RESULT(result);
}

Explanation

The implementation code emits the result on the RESULT telemetry channel and as a RESULT event report.

Check the build using:

# In: MathSender
fprime-util build

Summary

Congratulations, you have completed MathSender! Well… there’s always more to be done, such as error handling, adding more telemetry, creating more events, and generally messing around with what MathSender can do. But for the purposes of getting a deployment working, this component is done!

Next: Creating Components Part 3: Starting the MathReceiver