LEGO MINDSTORMS Robots, Руководство пользователя, Страница: 68 / 226

Message()
Use this command to return the last byte of data received on the IR port.
ClearMessage()
This command clears the incoming message. You may want to do this after responding to an incoming message, to avoid responding more than once.
The Display
Although you can't control the display directly in NQC, you can configure it to some degree:
SelectDisplay(expression v)
This command tells the RCX to show the data source represented by
v
on its display. The legal values for
v
are shown in Table 4-6. You can achieve the same results by pressing the View button
on the front of the RCX to show the state of the inputs or outputs, but the
SelectDisplay()
command allow you to do this as part of a program.
Page 71
Table 4-6. Display Values
Value Description
0 System clock
1 View Input 1
2 View Input 2
3 View Input 3
4 View Output A
5 View Output B
6 View Output C
You can set the clock in the RCX using the following macro:
SetWatch(const hours, const minutes)
Use this macro to set the current time of the RCX's clock. Unfortunately, only constant values can be used.
The Datalog
With the default firmware, your RCX supports an interesting option called a datalog. The datalog is simply a list of numbers. You can create a new datalog and put numbers into it. Datalogs can
be uploaded to your PC for analysis or display. The datalog commands are:
CreateDatalog(const size)
This command tells the RCX to make space for the given number of elements. There is only one datalog, so this command will erase any previous datalog.
AddToDatalog(expression v)
This command adds a value to the datalog. It's up to you to keep track of how many values are in the datalog. If you try to add values after the datalog is full, nothing happens.
The following example waits for a touch sensor on input 1 to be pressed. For each press, the value of timer 0 is stored in the datalog, which holds 20 values in this example: