ADLINK PXI-2020/2022 Synchronous Acquisition Card Configuration and Synchronization Guide

SSI_TIMEBASE (PXI_TRIG [0]): The master card outputs its time base clock, while the slave card receives and replaces the internal time base, ensuring that all cards use the exact same sampling clock.

SSI_AD_TRIG (PXI_TRIG [5]): The main card outputs its A/D trigger signal, and the slave card receives it as an external digital trigger.

SSIOADCONV (PXI_TRIG [5] multiplexing): The main card outputs its ADCONV conversion signal, while the slave card receives and replaces the internal conversion signal.

Typical configuration of multi card synchronization (taking 4 PXI-2022 synchronous 64 channel acquisition as an example):

Set card 1 as the SSI_SADCONV master card (outputting ADCONV to PXI_TRIG [5]), and cards 2/3/4 as slave cards (receiving ADCONV from PXI_TRIG [5]);

All cards are configured with the same ScanIntrv value (sampling rate) and DataCnt value;

Card 1 is configured with external digital triggers (such as input from SMB TRG IO), while cards 2/3/4 are configured with trigger sources of PXI_TRIG [5] (i.e. SSI_AD_TRIG);

Start DMA collection for all cards, all cards wait for triggering;

When card 1 receives an external trigger, it generates an ADCONV signal internally and outputs it to PXI_TRIG [5]. All slave cards synchronously receive this signal and start data acquisition.

PXI Star Trigger (PXI_STAR) provides another synchronization method, with propagation delay matching within 1 ns and delay from timing slot to peripheral slot less than 5 ns, achieving more accurate synchronization between modules.

Universal Timer/Counter (GPTC)

The board provides two 32-bit (this series is 32-bit, different from the 16 bit of the 2000 series) general-purpose timers/counters, supporting 8 working modes. The clock source can be selected as internal 20 MHz or external input (up to 10 MHz), and the gate and direction control are flexible:

Mode 1: Simple Gate Control Event Counting

Mode 2: Single cycle measurement (measuring GPTC_GATE signal cycle)

Mode 3: Single pulse width measurement

Mode 4: Software initiates single pulse generation (programmable delay and pulse width)

Mode 5: Edge triggered single pulse generation

Mode 6: Repeatedly trigger single pulse generation (output pulse triggered by each edge)

Mode 7: Edge triggered continuous pulse generation

Mode 8: Software initiates continuous pulse generation (gate control enabled/disabled)

These modes provide hardware level solutions for applications such as speed measurement, PWM generation, pulse counting, etc., without requiring CPU resources.

Calibration and maintenance

PXI-2020/2022 onboard high-precision reference source (ADR02 5V chip, temperature drift ± 3ppm/° C, long-term stability 50ppm/1000Hr), with calibration constants written into the default area of EEPROM at the factory. Users can perform automatic calibration through software after installing the environment (recommended preheating for 15 minutes), without the need for external instruments or manual adjustment of potentiometers. After calibration is completed, the new constant can be stored in one of three user modifiable areas (with date and temperature labels attached) for quick switching under different environmental conditions.

Comparison of accuracy before and after calibration:

Offset error: ≤ ± 0.6mV (gain x 1) before calibration, further improved after calibration

Gain error: ≤ ± 0.02% (gain x 1) before calibration, maintaining high accuracy after calibration

Attention: Before automatic calibration, all external connection cables (especially analog input signal lines) must be removed, as the analog front-end may switch to the internal reference source during the calibration process and may cause voltage changes.

Software Support and Development Ecology

ADLINK provides the D2K-DASK driver library (supporting Windows 98/NT/2000/XP/Vista/7), including DLLs and sample programs, compatible with development environments such as VB, VC++, Delphi, BCB6, etc. This driver library provides complete API functions, covering all functions such as board initialization, channel configuration, trigger settings, DMA transfer, GPTC operation, and calibration. For LabVIEW users, provide DAQ-LabVIEW PnP VI library; For ActiveX/COM environments, provide D2K-OCX controls. All software resources are included in the accompanying All in One DVD.

Development process suggestion:

Call D2K_DeviceOpen to open the device handle;

Call D2K_AI_Config to configure channels, ranges, and gains;

Call D2K_AI_CntConfig to configure ScanIntrv, DataCnt, trigger mode, and trigger source;

Call D2K_AI_CntRead to start DMA continuous acquisition (internal automatic management of Scatter/Gather linked list);

Retrieve data through callback functions or polling;

Call D2K_AI_CntStop to stop the collection.