5.2.10 - StreamConfig

Stream mode operates on a table of channels that are scanned at the specified scan rate. Before starting a stream, you need to call this function to configure the table and scan clock. Requires U3 hardware version 1.21 or higher.

Table 5.2.10-1. StreamConfig Command Response

• NumChannels: This is the number of channels you will sample per scan (1-25).
• SamplesPerPacket: Specifies how many samples will be pulled out of the U3 FIFO buffer and returned per data read packet. For faster stream speeds, 25 samples per packet are required for data transfer efficiency. A small number of samples per packet would be desirable for low-latency data retrieval. Note that this parameter is not necessarily the same as the number of channels per scan. Even if only 1 channel is being scanned, SamplesPerPacket will usually be set to 25, so there are usually multiple scans per packet.
• ScanConfig: Has bits to specify the stream base clock and effective resolution.
• ScanInterval: (1-65535) This value divided by the clock frequency defined in the ScanConfig parameter, gives the interval (in seconds) between scans.
• PChannel/NChannel: For each channel, these two parameters specify the positive and negative voltage measurement point. PChannel is 0-7 for FIO0-FIO7, 8-15 for EIO0-EIO15, 30 for temp sensor, 31 for Vreg, or 193-224 for digital/timer/counter channels. NChannel is 0-7 for FIO0-FIO7, 8-15 for EIO0-EIO15, 30 for Vref, or 31 for single-ended. Note that firmware does not support setting the negative channel 199. Instead, specify 31 for single ended measurements. When using the UD driver’s stream functions 199 will be automatically converted to 31 for ease of use.