rigol ds1052e pulse width trigger? - Page 1
Forum section: electronics / general

author: ToBeFrank
author_rank: Regular Contributor
timestamp: February 02, 2011, 01:01:35 am
content: I can't get my ds1052e pulse width trigger to worker. It's quite possible (likely) that I just don't understand how it actually works. I'm not trying to diagnose anything. I'm just trying to make sure I understand the functionality.I've created a PCB that logs data from a J1850 bus. In J1850, frames are delimited by a long (>260us) passive period where passive is defined as 0 to 3.5V. I am attempting to see this waveform by setting a pulse trigger of a down pulse that is greater than 200us with sweep set to single. I know for sure that the bus I am monitoring should have a pulse like this as I am receiving messages with my PCB. However, the ds1052e never triggers. Am I doing something wrong or not understanding it correctly? I have the probe at 10x and the ds1052e set for 10x.

author: DaJones
author_rank: Contributor
timestamp: February 02, 2011, 08:34:36 am
content: You've probably already figured this out, but if you can get any kind of capture of the signal ( through proper triggering or otherwise ) you can then examine the signal and determine what the proper trigger voltage level should be and whether the pulse you want to trigger off of is actually present in the signal.So my guess would be that the trigger voltage level was set to a value outside the range of the signal ( or at least that part of the signal that you wanted to trigger off of ).

author: dimlow
author_rank: Frequent Contributor
timestamp: February 02, 2011, 08:36:38 am
content: I have triggered on pulse length on the Rigol, it worked for me. So im sure its not the scope.

author: saturation
author_rank: Super Contributor
timestamp: February 02, 2011, 12:27:56 pm
content: I've use almost all the triggers on the Rigol during my tests, they work as described.To run a test, send a square wave, adjust its duty cycle to say 10-20%, so it looks like a pulse, and view it on auto. Use the Measure functions to get the width of the pulse. Now set the scope to Normal, press 50% [ just in case], and trigger to Pulse, select > icon, and adjust it until it triggers and see if its accurate. Now you can try the 'narrower than', and = too, now AC couple the signal, set the duty cycle to 80-90%, so you have an ~ negative going pulse, and try again so you get familiar with it.

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 02, 2011, 03:16:07 pm
content: set the bus in logging mode so there will be repeating "delimition", set trigger mode to normal or auto, play with the trigger level, see if you can catch the pulse. if cant, i bet there is no pulse at all.

author: wd5gnr
author_rank: Regular Contributor
timestamp: February 02, 2011, 03:39:55 pm
content: See if this helps:http://www.hotsolder.com/2010/04/rigol-ds1000e-pulse-triggering.htmlI wrote it right after I got mine about a year ago. There are other articles on other features, as well.

author: ToBeFrank
author_rank: Regular Contributor
timestamp: February 02, 2011, 05:34:56 pm
content: Thanks guys. I must be doing something wrong because when I set just a voltage trigger, the pulse timings don't match up with the J1850 spec. As I said, I'm receiving messages in my code just fine so I know what I should be seeing on the scope. I'll play with it some more tonight. This is my first scope.

author: ToBeFrank
author_rank: Regular Contributor
timestamp: February 03, 2011, 12:59:02 am
content: Ok, I got it working, sort of. I have no idea what I was doing wrong yesterday as I'm doing the same thing today. I can see the ones and zeroes in the J1850 signal. Very cool! I set voltage trigger high and the pulse width trigger to catch the start of frame pulse (active pulse > 163us) and it successfully triggers. However, it seems I'm stuck on that trigger now. I changed the voltage trigger to low and pulse width trigger to the end of frame pulse (passive pulse > 239us). It triggers, but it's still the start of frame pulse (active pulse > 163us) it's triggering on. Is there something I have to do to get the trigger to change?

author: ToBeFrank
author_rank: Regular Contributor
timestamp: February 03, 2011, 01:08:46 am
content: Never mind, I got it sorted. When the bus is inactive it's passive so I'm seeing really long passive periods. If I zoom way out I can see the messages in between the long passive periods.