HIGH SPEED DIGITIZE VS. SINGLE VALUE I/O REFERENCE > ADVANCED TECHNIQUES >
There are 3 ways to read/write channels to/from instruNet hardware:
1) High Speed Digitize
The instruNet i2x0 processor collects
data from a specific group of channels at a specific rate. Physically, this "processor" is a microprocessor IC that resides on the i200/i230/i240 controller PCB. This processor moves data into ram buffers,
4bytes per point, in 32bit floating point form. When running in "High Speed Digitize" mode, this processor is running so fast,
that other instruNet activity, from that processor, is blocked (e.g. GetChannelValue_iNet()
and SetChannelValue_iNet() cannot run). In some cases, adding multiple i2x0 cards is necessary,
so that one can do the >1KHz High Speed Digitize on one card, and the slower work on another.
When digitizing at >1Ks/sec/ch, you are running High Speed Digitize.
High Speed Digitize is implemented with the following C subroutines:
DigitizeListOfChannels..() and GetDigitizedSegment..().
2) Medium Speed Digitize
This is similar to High Speed, described above, except that the instruNet i2x0 processor acquires digitize data via internal interrupts, and can therefore be interrupted by GetChannelValue_iNet() and SetChannelValue_iNet() while digitizing. The internal interrupts occur sort of randomly, with plenty of idle time inbetween. This method is used when the sample rate is approximately < 1Ks/sec, and is implemented with the following C subroutines: DigitizeListOfChannels..() and GetDigitizedSegment..().
3) Scalar Read/Write
This method involves reading and writing single values, as needed, via the GetChannelValue_iNet() and SetChannelValue_iNet() routines. These routines run properly, except if a High Speed >1Ks/sec/ch Digitize is currently running, in which case, an error code is returned. The GET_DIGITIZE_STATUS(netNum) C macro returns the current status of a i2x0 card as notDigitizing, digitizingHighSpeed, or digitizingMediumSpeed. For more information on the differences between high speed digitize and single value read/write with DasyLab, please click here.