viRead
Purpose
Reads data from device or interface synchronously.
C Syntax
ViStatus viRead(ViSession vi, ViPBuf buf, ViUInt32 count, ViPUInt32 retCount)
Visual Basic Syntax
viRead&(ByVal vi&, ByVal buf$, ByVal count&, retCount&)
Resource Classes
GPIB INSTR, GPIB INTFC, GPIB-VXI INSTR, Serial INSTR, TCPIP INSTR, TCPIP SOCKET, USB INSTR, USB RAW, VXI INSTR, VXI SERVANT
Parameters
| Name | Direction | Description |
|---|---|---|
|
vi |
IN |
Unique logical identifier to a session. |
|
buf |
OUT |
Location of a buffer to receive data from device. |
|
count |
IN |
Number of bytes to be read. |
|
retCount |
OUT |
Number of bytes actually transferred. |
Return Values
| Completion Codes | Description |
|---|---|
|
VI_SUCCESS |
The operation completed successfully and the END indicator was received (for interfaces that have END indicators). This completion code is returned regardless of whether the termination character is received or the number of bytes read is equal to count. |
|
VI_SUCCESS_TERM_CHAR |
The specified termination character was read but no END indicator was received. This completion code is returned regardless of whether the number of bytes read is equal to count. |
|
VI_SUCCESS_MAX_CNT |
The number of bytes read is equal to count. No END indicator was received and no termination character was read. |
| Error Codes | Description |
|---|---|
|
VI_ERROR_INV_OBJECT |
The given session reference is invalid. |
|
VI_ERROR_NSUP_OPER |
The given vi does not support this operation. |
|
VI_ERROR_RSRC_LOCKED |
Specified operation could not be performed because the resource identified by vi has been locked for this kind of access. |
|
VI_ERROR_TMO |
Timeout expired before operation completed. |
|
VI_ERROR_RAW_WR_PROT_VIOL |
Violation of raw write protocol occurred during transfer. |
|
VI_ERROR_RAW_RD_PROT_VIOL |
Violation of raw read protocol occurred during transfer. |
|
VI_ERROR_OUTP_PROT_VIOL |
Device reported an output protocol error during transfer. |
|
VI_ERROR_BERR |
Bus error occurred during transfer. |
|
VI_ERROR_INV_SETUP |
Unable to start read operation because setup is invalid (due to attributes being set to an inconsistent state). |
|
VI_ERROR_NCIC |
The interface associated with the given vi is not currently the controller in charge. |
|
VI_ERROR_NLISTENERS |
No-listeners condition is detected (both NRFD and NDAC are unasserted). |
|
VI_ERROR_ASRL_PARITY |
A parity error occurred during transfer. |
|
VI_ERROR_ASRL_FRAMING |
A framing error occurred during transfer. |
|
VI_ERROR_ASRL_OVERRUN |
An overrun error occurred during transfer. A character was not read from the hardware before the next character arrived. |
|
VI_ERROR_IO |
An unknown I/O error occurred during transfer. |
|
VI_ERROR_CONN_LOST |
The I/O connection for the given session has been lost. |
Description
The viRead() operation synchronously transfers data. The data read is to be stored in the buffer represented by buf. This operation returns only when the transfer terminates. Only one synchronous read operation can occur at any one time.
Related Topics