PostThreadMessage with a ThreadID is not reaching the destination

See more:

eVC4.0

C++

MFC

eVC

Hi,

My embedded application is displaying some real time values and some scrolling text.
I am using a CWinThread class to poll my comms port and get the values, and the main UI thread is managing the scrolling.

I am trying to poll at specific intervals, and have tried to use a timer, but this gets gobbled up by the main UI class and doesn't reach the destination unless I specifically include the main UI HWND, which then causes a delay in the main UI update.

So, I chose to use PostThreadMessage in my comms thread to run my timer, but even using the threadID acquired at thread creation, my message never reaches the destination.
I have used IMPLEMENTM and DECLARE _DYNAMIC, and have declared my message maps

IMPLEMENT_DYNAMIC(CMyThread, CWinThread)

BEGIN_MESSAGE_MAP(CMyThread, CWinThread)
    //ON_WM_TIMER ( )
    ON_MESSAGE(WM_APP+15, OnTimer)
END_MESSAGE_MAP()

afx_msg void CADCValuesThread::OnTimer(UINT nIDEvent)
{
    readComms();
}

void readComms()
{
    //read my comms port
    ::PostThreadMessage(m_dwThreadID, WM_APP+15, 0, 0);
}

All to no avail.

Any help as to why my message is not reaching my thread, even though the thread is happily running?

Thanks

Tony