Convert Small signal pulse to RS-232 signal levels?
Convert Small signal pulse to RS-232 signal levels?
(OP)
I have a USB monitoring device, that once a certain data pattern is found, triggers out a small 4-5V pulse. The pulse is very small, about 400ns. It seems to be too small to be detected on a RS-232 Clear-To-Send (CTS)input pin. I am using a USB RS-232 dongle (Keyspan USA-19HS) as an input to our computer. This USB dongle is used for other measurements too, and I thought it would be convenient to use the CTS pins as sort of a generic "GPIO" for this particular device.
What circuit would I need to put between the pulse generating device and the RS-232 to ensure I get a CTS signal detected?
here is what the pulse looks like on a scope:
Imgur

Web (In case Imgur is blocked)

What circuit would I need to put between the pulse generating device and the RS-232 to ensure I get a CTS signal detected?
here is what the pulse looks like on a scope:
Imgur

Web (In case Imgur is blocked)






RE: Convert Small signal pulse to RS-232 signal levels?
RE: Convert Small signal pulse to RS-232 signal levels?
http://www.ti.com/lit/ds/symlink/max232.pdf
RE: Convert Small signal pulse to RS-232 signal levels?
Good news is that the digital pins on it are good enough to trigger the cts line. It should be able to sense the pulse but i have not gotten that far yet.
What was really amusing was my giddiness in showing the wife the whole setup through to the laptop with a test app flickering hi...low...high..low in a rediculous font. She thinks i am nuts...
RE: Convert Small signal pulse to RS-232 signal levels?
RE: Convert Small signal pulse to RS-232 signal levels?
If the signal were increased to 4 microseconds or even 4 ms, would there be a downside? The upside is clearly that there would be little chance of a noise glitch resulting in either an erroneous trigger, or a missed trigger.
TTFN

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RE: Convert Small signal pulse to RS-232 signal levels?
RE: Convert Small signal pulse to RS-232 signal levels?
I have done some playing and i have struck out a bit I think. I was having all sorts of issues just trying to recapture the pulse again on an o-scope. There seems to be some reliability issue in generating it. The analog input to the Arduino board has a read resolution of 100 microseconds, so I think it is too slow to even catch this pulse. I agree that this signal can hide in the noise very easily, and I was having that issue too. I think the One shot might be the best approach.
Unfortunately I can not modify the source of the pulse (Mercury T2 USB analyzer). I am not sure why they chose the trigger method they did, but oh well.
RE: Convert Small signal pulse to RS-232 signal levels?
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Convert Small signal pulse to RS-232 signal levels?
RE: Convert Small signal pulse to RS-232 signal levels?