I desire to have an external sync signal (too short a duration) detected by a 6062E board and output a pulse of longer duration as a sync signal that I would be reading on an analog channel along with other sensors on other analog channels. I used example program 2055.zip, STCgeneratesinglepulse, for LW/CVI as my starting point. I modified the sample program so that it is retriggerable instead of just single pulse. This example code uses GPCTR0. The program does work but not as I expected. GPCTR0_OUT has the generated output pulse and programmable duration that I was wanting. GPCTR0_GATE is for the input trigger/sync signal. What I found was that the GATE has a constant +5VDC signal. The problem is that the only trigger that works is an intermittent grounding to the GPCTR0_GATE. I was wanting to work with an external sync signal (short low-high-low signal). I was using the DAQ board's +5VDC power pin to mimic an external trigger. How can I use such a trigger signal to generate the pulse? I have included a stripped down, short version of the revised sample program below and also as an attachment.
#include "nidaqex.h"
/*********************************************************************
* Example program: Based on 2055.zip
* STCgenerateSingleTriggeredPulse.c //changed to retriggerable
*
* Description:
* Generates a retriggerable digital pulse 1 ms LOW and 100 ms HIGH using
* general purpose counter 0 upon a trigger (for devices with the
* DAQ-STC counter/timer)
*
* Pin Connection Information:
* Your digital output pulse will be on the GPCTR0_OUT pin (2 for 6062).
* Connect this output to an analog channel for time syncing w/normal DAQ.
* Connect your digital input trigger pulse to the PFI9/GPCTR0_GATE pin (3 on 6062).
* Connect the ground reference to the 'digital ground' pin (4 or 18 on 6062).
*
* To trigger, connected pin 3 to ground. But, this is not what I want.
* Want trigger to be a LOW-HIGH-LOW. How?
*
* Presence or absence of following line had no effect.
* iStatus = GPCTR_Change_Parameter(iDevice, ulGpctrNum, ND_GATE_POLARITY, ND_NEGATIVE);
*
*********************************************************************
* Used a second computer/DAQ system to monitor.
* Monitoring System connected to DAQ Computer
* ---------------------------------------------- -----------------------
* ACH0 (68) GPCTR0_OUT (2)
* ACH8 (34) jumpered to AIGND (67) DGND (4)
*
* OR
*
* Use Counter on second computer/DAQ system to monitor.
* Monitoring System connected to DAQ Computer
* -------------------------------- -----------------------
* PFI9/GPCTR0_GATE (3) GPCTR0_OUT (2)
* GND GND
*
*********************************************************************/
void main(void)
{
char c; //for testing
i16 iStatus = 0;
i16 iRetVal = 0;
i16 iDevice = 1;
u32 ulGpctrNum = ND_COUNTER_0;
//u32 ulLOWcount = 100; //1ms
//u32 ulHIGHcount = 10000; //100ms
u32 ulLOWcount = 2; //0.02ms
u32 ulHIGHcount = 10; //0.1ms varied for testing
iStatus = GPCTR_Control(iDevice, ulGpctrNum, ND_RESET);
iStatus = GPCTR_Set_Application (iDevice, ulGpctrNum, ND_RETRIG_PULSE_GNR);
iStatus = GPCTR_Change_Parameter(iDevice, ulGpctrNum, ND_SOURCE, ND_INTERNAL_100_KHZ);
//iStatus = GPCTR_Change_Parameter(iDevice, ulGpctrNum, ND_GATE_POLARITY, ND_NEGATIVE);
iStatus = GPCTR_Change_Parameter(iDevice, ulGpctrNum, ND_GATE, ND_PFI_9); //Gate, apply trigger here
iStatus = GPCTR_Change_Parameter(iDevice, ulGpctrNum, ND_COUNT_1,ulLOWcount);
iStatus = GPCTR_Change_Parameter(iDevice, ulGpctrNum, ND_COUNT_2,ulHIGHcount);
/* To output a counter pulse, you must call Select_Signal. */
iStatus = Select_Signal (iDevice, ND_GPCTR0_OUTPUT, ND_GPCTR0_OUTPUT,ND_LOW_TO_HIGH);
iStatus = GPCTR_Control(iDevice, ulGpctrNum, ND_PROGRAM);
//printf("Apply your trigger pulse to PFI9 now.\nThe rising edge will arm and the second falling edge will gate in the value.\n");
c=getchar(); // this simulates normal DAQ.
iStatus = GPCTR_Control(iDevice, ulGpctrNum, ND_RESET);
/* Note that the following Select_Signal call will cause the
output to be high impedance which will most likely bring the logic
level HIGH if there is a pull-up resistor on this pin. (Check your
hardware user manual.) If you do not want this behavior, comment out
the next line. */
//iStatus = Select_Signal(iDevice, ND_GPCTR0_OUTPUT, ND_NONE, ND_DONT_CARE);
return;
}
