Daqarta for DOS Contents



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Daqarta for DOS
Data AcQuisition And Real-Time Analysis
Shareware for Legacy Systems
(Use Daqarta for Windows with modern systems)
[STIM3 Output Waveforms (14K image)]

The above image shows an example of the complex stimulus generation capabilities possible using the STIM3.GEN module with a lab-type data acquistion board, including the inexpensive DAS8JR with dual DACs (Computer Boards model CIO-DAS08/Jr-A0, or CyberResearch model CYDAS 8JRAO, about $150). The blue traces show the output waveforms generated by the STIM3 module, while the yellow center trace shows a selected output connected to the ADC input.

The newer STIM3A.GEN Advanced Stimulus Signal Generator can do everything that STIM3 can do, plus a lot more... and it can create dynamically-changing real-time signals. It's also a lot easier to use.

The top blue trace shows a combination of 4 different tone bursts on DAC0, while below it a continuous tone is generated from DAC1. From the bottom up are separate traces for Digital Output bits 0 through 7.

SB16-family sound cards can produce similar signals from the DACs, but they have no digital output capability. (Actually, no sound cards have independent digital outputs, as used here. Some cards have "digital outputs" that are digital versions of the DAC signals, but those are not supported by Daqarta.)

The control menu shows the settings for the A component of the DAC0 output, which in this case is the first tone burst in the series (Start = 0). Each of the four components can be adjusted independently, though the Levels of any overlapping components may need to be reduced to keep the total within limits. Sequences longer than the screen are allowed, and may be viewed via trigger delay. The individual components are here combined into a single presentation, but they may also be used in alternating combinations (components A + B on the first sweep followed by C + D on the next, or 4 separate sweeps).

The DAC1 output shown here is a continuous tone, although it also supports up to 4 independent components just like DAC0. To get a continuous output, Daqarta must be in RTime mode... in Sequential mode there would be gaps between sweeps. The STIM3 module provides special controls to insure that continuous tones will repeat splice-free, and to lock to spectral lines, if desired.

The 8 digital outputs are all individually adjustable. Each allows control over pulse onset delay, high duration, low duration, and polarity, as well as number of repetitions of this pattern to form a pulse train. The overall pulse train may also have an independent onset delay. As with the DACs, the digital outputs may have two or four different alternating combinations, but here each may have its own independent set of 8 independent outputs.

This example was actually generated with the DEMO.ADC driver, which is the default "board" driver in the DQA.CFG configuration file when Daqarta is downloaded. This allows easy experimentation and planning without a real board. When STIM3 is active, its outputs are "wired" to separate input channels selectable from the DEMO Board Control menu, including a separate channel for each DAC and for each digital output bit.

With a real board, Daqarta allows the output sample rate to be FASTER than the acquisition rate by an Oversampling Factor. For the DAS8JR board mentioned earlier, the ADC is limited to a 40 kHz sample rate... but the DACs can run up to at least 150 kHz, and the digital outputs up to 200 kHz. The exact Factor allowed depends upon your board and the speed of your system, but even on a 386DX-40 the DAS8JR can acquire data at its 40 kHz limit while pumping out sample-synchronous independent tone burst patterns on both DAC outputs at 120 kHz EACH in Sequential mode. For continuous outputs in RTime mode, the Factor will be less on slow machines, due to the display update overhead. On the above system with the ADC sampling rate reduced to 20 kHz, both DACs can run at 60 kHz, or one DAC at 80 kHz.

Note that STIM3 only works with lab-type boards, or the SB16-family sound cards. However, the ESS and older 8-bit cards can use their internal OPL2 or OPL3 synthesizers to generate independent Left and Right outputs. None of the sound cards support STIM3 digital outputs.


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