Read
- Updated2025-07-30
- 3 minute(s) read
Reads an element from a Stream channel. The endpoint waits if the channel is empty.

Inputs/Outputs
timeout in ms (-1)
—
timeout in ms is the time, in milliseconds, that this endpoint has to read the elements from the channel. The default value is -1, which means there is no time limit.
channel
—
channel is the channel wire that connects this endpoint to a writer endpoint.
timed out?
—
timed out? returns TRUE if the amount of time specified by timeout in ms elapses before the endpoint reads the data specified in element from the channel. If timed out? is TRUE, element valid? and last element? will be FALSE.
element valid?
—
element valid? returns TRUE if the element was read successfully. This output returns FALSE if a timeout occurs, if the channel closes without a valid last element, or if the channel aborts.
element
—
element returns the data that this endpoint reads from the channel. This output returns the default value of the transmission data type if a timeout occurs, if the channel closes without a valid last element, or if the channel aborts.
last element?
—
last element? returns whether this is the last element that the endpoint reads from the channel. last element? can be TRUE even if element valid? is FALSE, which means that the last element was already written to the channel during the previous iteration or the channel closes without a valid last element. This output returns FALSE if a timeout occurs or if the channel aborts.
count
—
count returns the number of elements in the channel after this endpoint updates the channel. Use this output to monitor the relative writing and reading speed of the channel endpoints and make adjustments, if necessary. |
FPGA Module Details
The following details apply when you use this object in an FPGA VI.
| Single-Cycle Timed Loop | Not supported. |
| Usage | For arrays, this endpoint supports only fixed-sized one-dimensional arrays of supported data types. This endpoint does not support variable-sized arrays even if the array resolves to a single size at compile time. This endpoint does not support LabVIEW classes. If you use this endpoint with the single-precision floating-point data type, refer to the following topics for resource use, latency, and single-cycle Timed Loop support implications. |
| Resources | This endpoint shares resources with the writer endpoint used together in the channel instance. The writer endpoint requires FPGA resources proportional to the number you specified in size. |
| Notes | A channel terminal of a non-reentrant subVI can be connected to only one channel. If a non-reentrant subVI is called from multiple locations, the channel wires connected to a given terminal must resolve to the same channel at compile time. |
timeout in ms (-1)
—
channel
—
timed out?
—
element
—
count
—