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Trigger on signal state "low/high" after "X" time
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James |
Hardware logic analyzers have the option to trigger on a logic state being stuck for a certain period of time either low or high.
Currently Logic 2 supports "Pulse Trigger" which you need to specify both the minimum and maximum time before it will trigger.
However, it will not trigger if a signal stays low, or stays high permanently (i.e., beyond the maximum time of the pulse trigger).
This is useful to debug scenarios where a signal may be continuously toggling during a normal state, and would stop toggling or get "stuck" upon a failure condition.
Thus being able to trigger on a signal getting set to one state for too long would be a useful debug feature, that many hardware logic analyzers (Agilent etc) have, and seems very close to the "Pulse" trigger anyway so maybe won't be too much of a leap to implement.
Activity Newest / Oldest
Tim
(#91878)
"Sometimes I need to see what led up to a serial link stopping. If I could trigger on "no transitions for more than Xms" that would be very handy"
Marco
I found a workaround to enable Trigger on "signal stuck/inactive for X time" on Logic2 using the Trigger + Glitch filter feature.
This only works if you know what the signal logic state will be in the "stuck condition", which can be done easily by having your FW toggle a GPIO periodically during normal condition, or just trigger on your bus data lines (if you are monitoring I2C/UART/SPI/etc traffic getting stuck), since you know what the idle logic state will be (if debugging I2C clock stretch bugs, etc..).
Assuming you have a signal S that you don't expect to remain idle High/Low for more than X ms, then you can setup a Rising/Falling edge Trigger on S, with "Glitch filter" enabled for X ms on S. When you start the capture, you'll need to ensure S is Low (if you setup a Rising edge Trigger) or High (if you setup a Falling edge Trigger) -- you can do that easily by moving the signal probe to Low/GND or High/Vdd for at least X ms, then move the signal probe onto signal S within X ms. You'll notice that the Saleae capture will keep the toggling signal static at Low/High (until the Glitch filter fires).
As an example, assume you are monitoring an I2C bus for inactivity or getting stuck, and you expect I2C transactions to occur at a minimum once every 5 seconds. When the bug occurs, I2C transactions will stop and the I2C SCL line will remain high indefinitely.
Here are the Trigger configuration steps:
1. Enable Rising Edge Trigger mode on I2C SCL
2. Enable "Glitch filter" on I2C SCL for 5 s
3. Start the capture
4. Make sure that the I2C SCL (in the Saleae capture) shows the signal as Low (it should since I2C signal is toggling on every transaction and the Glitch filter has not triggered yet); if it's High, just take the signal probe and connect it to GND for 5s+ (you should now see a falling edge in the Saleae capture, which is not firing the Trigger). Then move the signal probe back onto I2C SCL (within 5 s)
6. Now the Trigger will fire if I2C traffic stops for 5s+, as the Glitch filter will mask (to Low) any SCL toggling within 5s, but cause a Rising edge on the filtered signal once toggling stops (indicating signal stuck high) for 5s.
If the logic state in the stuck case for the signal you are trying to probe is not known, the same "Trigger + Glitch filter" can be done by using a separate debug GPIO that is pulsed whenever the other signal is expected to toggle (in IRQ or other runtime execution).
Hope this helps
Sean
Fantastic contribution, Marco, thanks. I can confirm that this works exactly as described and is now saving me a lot of hassle.
Richard
Please, this was requested years ago. And I need it now :)
Tim
discuss.saleae.com/t/question-for-trigger-pattern-i-wanna-capture-low-too-long-pattern/2489/1
"How can I use trigger ‘Low Pulse’ for “Low too long”?
I want to capture when signal is stucked, but It seems only support trigger which must be setup by time range of Low Pulse mode.
Is there other options for?"
Tim
(#83255)
"It would be handy if you can trigger on a pulse NOT within a range.
(As far as I can see, it is now only possible to trigger when a pulse IS in the range, there is no option to invert that logic)
Sometimes you just want to trigger on a non-expected pulse width."
Peter
Only adding the option to invert the logic (i.e. trigger when NOT in range) would already give a lot more freedom.
If this is extended then with the possibility to trigger when it will guaranteed be out of range even if you did not detect the other edge yet will solve most (if not all) of the issues here.
But a simple option to invert the trigger logic is a good start!!
Tim
(#82884)
"We need to trigger the event of our 250Khz signal if it drops out at any time. We have a Saleae Logic Pro 8."
Tim
(#80674)
"I would like to stop the analyzer on a certain event. For example, supposing I have a 1Hz signal on a line. If the signal stops changing, can I set up the analyzer so it stops acquiring"
James
This feature is really useful!
Gabriel
Is there any news on this feature ? I am often chasing down bugs that crash my system after multiple hours and catching a trace is currently neat impossible since I would need to spend hours in front of the Logic 2 software. We were able to mitigate this by using an oscilloscope as a trigger point. This feature would be a major time saver for us.
Tim
This is a feature that is available in Logic 1.x, however, we don't recommend using that version of the software, and we no longer support nor develop for it. In addition, newer revision hardware no longer work on it.
support.saleae.com/logic-software/legacy-software/older-software-releases
Unfortunately, outside of the workaround above, we don't have any updates on this feature request right now.
Tim
(#78087)
"It could be nice to have a new trigger feature. Currently I am using Analyzer I2C and I would like to catch when communication with sensor is stopped throw the interrupt line, could it be possible to add a trigger on pin state low (or high) for more than x ms or sec ?"
Rob
This feature is needed. Please add back, even if just allowing to set n/a as described in the faq:
support.saleae.com/faq/technical-faq/how-to-trigger-on-a-pulse-with-no-maximum-time-limit
Tim
discuss.saleae.com/t/trigger-on-pulse-without-an-end/1168
"Hi. I wanted to know if and when you will re-insert the possibility to trigger on a pulse with a minimum length but without the other edge (in 1.x it was possible by setting the upper range to n/a or something similar). It was really a very useful feature! Thanks in advance."
Ron
With the original Logic software it was possible to trigger on a pulse that with to specific maximum time. This was very useful for example to trigger when a signal stops changing.
This feature was explicitly mentioned on your site:
support.saleae.com/faq/technical-faq/how-to-trigger-on-a-pulse-with-no-maximum-time-limit
Currently I cannot select a "n/a" value for the maximum time so this does not work anymore.
Tim
Merged with: Trigger on a pulse with no maximum time limit
Peter
Hi David,
I'm just a customer so I don't have the full story, but my understanding is that the analyzer uses an FPGA to manage sampling and data conversion so it effectively just sends transitions to the host computer. I'm sure Saleae will set me right if I've got the wrong end of the stick, but they are west coast USA so they won't see this thread until USA Monday.
So yes, my understanding is that even sampling at 500MHz the data rate and data size out of the analyzer will be a function of the total transition rate across all sampled digital channels.
david c
I agree this would be good to have. i have tried to group a parallel bus, and wanted to add it would be nice to also prioritize sampling rates, so that if one signal was an enable strobe, you might want to sample at 10KHz because it transitions once rather than blowing 1/10th of the 550MHz sampling capability if you have 10 signals to watch. Even if there was a high medium low so it isn't infinitely variable, this would be good.
Peter
Saleae run length encodes the digital data so only transitions are recorded for digital signals. The implication is that even at high sampling rates, with little actual activity in the sampled data the data rate is low.
david c
Hi Peter,
So let me get this straight. When I have 5 signals and set the sampling rate to 500MHz, each is not using 100MHz bandwidth of the total sampling capability? It also could be that if the signals are entering an FPGA with a 500MHz fabric speed, then ALL signal edges are sampled at this rate. I am not sure which is in the device. My thought was if I have a strobe with high speed signals like a clock inside it, then I would rather have control over the sampling rate so I could put 250MHz sampling on the clock and maybe 1 MHz sampling rate on the strobe.
Frank
i am confused why this has not been readded? it seems rather easy to allow for a 0 to be left on the maximum input field of trigger width to achive at least the simple configuration of this function! But I also don't know how extensive internal the trigger code would look like then. Currently you can not enter a minimum greater than the maximum, which makes sense but a 0 should be a special case IMHO
Tim
(#61601)
"I am using 2.3.29, and cannot configure for a minimum pulse width like I used to. How should it be done?
I have a signal that I want to trigger if it is low for at least 25 seconds. There is no maximum time limit."
Richard
When my device stops working, I would like to see what happened at the very end. How about a trigger on a signal without any transitions for longer than a specified time?
Tim
Merged with: Trigger on absence of activity
Richard
Hi, We have about 10 saleae Logic8/Logic16, this is a needed feature in the new version of the SW which is otherwise quite great! Thank you!
Tim
(#58890)
Feature Request - trigger on pulse with no maximum end time. Need to catch when a logic signal goes inactive (no switching events for some time).
Mitchell
Thanks for copying this here. This would be a very useful feature for debugging cases where a bus hangs up and there isn't another control/trigger signal available to indicate this otherwise.
Tim
Request via GitHub issue:
"I don't see the option for "n/a" as maximum limit in Logic 2. Is it possible to set up a trigger this way?
github.com/saleae/gitbook-docs/blob/master/faq/technical-faq/how-to-trigger-on-a-pulse-with-no-maximum-time-limit.md"
pwsaleae111
please implement this feature asap, it is really annoying!
Tim
(#58300)
"So I need a function which start the capture after a signals stop to work
or if a signal is no longer change ovver some seconds"
Tim
(#57831)
"Hi I'm using the Version 2.3.17 of Logic. How to set the max duration of a low pulse in the trigger so that it is a "not care"? Before there was a n/a option"
Tom
We desperately need this feature as well. We're trying to hunt down an issue with i2c clock stretching where the stretch exceeds a threshold. I believe Logic 1 has had this feature for some time.
Marcos
How can you define a trigger on pulse width with a certain min. width but no max. limit? I think the tool always asks for a finite max. value. However, there are situations where one is interested in a certain min. value to trigger.
Tim
Merged with: Pulse trigger with no max. time
Peter Jaquiery
Marcos raises an important point here. If there is a set maximum period the trigger can't be generated until that amount of data has been collected after the candidate pulse leading edge. A "Don't care" maximum value allows the trigger to be generated as soon as the minimum pulse period is exceeded.
This could be looked at as a edge trigger with a minimum debounce period.
Phil
I would add my vote that this is an important feature to have. I am trying to track down the source of a system lockup right now, and a certain wire going to a high state for longer than 10 mSec is a sign that things have gone bad.