MATLAB REAL-TIME WORKSHOP 7 - TARGET LANGUAGE COMPILER Manuale Utente Scaricare il pdf (Pagina 374)

8 Serial Port I/O

8-54

Example: Using Events and Callbacks

This example uses the M-file callback function instrcallback to display

event-related information to the command line when a bytes-available event or

an output-empty event occurs.

1. Create a serial port object – Create the serial port object s associated with

serial port COM1.

s = serial('COM1');

2. Connect to the device – Connect s to the Tektronix TDS 210 oscilloscope.

Since the default value for the

ReadAsyncMode property is continuous, data is

asynchronously returned to the input buffer as soon as it is available from the

instrument.

fopen(s)

3. Configure properties – Configure s to execute the callback function

instrcallback when a bytes-available event or an output-empty event occurs.

Since

instrcallback requires the serial port object and event information to

be passed as input arguments, the callback function is specified as a function

handle.

s.BytesAvailableFcnMode = 'terminator';

s.BytesAvailableFcn = @instrcallback;

s.OutputEmptyFcn = @instrcallback;

4. Write and read data – Write the RS232? command asynchronously to the

oscilloscope. This command queries the RS-232 settings and returns the baud

rate, the software flow control setting, the hardware flow control setting, the

parity type, and the terminator.

fprintf(s,'RS232?','async')

instrcallback

is called after the RS232? command is sent, and when the

terminator is read. The resulting displays are shown below.

OutputEmpty event occurred at 17:37:21 for the object:

Serial-COM1.

BytesAvailable event occurred at 17:37:21 for the object:

Serial-COM1.

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MATLAB REAL-TIME WORKSHOP 7 - TARGET LANGUAGE COMPILER Manuale Utente Pagina 374