Acquiring Data from an NI 9235/9236 (FPGA Interface)

The NI 9235 or NI 9236 has eight analog input channels that are sampled simultaneously at the data rate for which you have configured the module. Use the Start and Stop channels of the NI 9235/9236 to put the module in and out of acquisition mode. In acquisition mode, the NI 9235/9236 can only acquire data. You can use the FPGA I/O Node to read the data from the module. You cannot perform other operations with the NI 9235/9236, such as accessing properties, while the module is in acquisition mode.

Note  You must create FPGA I/O items for the NI 9235/9236 before you can configure the items using the FPGA I/O Node.

Putting the Module in Acquisition Mode

Configure an FPGA I/O Node with the Start channel of the NI 9235/9236. Wire a Boolean constant set to TRUE to the Start input of the FPGA I/O Node to send a synchronization pulse to the module. The module starts acquiring data at the data rate you configure.

Reading Data from the Module

When the module starts acquiring data, you can use an FPGA I/O Node to read data from the module. You can connect the AI output of the FPGA I/O Node to various types of functions, including an FPGA Memory function or an FPGA FIFO function. If you read from multiple channels on the module, place the channels in the same FPGA I/O Node to ensure that the VI reads the data synchronously.

Because the NI 9235/9236 internally acquires data at a specified rate, the FPGA I/O Node does not return data until new data has been acquired by the module. If the NI 9235/9236 did not start acquiring data or stops acquiring data while an FPGA I/O Node is waiting for data from the module, the FPGA I/O Node returns a timeout error.

Exiting Acquisition Mode

Configure an FPGA I/O Node with the Stop channel of the NI 9235/9236. Write a TRUE to the Stop input. The module is no longer in acquisition mode and now you can access NI 9235/9236 properties.

Example

Refer to the NI 9235 Getting Started (FPGA) VI in the labview\examples\CompactRIO\Module Specific\NI 9235\NI 9235 Getting Started directory for an example of reading from the NI 9235.

 Open NI 9235 example

Refer to the NI 9236 Getting Started (FPGA) VI in the labview\examples\CompactRIO\Module Specific\NI 9236\NI 9236 Getting Started directory for an example of reading from the NI 9236.

 Open NI 9236 example