Hi, I'm a college student from Philippines. We have a group project and it is entitled "Arduino Based Digital Network Cable Tester" and the output looks like in 'screen.png'.
Its required functions is to draw the pin connections of the RJ45 cable into 128x64 Graphics LCD. Also, it can measure electrically the "length of the cable".
I've read about Timers/Counters of atmega2560 in ebooks and its datasheet. But I find it difficult. I don't know where to start. I don't know how. I'm just a beginner in Arduino programming.
If you could help me, it is really a big help.
Thanks very much.
God Bless.
IIRC (and I'm prepared to be corrected) a rule of thumb is that a signal travels at about 1 foot per 1nS. Your cable had better be very long to have any chance of measuring it with an Arduino.
Unless there's some trick your teacher knows about I can't see any way to measure a cable length with an Arduino.
IIRC (and I'm prepared to be corrected) a rule of thumb is that a signal travels at about 1 foot per 1nS
That's true for light in a vacuum, but quite a bit slower in copper, maybe 2c/3 for co-ax.
Still a bit quick for an Arduino without hardware assist.
(Google "Time-domain reflectometry")
"...Electricity travels through a wire at approximately two-thirds the speed of light (200000 km/s - 0.2 m/nanoseconds), which means that it travels at approximately two-thirds a foot per nanosecond... "
The Arduino oscillator runs at 16 Mhz. Do the math:
One cycle is 1/16,000,000 = .063 MicroSeconds. That's 63 Nanoseconds. That's about 30 feet of cable. So even IF you added you own counter hardware AND pulse detection circuitry that would see the far-end reflection and stop your counter, you'd have errors of at least 30 feet.
So you need to study "Time Domain Reflectometry" and find some external circuit that someone has designed that you could both duplicate AND control from Arduino.
For 1 foot accuracy, you'd need to run at least a 500 Mhz counter and have good detection circuitry for the reflected signal.
Read about using an oscilloscope for this; you will need that ability to check what you are getting for results.
