Dear Chris,
Specifying 'PFI6' as the trigger indeed worked. However, I have a few more questions regarding triggering and routing specific signals:
1. In another part of my application, in addition to the triggered, timed analog output on two channels, I would like to perform ai on a single channel, with both ao and ai being triggered by the same event. Can I specify the same trigger input 'PFI6' for both the ao and ai tasks, i.e., the full definition of the simultaneous ai task would be
status:=DAQmxCreateAIVoltageChan(ExposeAlignTaskHandle, PChar(AIChannel), '',
DAQmx_Val_InputTermCfg_Diff, -Image_input_voltage, Image_input_voltage,
DAQmx_Val_VoltageUnits2_Volts, nil);
status:=DAQmxCfgDigEdgeStartTrig(ExposeAlignTaskHandle, 'PFI6', Trigger_Edge);
2. Timing is critical for my application...immediately after the requisite number of points are sent out by the ao task, it is important for me to send a specific digital line high (DO1). If I wait for the output task to be done and then send the line high, the usual windows latency means that there is a few ms delay, which is not acceptable. The way I have been getting around this is to use the two counters on the board to count the number of transitions of the ao update signal, and when the count reaches the expected output count, to send the digital line high. In traditional NIDAQ, I wired the ao UPDATE signal to CTR0 input, and the CTR0 output, which is set up to send a pulse on reaching TC, to the input of CTR1. In my working traditional NIDAQ code, I routed the signals using SELECT_SIGNAL. My translation of this code into NIDAQmx is given below, but based on your suggestion earlier, I think the routing part is incorrect, i.e., I need to know how to wire the UPDATE output to the CTR0 input, and the CTR0 output to the CTR1 input. I would also like to know if it is possible to reset the count of each counter to 0 without stopping and restarting the task.
Thanks in advance for your help!
(The traditional nidaq code are the statements that are commented out that begin with status=)
procedure Set_timers;
var
CTR0Channel,
CTR1Channel : PChar;
TriggerString,
TerminalString :PChar;
begin
//General purpose counter 0
//This counter is used to count the number of update clicks from the dacs
//First create a task handle
status:=DAQmxCreateTask('', @CTR0TaskHandle);
//Next create a CTR channel to count edges, setting the initial count to 0
StrPCopy(CTR0Channel, BoardIdentifier+'/ctr0');
status:=DAQmxCreateCICountEdgesChan(CTR0TaskHandle,
CTR0Channel, //Counter number
'', //default virtual name to assign
DAQmx_Val_Falling, //count on falling edge
0, //initial count
DAQmx_Val_CountDirection1_CountUp); // count direction
//Reset the counter
//Not sure if the next line is already taken care of above
// status:=GPCTR_Control(deviceNumber, ND_COUNTER_0, ND_RESET);
//Application is simple event counting ************ ALREADY DONE ABOVE !!
// status:=GPCTR_Set_Application(deviceNumber, ND_COUNTER_0, ND_SIMPLE_EVENT_CNT);
//Set the initial count to 0 ************ ALREADY DONE ABOVE !!
// status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_0, ND_INITIAL_COUNT, 0);
//Use the UPDATE* signal from the dacs on the PFI_5 pin
StrPCopy(TriggerString,'/'+BoardIdentifier+'/ao/SampleClock'); //may want to change this to PFI5
StrPCopy(TerminalString, '/'+BoardIdentifier+'Ctr0Source');
status:=DAQmxConnectTerms(TriggerString, TerminalString, DAQmx_Val_DoNotInvertPolarity);
//the lines abopve replaced the lines below
//status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_0, ND_SOURCE,ND_PFI_5);
//ALREADY TAKEN CARE OF ABOVE
// status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_0, ND_SOURCE_POLARITY, ND_HIGH_TO_LOW);
//Output pulses on reaching TC
status:=DAQmxSetExportedCtrOutEventOutputBehavior(CTR0TaskHandle,DAQmx_Val_ExportActions2_Pulse);
//line above replaced the line below
// status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_0, ND_OUTPUT_MODE, ND_PULSE);
//Arm the counter, ready to start when the waveform output starts
//Will do this at the end for both counters
// status:=GPCTR_Control(deviceNumber, ND_COUNTER_0, ND_PROGRAM);
{counter number 1. This counter is hooked up to counter 0, and it counts
how many times the other counter has turned over}
//First create a task handle
status:=DAQmxCreateTask('', @CTR1TaskHandle);
StrPCopy(CTR1Channel, BoardIdentifier+'/ctr1');
status:=DAQmxCreateCICountEdgesChan(CTR1TaskHandle,
CTR1Channel, //Counter number
'', //default virtual name to assign
DAQmx_Val_Rising, //count on falling edge
0, //initial count
DAQmx_Val_CountDirection1_CountUp); // count direction
//Reset the counter
// status:=GPCTR_Control(deviceNumber, ND_COUNTER_1, ND_RESET);
//Application is simple event counting
// status:=GPCTR_Set_Application(deviceNumber, ND_COUNTER_1, ND_SIMPLE_EVENT_CNT);
//Set the initial count to 0
// status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_1, ND_INITIAL_COUNT, 0);
//Use TC output of the first counter
StrPCopy(TriggerString,'/'+BoardIdentifier+'Ctr0Out'); //may want to change this to PFI5
StrPCopy(TerminalString, '/'+BoardIdentifier+'Ctr1Source');
status:=DAQmxConnectTerms(TriggerString, TerminalString, DAQmx_Val_DoNotInvertPolarity);
//The above lines replaced the line below
// status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_1, ND_SOURCE, ND_OTHER_GPCTR_TC);
//Line below is taken care of above by DAQmx_Val_Rising
// status:=GPCTR_Change_Parameter(deviceNumber, ND_COUNTER_1, ND_SOURCE_POLARITY, ND_LOW_TO_HIGH);
//Arm the counter, ready to start when the waveform output starts
// status:=GPCTR_Control(deviceNumber, ND_COUNTER_1, ND_PROGRAM);
//Start both counter tasks
status:=DAQmxStartTask(CTR0TaskHandle);
status:=DAQmxStartTask(CTR1TaskHandle);
end;
