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GetCommState failed with error 87.

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uvbaz

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Apr 14, 2008, 8:59:56 AM4/14/08
to
Hi,

i'm trying to set the serial port.(XP SP2, Visual Studio 2005). I use
the example code from MSDN "configuring a communications resource".

CreateFile pass through, however GetCommState return 0.With
GetLastError(), i get the error number 87, which means
"ERROR_INVALID_PARAMETER The parameter is incorrect. "
I'm sure the serial port works, because i can use another program to
read/write through it.

thx
Cheng

Scott McPhillips [MVP]

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Apr 14, 2008, 11:01:40 AM4/14/08
to
"uvbaz" <uv...@stud.uni-karlsruhe.de> wrote in message
news:ec8b47a1-6f67-48ec...@a9g2000prl.googlegroups.com...


Error 87 usually means you have made a simple programming mistake with the
parameters. Can you show the relevant lines of the code? It is very hard
to guess what is wrong if you do not show some code.

--
Scott McPhillips [VC++ MVP]

uvbaz

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Apr 15, 2008, 4:08:30 AM4/15/08
to
On 14 Apr., 17:01, "Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
wrote:

Sorry, i forgot to paste them.

#include <windows.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
DCB dcb;
HANDLE hCom;
BOOL fSuccess;
char *pcCommPort = "COM1";

hCom = CreateFile( pcCommPort,
GENERIC_READ | GENERIC_WRITE,
0, // must be opened with exclusive-access
NULL, // no security attributes
OPEN_EXISTING, // must use OPEN_EXISTING
0, // not overlapped I/O
NULL // hTemplate must be NULL for comm devices
);

if (hCom == INVALID_HANDLE_VALUE)
{
// Handle the error.
printf ("CreateFile failed with error %d.\n", GetLastError());
return (1);
}

// Build on the current configuration, and skip setting the size
// of the input and output buffers with SetupComm.

fSuccess = GetCommState(hCom, &dcb);

if (!fSuccess)
{
// Handle the error.
printf ("GetCommState failed with error %d.\n", GetLastError());
return (2);
}

// Fill in DCB: 57,600 bps, 8 data bits, no parity, and 1 stop bit.

dcb.BaudRate = CBR_57600; // set the baud rate
dcb.ByteSize = 8; // data size, xmit, and rcv
dcb.Parity = NOPARITY; // no parity bit
dcb.StopBits = ONESTOPBIT; // one stop bit

fSuccess = SetCommState(hCom, &dcb);

if (!fSuccess)
{
// Handle the error.
printf ("SetCommState failed with error %d.\n", GetLastError());
return (3);
}

printf ("Serial port %s successfully reconfigured.\n", pcCommPort);
return (0);
}

Check Abdoul

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Apr 16, 2008, 2:23:35 AM4/16/08
to
Try
char *pcCommPort = "\\\\.\\COM1"

Cheers
Check Abdoul
---------------------


"uvbaz" <uv...@stud.uni-karlsruhe.de> wrote in message

news:7fb0be98-eb01-4b8f...@e39g2000hsf.googlegroups.com...

Anthony Wieser

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Apr 16, 2008, 3:32:12 AM4/16/08
to
>
> int main(int argc, char *argv[])
> {
> DCB dcb;
> HANDLE hCom;
> BOOL fSuccess;
> char *pcCommPort = "COM1";
>
<SNIP>

>
> fSuccess = GetCommState(hCom, &dcb);
>
> if (!fSuccess)
> {


You haven't set dcb.DCBlength = sizeof(dcb), so it will fail, as it doesn't
know what size the strucure is.

Anthony Wieser
Wieser Software Ltd

Ian Semmel

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Apr 16, 2008, 3:03:40 PM4/16/08
to
Try putting a security attributes parameter in your create file

m_securityAttributes.nLength = sizeof ( SECURITY_ATTRIBUTES );
m_securityAttributes.lpSecurityDescriptor = 0;
m_securityAttributes.bInheritHandle = true;

Don't know if it will change anything, but that is what I do. Your code
appears OK.

"uvbaz" <uv...@stud.uni-karlsruhe.de> wrote in message

news:7fb0be98-eb01-4b8f...@e39g2000hsf.googlegroups.com:

Joseph M. Newcomer

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Apr 20, 2008, 7:41:30 PM4/20/08
to
I presume there was some actual code that caused this error. How are we expected to offer
advice if you don't show the code that failed?
joe

Joseph M. Newcomer [MVP]
email: newc...@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm

Joseph M. Newcomer

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Apr 20, 2008, 7:47:39 PM4/20/08
to
See below...

On Tue, 15 Apr 2008 01:08:30 -0700 (PDT), uvbaz <uv...@stud.uni-karlsruhe.de> wrote:

>On 14 Apr., 17:01, "Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
>wrote:
>> "uvbaz" <uv...@stud.uni-karlsruhe.de> wrote in message
>>
>> news:ec8b47a1-6f67-48ec...@a9g2000prl.googlegroups.com...
>>
>> > Hi,
>>
>> > i'm trying to set the serial port.(XP SP2, Visual Studio 2005). I use
>> > the example code from MSDN "configuring a communications resource".
>>
>> > CreateFile pass through, however GetCommState return 0.With
>> > GetLastError(), i get the error number 87, which means
>> > "ERROR_INVALID_PARAMETER The parameter is incorrect. "
>> > I'm sure the serial port works, because i can use another program to
>> > read/write through it.
>>
>> Error 87 usually means you have made a simple programming mistake with the
>> parameters. Can you show the relevant lines of the code? It is very hard
>> to guess what is wrong if you do not show some code.
>>
>> --
>> Scott McPhillips [VC++ MVP]
>
>Sorry, i forgot to paste them.
>
>#include <windows.h>
>#include <stdio.h>
>
>int main(int argc, char *argv[])

****
int _tmain(int argc _TCHAR * argv[])
****


>{
> DCB dcb;
> HANDLE hCom;
> BOOL fSuccess;
> char *pcCommPort = "COM1";

****
First, why are you using an obsolete data type like 'char'? Why are you declaring a
variable at all?

The correct code would at the very least be
LPTSTR CommPort = _T("COM1");
but that is not really general; the correct name is actually
_T("\\\\.\\COM1")
because the string you use is only good for COM1..COM9, and fails utterly with COM10.
****


>
> hCom = CreateFile( pcCommPort,
> GENERIC_READ | GENERIC_WRITE,
> 0, // must be opened with exclusive-access
> NULL, // no security attributes
> OPEN_EXISTING, // must use OPEN_EXISTING
> 0, // not overlapped I/O

****
Which is only one of about a dozen possible values you could use here; why single out
FILE_FLAG_OVERLAPPED as being the only flag of meaning?
****


> NULL // hTemplate must be NULL for comm devices
> );
>
> if (hCom == INVALID_HANDLE_VALUE)
> {
> // Handle the error.
> printf ("CreateFile failed with error %d.\n", GetLastError());
> return (1);
> }
>
> // Build on the current configuration, and skip setting the size
> // of the input and output buffers with SetupComm.
>
> fSuccess = GetCommState(hCom, &dcb);

*****
Did you actually READ THE DOCUMENTATION about DCB? Error 87 is EXACTLY the correct
response; you failed to initialize the first element, the DCBlength field. This could be
done by writing
DCB dcb = { sizeof(DCB) };
or by explicitly assigning the lenght. The error code is correct; you provided an invalid
parameter!
joe
*****


>
> if (!fSuccess)
> {
> // Handle the error.
> printf ("GetCommState failed with error %d.\n", GetLastError());
> return (2);
> }
>
> // Fill in DCB: 57,600 bps, 8 data bits, no parity, and 1 stop bit.
>
> dcb.BaudRate = CBR_57600; // set the baud rate
> dcb.ByteSize = 8; // data size, xmit, and rcv
> dcb.Parity = NOPARITY; // no parity bit
> dcb.StopBits = ONESTOPBIT; // one stop bit
>
> fSuccess = SetCommState(hCom, &dcb);
>
> if (!fSuccess)
> {
> // Handle the error.
> printf ("SetCommState failed with error %d.\n", GetLastError());
> return (3);
> }
>
> printf ("Serial port %s successfully reconfigured.\n", pcCommPort);
> return (0);
>}

francois delamotte

unread,
Jan 23, 2012, 7:01:20 AM1/23/12
to
i am using the same code as cheng. Even with the dcb.DCBLENGTH=sizeof(DCB) the program returns error 87. Are there any other possible causes?

> On Monday, April 14, 2008 11:01 AM Scott McPhillips [MVP] wrote:

> "uvbaz" <uv...@stud.uni-karlsruhe.de> wrote in message
> news:ec8b47a1-6f67-48ec...@a9g2000prl.googlegroups.com...
>
>
> Error 87 usually means you have made a simple programming mistake with the
> parameters. Can you show the relevant lines of the code? It is very hard
> to guess what is wrong if you do not show some code.
>
> --
> Scott McPhillips [VC++ MVP]


>> On Wednesday, April 16, 2008 2:23 AM Check Abdoul wrote:

>> Try
>> char *pcCommPort = "\\\\.\\COM1"
>>
>> Cheers
>> Check Abdoul
>> ---------------------


>>> On Wednesday, April 16, 2008 3:32 AM Anthony Wieser wrote:

>>> <SNIP>
>>>
>>>
>>> You have not set dcb.DCBlength = sizeof(dcb), so it will fail, as it does not
>>> know what size the strucure is.
>>>
>>> Anthony Wieser
>>> Wieser Software Ltd


>>>> On Wednesday, April 16, 2008 9:40 PM uvbaz wrote:

>>>> Hi,
>>>>
>>>> i'm trying to set the serial port.(XP SP2, Visual Studio 2005). I use
>>>> the example code from MSDN "configuring a communications resource".
>>>>
>>>> CreateFile pass through, however GetCommState return 0.With
>>>> GetLastError(), i get the error number 87, which means
>>>> "ERROR_INVALID_PARAMETER The parameter is incorrect. "
>>>> I'm sure the serial port works, because i can use another program to
>>>> read/write through it.
>>>>
>>>> thx
>>>> Cheng


>>>>> On Wednesday, April 16, 2008 9:40 PM uvbaz wrote:

>>>>> On 14 Apr., 17:01, "Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
>>>>> wrote:
>>>>>
>>>>> Sorry, i forgot to paste them.
>>>>>
>>>>>
>>>>> int main(int argc, char *argv[])
>>>>> {
>>>>> DCB dcb;
>>>>> HANDLE hCom;
>>>>> BOOL fSuccess;
>>>>> char *pcCommPort = "COM1";
>>>>>
>>>>> hCom = CreateFile( pcCommPort,
>>>>> GENERIC_READ | GENERIC_WRITE,
>>>>> 0, // must be opened with exclusive-access
>>>>> NULL, // no security attributes
>>>>> OPEN_EXISTING, // must use OPEN_EXISTING
>>>>> 0, // not overlapped I/O
>>>>> NULL // hTemplate must be NULL for comm devices
>>>>> );
>>>>>
>>>>> if (hCom == INVALID_HANDLE_VALUE)
>>>>> {
>>>>> // Handle the error.
>>>>> printf ("CreateFile failed with error %d.\n", GetLastError());
>>>>> return (1);
>>>>> }
>>>>>
>>>>> // Build on the current configuration, and skip setting the size
>>>>> // of the input and output buffers with SetupComm.
>>>>>
>>>>> fSuccess = GetCommState(hCom, &dcb);
>>>>>
>>>>> if (!fSuccess)
>>>>> {
>>>>> // Handle the error.
>>>>> printf ("GetCommState failed with error %d.\n", GetLastError());
>>>>> return (2);
>>>>> }
>>>>>
>>>>> // Fill in DCB: 57,600 bps, 8 data bits, no parity, and 1 stop bit.
>>>>>
>>>>> dcb.BaudRate = CBR_57600; // set the baud rate
>>>>> dcb.ByteSize = 8; // data size, xmit, and rcv
>>>>> dcb.Parity = NOPARITY; // no parity bit
>>>>> dcb.StopBits = ONESTOPBIT; // one stop bit
>>>>>
>>>>> fSuccess = SetCommState(hCom, &dcb);
>>>>>
>>>>> if (!fSuccess)
>>>>> {
>>>>> // Handle the error.
>>>>> printf ("SetCommState failed with error %d.\n", GetLastError());
>>>>> return (3);
>>>>> }
>>>>>
>>>>> printf ("Serial port %s successfully reconfigured.\n", pcCommPort);
>>>>> return (0);
>>>>> }


>>>>>> On Sunday, April 20, 2008 7:41 PM Joseph M. Newcomer wrote:

>>>>>> I presume there was some actual code that caused this error. How are we expected to offer
>>>>>> advice if you don't show the code that failed?
>>>>>> joe
>>>>>>
>>>>>> On Mon, 14 Apr 2008 05:59:56 -0700 (PDT), uvbaz <uv...@stud.uni-karlsruhe.de> wrote:
>>>>>>
>>>>>> Joseph M. Newcomer [MVP]
>>>>>> email: newc...@flounder.com
>>>>>> Web: http://www.flounder.com
>>>>>> MVP Tips: http://www.flounder.com/mvp_tips.htm


>>>>>>> On Sunday, April 20, 2008 7:47 PM Joseph M. Newcomer wrote:

>>>>>>> See below...
>>>>>>> On Tue, 15 Apr 2008 01:08:30 -0700 (PDT), uvbaz <uv...@stud.uni-karlsruhe.de> wrote:
>>>>>>>
>>>>>>> ****
>>>>>>> int _tmain(int argc _TCHAR * argv[])
>>>>>>> ****
>>>>>>> ****
>>>>>>> First, why are you using an obsolete data type like 'char'? Why are you declaring a
>>>>>>> variable at all?
>>>>>>>
>>>>>>> The correct code would at the very least be
>>>>>>> LPTSTR CommPort = _T("COM1");
>>>>>>> but that is not really general; the correct name is actually
>>>>>>> _T("\\\\.\\COM1")
>>>>>>> because the string you use is only good for COM1..COM9, and fails utterly with COM10.
>>>>>>> ****
>>>>>>> ****
>>>>>>> Which is only one of about a dozen possible values you could use here; why single out
>>>>>>> FILE_FLAG_OVERLAPPED as being the only flag of meaning?
>>>>>>> ****
>>>>>>> *****
>>>>>>> Did you actually READ THE DOCUMENTATION about DCB? Error 87 is EXACTLY the correct
>>>>>>> response; you failed to initialize the first element, the DCBlength field. This could be
>>>>>>> done by writing
>>>>>>> DCB dcb = { sizeof(DCB) };
>>>>>>> or by explicitly assigning the lenght. The error code is correct; you provided an invalid
>>>>>>> parameter!
>>>>>>> joe
>>>>>>> *****
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