Not capturing anything

Topic: Not capturing anything (Read 4371 times) previous topic - next topic

Not capturing anything

January 31, 2013, 04:11:23 am

Hi all,

I have an open bench logic sniffer v1.0.4 connected to my mac, i am using the software recommended on your website. I have had my logic sniffer for ages, never really used it.

I have a new SHT15 temp sensor that I want to use with an Arduino, I want to write my own code using the datasheet it uses SPI. The problem is when I run the sample code on the Arduino I get the results fine. But the logic sniffer doesn't see anything. I can see the signal on my scope. The software just says channel-0 & channel-1 are just HIGH or LOW the whole time. I have connected the GND connection to the Arduino's GND.

I uploaded a simple sketch which sets a pin HIGH for 50ms then LOW for 50ms and the logic analyser just sees LOW the whole time. I have changed the capture sampling rates, I can see the device metadata no problems Firmware 3.07 protocol 2

Can anyone tell me where I am going wrong.

Also running mountain lion on my iMac

Re: Not capturing anything

Reply #1 – February 01, 2013, 06:25:21 am

What are your capture settings? It could be capturing before the change, 50ms is a long time at 100 or 200MHz.

Another thing to check is the inside/outside channel numbering options, make sure the right one is selected in the client.

Re: Not capturing anything

Reply #2 – February 01, 2013, 09:35:16 am

I have played with the capture settings I will change the Arduino to 5ms on-off and try swapping inside outside settings

Re: Not capturing anything

Reply #3 – February 01, 2013, 09:38:18 am

Changed inside-outside and nothing changed all I see is the channel go HIGH and thats it no change

Re: Not capturing anything

Reply #4 – February 01, 2013, 10:05:40 am

Can you please post a screen shot of your capture settings and trigger settings?

Re: Not capturing anything

Reply #5 – February 02, 2013, 10:58:32 pm

Re: Not capturing anything

Reply #6 – February 03, 2013, 02:01:42 am

I have updated both the pic and the bitstream to see if that would help still nothing.

I have even tried running it on my windows laptop no change

Re: Not capturing anything

Reply #7 – February 03, 2013, 08:17:04 am

The OLS is capturing at 200Mhz, which is 5ns resolution. The sample buffer can only hold 120us (0.12ms) of captures total at that rate. At a 50ms SPI signal toggle rate, you won't see anything.

Try a -much- slower sample rate. 32Khz would yield 750msecs of captures.

The trigger causes it to start capturing the instant channel 0 is high. Perhaps try a trigger that looks for a transition instead (ie 0 ->1) would help?

ie: Set stage 1 to detect 0 on ch0, then stage 2 to detect 1 on ch0. Only check the "Action" flag on stage 2 to start captures.

Cheers!
-- IED

Re: Not capturing anything

Reply #8 – February 03, 2013, 10:33:22 am

Thanks, if i thought about the math behind it I would of worked out I was sampling at a huge rate.

I'm using 50 kHz and I can see the UART signal perfectly.

Thanks heaps, is there always noise on the free channels even with the noise filter turned on? (Not important just wondering)

Re: Not capturing anything

Reply #9 – February 04, 2013, 01:14:32 am

Yes, it's pretty common. The buffer inputs are floating. They need grounding or pulldowns to quiet things. For example, attaching 100K SIP resistor networks to the input header can help. Have fun!
-- IED