Casio Naurtech CETerm Ver.5.5 Scripting Guide - Manual (Page 117)

N AURTECH W EB B ROWSER AND T ERMINAL E MULATION FOR W INDOWS CE AND W INDOWS M OBILE
CETerm Scripting Guide Page 117
5.8.5 Using Single Byte Reads
One pattern which often works well for handling serial port data is to read a
single byte at a time and to accumulate data until a “complete message” can be
processed. Your application and peripheral device wil
l define what a “complete
message” contains, but often messages are terminated by special characters
such as ASCII ETX. When using single-byte reads, you can keep read timeouts
short and optimize responsiveness.
To use this pattern, you would use WaitForEvent with the EV_RXCHAR event
and process the data within your handler. Here is a template for a single byte
read handler
// Serial port data handler
var responseData = [];
var responseState = "PRE_STX";
function MyReadAndProcess( portIndex )
{
var c;
var readTries = 4;
var sp = Device.SerialPort( portIndex );
while (responseState !== "DONE" &&
readTries > 0)
{
c=sp.ReadByte();
if (c < 0)
{
// Read error, try again
OS.Sleep( 20 );
--readTries;
continue;
}
// Reset tries after successful read
readTries = 4;
switch(c)
{
case ASCII_STX:
// Start of response.
responseState = "DATA";
responseData = [];
break;
case ASCII_ETX:
// End of content
responseState = "DONE";
break;