Sniffing the Arduino Serial with a DSO

Other Hardware General Electronics
1

Dear community,

I ordered an DSO QUAD to learn a bit about scope usage and see my electrical experiments in wave forms for further analysis (I know that this is a toy... no comments about that please ;)).

I tried to sniff a serial message with the scope without any luck (actually tried what this guy did in his digital test: DSO Quad - Hosentaschenoszilloskop, I you do not speak German scroll to the middle of the page for a scope screenshot)

Yo can see my connections in the attached picture. Prope connected to TX, Pin 1

Im running this code on the Arduino:

#include <Serial.h>

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println("HELLO");
  delay(1000);
}

My scope settings are:

Trigger: Falling Edge for Channel D
Trigger Mode: Single
Channel: (Digital) D

But my scope does not trigger at all as it does in the test from the link above.

Any ideas what Im doing wrong? I the DSO broken?

Thanks in advance!

Regards!

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2

the ground of the probe is correctly connected to the ground of the arduino?
you are working with the D channel but it seems to be disabled "--" on the screen of the scope
the trig voltage is lower than 5v?

3

Establish the scope works first.

Zero trigger and 1mV per div (or most sensitive) and get the scope to free-run, switch probe to 10x and you should be able to scope the xtal oscillation.

Depending on scope/probe/oscillator, sometimes this can stop the xtal , don't panic, no damage will be done, would just need to find another test for scope.

4

Its working now.

I feel silly now too: forgot the GND and trigger voltage (allthough I dont understand why the threshold level seems only adjustable for analog channel A+B)... :cold_sweat:

Foggiest:
Zero trigger and 1mV per div (or most sensitive) and get the scope to free-run, switch probe to 10x and you should be able to scope the xtal oscillation.

Interresting! Since Im new to scopes I dont get "Zero Trigger", "Free-Run" and where do I have to connect the probe to measure the xtal of which device (arduino or the internal dso xtal)?

Thanks guys for your help!

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5

Scopes are complex buggers, so don't feel intimidated, everyone takes a while learning them.

A scope will sit there doing nothing, until a voltage on the input crosses the trigger threshold, then the trace is sent across the screen at a speed set by the timebase.

This is a reason why an incorrectly set trigger can make a scope seem broken and inactive.

Here's a couple of vids, watch these and let us know how you get on.
Always ask if unsure, better than blowing up your equipment.

I was talking about the xtal on the arduino, an old trick to check that the clock is running.