/// <summary>
/// Reads the next sample from the device.
/// </summary>
private void DoSample(string locale, float deadband)
{
if (!m_active)
{
return;
}
// read latest value from device.
ItemValueResult currentValue = m_cache.Read(m_itemID, locale, m_reqType, 0);
// check if value has changed.
bool changed = true;
// always return for error.
if (m_latestValue != null)
{
// compare value to last returned value if sampling has not started yet.
if (m_samples.Count == 0)
{
changed = HasChanged(currentValue, m_latestValue, deadband);
}
// compare to previous sample if sampling has started.
else if (m_bufferEnabled)
{
changed = HasChanged(currentValue, (ItemValueResult)m_samples[m_samples.Count - 1], 0);
}
}
// add changed value to the buffer.
if (changed)
{
// clear buffer.
if (!m_bufferEnabled)
{
m_samples.Clear();
}
// check if buffer length is exceeded.
if (m_samples.Count >= MAX_BUFFER_LENGTH)
{
if (currentValue.ResultID == ResultID.S_OK)
{
currentValue.ResultID = ResultID.Da.S_DATAQUEUEOVERFLOW;
}
m_samples.RemoveAt(0);
m_overflow = true;
}
// add new sample to buffer.
m_samples.Add(currentValue);
}
}
