Using a scope to see one shot information

[Szewczykm]

I've got a Rigol 1052e and I'm trying to troubleshoot a problem I'm having using a serial DTR signal to reset an Atmel 328p (arduino) in order to program it.

Using a FT232R breakout board from Sparkfun, it works fine.

Using my own circuit with an FT232R IC, I can communicate with the chip, but with what seems like all of the same components, I can't get it to program.

I know this looks like a microcontroller question, but really, it's a question about using my scope to analyze what's going on.  Or, finding out if I'm just using the wrong tool for the job.

So far I've used the scope to look a cyclical things like PWM and comparing one output to another.  However, I'm trying to figure out how to capture something over time.

The DTR pulse is a one shot thing.  I want to see how the pulse compares between my circuit and the breakout board.

Any advice on how to capture this one shot pulse?  The next thing to look at would be to see how the pulse is timed with the transmission of data to the chip.

Also, as an aside, any tips on probing a little SSOP chip?  I have those clips you use for DIP packages to make clipping leads to the chip easier, do they make something like that for smaller chips?

Thanks!

Mike

[Matje]

I've got a Rigol 1052e and I'm trying to troubleshoot a problem I'm having using a serial DTR signal to reset an Atmel 328p (arduino) in order to program it.

Using a FT232R breakout board from Sparkfun, it works fine.

Using my own circuit with an FT232R IC, I can communicate with the chip, but with what seems like all of the same components, I can't get it to program.

I know this looks like a microcontroller question, but really, it's a question about using my scope to analyze what's going on.  Or, finding out if I'm just using the wrong tool for the job.

So far I've used the scope to look a cyclical things like PWM and comparing one output to another.  However, I'm trying to figure out how to capture something over time.

The DTR pulse is a one shot thing.  I want to see how the pulse compares between my circuit and the breakout board.

Hmm, you have to capture one, export it as image, waveform or so, then capture the other, export it, then compare using some software - image viewer or what came with the device.

Any advice on how to capture this one shot pulse?  The next thing to look at would be to see how the pulse is timed with the transmission of data to the chip.

Setup the trigger, set the scope to "single mode" (see manual, page 2-38 in my PDF), press "Run" and it should be there. It helps a lot to play around with the scope and all the stuff in the menus before trying something serious...

To see the timing between DTR and the data line use both channels, trigger off of DTR.

Also, as an aside, any tips on probing a little SSOP chip?  I have those clips you use for DIP packages to make clipping leads to the chip easier, do they make something like that for smaller chips?

I think there are such devices, you probably wouldn't like the price tag.

Easiest way would be to temporarily solder a short piece of blank wire to the pin of interest and clip to that.

[alm]

Also, as an aside, any tips on probing a little SSOP chip?  I have those clips you use for DIP packages to make clipping leads to the chip easier, do they make something like that for smaller chips?

They do. As Matje already mentioned, be prepared for the sticker shock. I've seen some of them going for tens of dollars each. Sigrok published a nice comparison (scroll down to 'high-end probes' for the one capable to go down to ~0.5 mm pitch. The TPI ones are somewhat affordable. The Electro-PJP ones (also sold by Pomona) use a non-standard 0.8 mm pin connection, as opposed to the standard 0.025" pins.

[Smokey]

Little pieces of wire wrap style kynar wire soldered to the pads make great clip points.  Everyone should have a spool of that stuff around for mods anyway.