topic Re: Tasks? in LabVIEW

How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 13:58:26 GMT

In the attached program, there are 6 buttons in a cluster and 1 individual button. These buttons control a bunch of different relays to control power to different components of a single device. Right now the program works in that I can control the 6 buttons, the LED turns on in the board and the power is being transmitted. What I do not understand is how it is doing this. I ran the program with the highlight execution on and at the start of the read from array component, if say I pressed button 6 and hit ok, it reads #6, where did these get defined and labled? and if i wanted to add another button/relay how do i do this? If someone could explain step by step how this is grouping the relays on the board into an array and then controling them I would really appreciate it. Thanks.

Re: How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 14:23:51 GMT

So the "cluster to array" always reads a #6 regardless of which button I press. This is really confusing me.

Re : How does this program group and cluster these button values into an array?

ramses64 — Mon, 14 Jun 2010 14:24:13 GMT

Hi,

So it is easy. The while loop runs :

1rst step, there is an exclusive Or, which make that 2 boolean controls cannot be ON at the same time.

The second step is to write a port. The port is the collection of channels. 8 (depends of your device) channels make a port.

You can write on a port using several methods : writing an array 1D of booleans (the easiest to understand), or you can write a value to the port. The value is exactly the same that writing a 1D array, because the value is the translation of the array in a word. for exemple, if you write (True,True,False, False) on your port, you can write 12d, or 0C, the result will be the same...

Any other question ?

Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 14:31:07 GMT

Yes one more, and not be rude or unappreciative but....huh? So let's say I added in another button, the board has spots for up to 16 relays, how do I assign it a value in the array and figure out which final value is corresponding to the board? If i press button 4, it calculates a 247 and the button turns on, how do I know where to assign these numbers when I want to add in newe buttons?

Re : Re: Re : How does this program group and cluster these button values into an array?

ramses64 — Mon, 14 Jun 2010 14:38:15 GMT

When you press 4, it calculates 247d, so it is 11100011.

I think that when you measure the voltage on the ports, you will recognize these values. Isn't it ?

Re: Re : Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 14:43:21 GMT

What do you mean measure the voltage? How am I supposed to do this? short of stripping a wire or two on the board for a probe I dont see how I can do this.....

Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

ramses64 — Mon, 14 Jun 2010 14:45:56 GMT

What is your device ?

Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 14:49:12 GMT

This is the device:

http://parts.digikey.com/1/parts/760645-mounting-brd-16-pos-w-50-conn-70rck16-hl.html

Ok I can attach a probe somewhere if I take it out of the housing it is in, but what will that tell me?

Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

ramses64 — Mon, 14 Jun 2010 14:54:08 GMT

It is a TTL signal : if the line is on, you should measure a 5V signal, and if the line is off, you should measure a 0V signal.

Betweek the GND and each line, you should recognize the 11110111, which is the translation of your 247d. I think that it reverse the lines of the port, so you should measure only one port at ON, which is the 4th or the 5th, depending on how you're reading.

Re: How does this program group and cluster these button values into an array?

JÞB — Mon, 14 Jun 2010 14:56:08 GMT

The #6 your seeing is the number of elements in the array not a value for the array.

Now for some deeper explainations. From the code it appears that exactly 1 of 6 valves may be used and an additional valve may be in one of two possible states.

When the program is run the cluster of buttons is initiallized to all False. and we enter the outer while loop where a sequence structure starts. In the first frame of the sequence we initiallize a shift register to hold the current value of "Buttons." and this loop runs unthrottled (Add a wait for next ms multiple to this loop to prevent using 100% of the CPU!)

For each iteration the buttons are read and if a change has occured to any value buttons that were previously True are reset to False to prevent opening more than one valve.

When the user presses OK or stop- the current "Buttons" value is passed to the next frame. This frame convertsthe 7 boolean values to a integer where each valve is controlled by a seperate bit of the integer (Isolation is bit 6 and bits 0-5 each control a mixing valve)

Now I'd strongly recommend reworking the DAQmx calls- it is pointless to initiallize the task each time you want to use it- Create the task in the initialzation case and wait until the user exits to destroy the task. And well a sequence structures are frowned on- (there are better ways to do this)

As far as adding a relay- right now the relays are associated to the hardware by their index position in the cluster (element 1 = bit 0 etc....) to add a new valve you would need to decide what bit you would use to drive it and code in that bits' value to write a 0 in that bit. (hint the 40 constant is realy 0x40 right-click>visable items>show radix )

Let me know if you need further elaboration

Re: Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 14:57:06 GMT

How do I recognize this 11110111? and in terms of the program if everything is the same voltage how does the VI know which port is which? If I add one more button to all the clusters it puts out a negative value and then nothing works. I guess I am still asking/confused on how this program works

Re: Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 14:58:58 GMT

<i>to add a new valve you would need to decide what bit you would use to drive it and code in that bits' value to write a 0 in that bit. </i>

I would like more elaboration on this please. I do not know how to code in any of this information let alone where.

Re: Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

JÞB — Mon, 14 Jun 2010 15:31:37 GMT

Ok- I think this explains a bit(or several)

And revised to add new valve

Re: Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 15:38:16 GMT

Thanks Jeff that explains a lot, I have one more question though. The board was set up with this program to start at slot 8, so slot 8 is the "0" in the array. and adding a new button just pushes everything up 1 so isolation valve is now 15 (the last slot), how can I rewrite everything so that it starts at slot 0? and 0 is is 0 in the array?

Re: Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

JÞB — Mon, 14 Jun 2010 16:09:40 GMT

The task!

The task defines the physical channels that are associated with each bit. so if you create a task that has Channels(

Dev1Port0B0

Dev1Port0B1

Dev1Port0B2

Dev1Port0B3

Dev1Port0B4

Dev1Port0B5

Dev1Port0B7

Dev1Port0B6)

would take a 0b10101111 and turn on bits 5 and 7

Re: Re : Re: Re : Re: Re : Re: Re : How does this program group and cluster these button values into an array?

superomario — Mon, 14 Jun 2010 17:29:37 GMT

This is going to sound stupid but, where are you referring to? The task?

Tasks?

JÞB — Mon, 14 Jun 2010 20:35:24 GMT

When you create a DAQmx Task there are many properties that need to be configured. including what physical channels you use. I' modified the create channel vi you have to expose the channel control. It would be a good idea to read the DAQmx help file at:

Re: Tasks?

superomario — Tue, 15 Jun 2010 15:04:26 GMT

Can you tell me what I am looking for in the help? I'm not even sure where to begin with this honestly, most of the stuff you have been saying is kinda going right over my head.

Right now I think the program was set up for 8 lines which is why I can only make 8 slots on the card work. But I still dont get where it is defined for it to start at the 8th slot on the card and not the first. so if I change it to 16 slots, it looks for a spot after the last on the card and then errors since there isnt one.

Re: Tasks?

JÞB — Tue, 15 Jun 2010 15:49:27 GMT

I'd recommend starting with the heading "NI-DAQmx Key Concepts" and read through the entire section!!!

The same section is duplicated in the LabVIEW help file under the heading "Taking Measurements." Seriously, you are going to need to understand DAQ key concepts- and the help file reads better than my typing of the same info.

superomario wrote:
Can you tell me what I am looking for in the help? I'm not even sure where to begin with this honestly, most of the stuff you have been saying is kinda going right over my head.

Right now I think the program was set up for 8 lines which is why I can only make 8 slots on the card work. But I still dont get where it is defined for it to start at the 8th slot on the card and not the first. so if I change it to 16 slots, it looks for a spot after the last on the card and then errors since there isnt one.

Slots? what are slots? "Slots" do not translate into DAQmx entities, attributes, or properties.

Message Edited by Jeff Bohrer on 06-15-2010 10:49 AM

Re: Tasks?

superomario — Wed, 16 Jun 2010 14:57:30 GMT

So I read over the help a lot last night, with much of it going over my head, but I have been using the DAQ assistant to try and make my own Digital out task/connection. This has produced some progress in that I have gotten the first 8 lights to all light up when i hit test. but I am looking at their Hex values and they are identical to the back 8. I'm guessing this isnt a good thing, though instead of having both light up when I push the buttons now still only lights in the back 8 are controllable. The original task only had 8 lines (Dev1/port0/lines 0-7), so i made a new one that goes from port0 0-7 and has port 1 0-7 as i could not figure out how to extend the port0 to have more lines than just the 8. any more guidance would be great!