Maximum Number of Points in the cbAoutScan call

[Fergal Cassidy]

 

int cbAOutScan(int BoardNum, int LowChan, int HighChan, long NumPoints, long *Rate, int Range, int MemHandle, int Options)

 

Using the cbAOutScan call for the USB 1808 and assuming a 100kHZ output rate, channels 0 to 1 and CONTINUOUS option what  is the maximum number of NumPoints that can be loaded.

[DAQman]

Hello,

The count variable is a Long number type, so it is a signed 32 bit number. A negative buffer size make no sense, so the maximum is half that or 2,147,483,647. But ultimately, it will depend on what your system will allow. 

John

 

[Fergal Cassidy]

John

Are you absolutely sure that a USB 1808 has 8M internal memory to allow for a load of 2 outputs x 2,147,483,647 points?

Regards

Fergal

 

[Fergal Cassidy]

John

Sorry that should read 8GB of memory? Is it that the Universal library co-ordinates the transfer and uses 8GB Windows memory and there is no concern for the memory capacity of the USB 1808.

Regards

Fergal

 

[DAQman]

Hi Fergal,

You are correct, the buffer is maintained in the driver. This allows us to use a small hardware buffer and this is true for most of our devices.

For many applications, a large buffer is unnecessary because it can be update during operation. In the following example, the buffer is  update while running. It writes the same data (for simplicity) over-n-over - first updating the low half then the upper half of the buffer depending on the index location.

https://kb.mccdaq.com/KnowledgebaseArticle50719.aspx

Regards,

John