National Instruments 320682C XModemReceive

Chapter 5 RS-232 Library

for an acknowledgment before it re-sends the current packet. When LabWindows/CVI plays the

role of receiver, it waits for up to waitPeriod seconds for the next packet after it sends out an

acknowledgment for the current packet. If it does not receive the next packet within delayPeriod

seconds, it re-sends the acknowledgment, and waits again, up to maximum#ofRetries times. The

default value of waitPeriod is 10.0.

packetSize sets the packet size in bytes. Its value must be less than or equal to the input and

queue sizes. The standard XModem protocol defines packet sizes to be 128 or 1024. If you are

using any other size, make sure the two communication parties understand each other. The

default value of packetSize is 128.

Using This Function

For transfers with a large packet size and a low baud rate, a large delay period is recommended.

XModemReceive

int result = XModemReceive (int COMPort, char fileName[]);

Purpose

Receives packets of information over the com port specified by COMPort and writes the packets

to the specified file.

Parameters

Input COMPort integer Range 1 through 32.

fileName string Contains the pathname.

Return Value

result integer Result of the XModem receive

operation.

<0 Failure.

0Success.

Using This Function

This function uses the XModem file transfer protocol. The transmitter must also follow this

protocol for this function to work properly.

The Xmodem protocol requires that the sender and receiver agree on the error checking protocol.

This agreement is negotiated at the beginning of the transfer, and can cause a significant delay.