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How to give variable input to serail port
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See more: MFCVC++ 
CString itemno;
 
UpdateData(TRUE);
 
itemno.Format("%x",m_itemno);// here m_itemno is integer in range 0 to 100

int  len = itemno.GetLength();
 
if(len == 1)
 
itemno = "0x0" + itemno;
 
if(len == 2)
 
itemno = "0x" + itemno;
 

 
unsigned char data[1] = itemno; // Here I  get problem;

~~~code for CreateFile etc~~~
 
bool retval = WriteFile(hport,data,1,&byteswritten,NULL);
 
//I have to send only 1 byte of data
Now the problem I am facing is that I am unable to convert from CString to
unsigned char data[1].
If for example if m_itemno is 12,then its hexadecimal equivalent is 0x0c
 
if I write unsigned 
char data[1] = {0x0c}
,everything works fine but it is like hardcoding
 
but I want it done programatically so that I can enter any number between o to 100;
 
How to do it ?
Posted 21 Jun '12 - 17:53
adityarao311K
Edited 21 Jun '12 - 18:11
Prasad_Kulkarni103K
v2
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2 solutions

You want to send a binary data byte containing a (decimal) number in the range of 0 to 100 (0x64). Your member variable m_itemno already contains this value. So you might use this:
 
unsigned char data = static_cast<unsigned char>(m_itemno & 0xFF);
bool retval = WriteFile(hport,&data,1,&byteswritten,NULL);
 
Because Intel processors use Little-Endian byte order (least significant byte is stored at lowest address) you may even use:
 
bool retval = WriteFile(hport,&m_itemno,1,&byteswritten,NULL);
  Permalink  
Posted 21 Jun '12 - 21:19
Jochen Arndt27.9K
Edited 21 Jun '12 - 21:42
v2
My problem got solved by using following code snippets
CString Class::IntToHex(int* yourint)
 
{
unsigned char ch[1];
Cstring output;
memcpy(ch,yourint,sizeof(int));
retVal = WriteFile(hPort,ch,1,&byteswritten,NULL);
}
 
CString Class::FloatToHex(float* yourfloat)
{
unsigned char ch2[4];
Cstring output;
 
memcpy(ch2,yourfloat,sizeof(float));
retVal = WriteFile(hPort,ch2,4,&byteswritten,NULL);
}
  Permalink  
Posted 21 Jun '12 - 21:41
adityarao311K
Edited 21 Jun '12 - 21:42
Prasad_Kulkarni103K
v2
Comments
Jochen Arndt - 23 Jun '12 - 4:55
Copying the binary data using memcpy is not necessary. Just pass them as they are to WriteFile: WriteFile(hPort, yourint, 1, &byteswritten, NULL); WriteFile(hPort, yourfloat, sizeof(float), &byteswritten, NULL); Your code contains a buffer overrun in IntToHex when copying 4 bytes (sizeof(int)) to the buffer ch which has a size of 1. The only reason why your code does not crash is the existance of the unused local variable CString output that is overwritten by memcpy.
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