Thanks, Dave. I just want to add, too, that this technology is the same in all appliances, regardless of manufacturer, which use a computer board with one or more sub-boards. This is how these boards talk to each other using serial data communications. The only thing that varies among manufacturers is how they label these lines. But there will always be data lines, DC supply, and DC ground. You can usually identify DC ground and DC supply easily enough. But different manufacturers will use different callouts for the data lines. In this case, Samsung used intuitive labelling and made it easy to know which was transmit and which was receive. It's not always that easy to identify which is which. 

Correctillia. Just use your DMM at the same test points you would use an o-scope. Your DMM will report an average DC voltage reading back to you, somewhere between 0 and 5 VDC. The closer those pulses are together (higher frequency), the higher the average voltage reading on your meter. As a general rule, any reading above 1 VDC is a pretty good indication that there's serial data communications going on. 

23 minutes ago, micabay said:

This right here is why a good meter (such as a fluke 116) is needed.  I had to do without my fluke for a few months. My backup meter (Klien MM2000) takes longer to read voltage.  It would just jump around showing no values until the voltage was steady for a half second or more. 

Excellent point and so true! I had this exact same problem with my old Radio Shack DMM-- jumping around and not showing me what was really going on in the circuit. I should have made that point in the video. A DMM will do the job but it has to be a quality DMM. Radio Shack, Klein, whatever, just don't make the grade. 

If you're not going to carry a scope to check data lines, spend the money and get a Fluke. 

The data on the RX and TX lines are just pulses of DC voltage. So whether you're using an oscilloscope or a digital multimeter, you're still going to connect to the circuit the same way. 

Electrically, an oscilloscope connects to the circuit the same way as your DMM. The only difference is that the 0-scope lets you see a graphical representation of these pulses instead of showing digital readout of the mathematical average DC voltage. But they are both electrical meters so both connect to the circuit at the same two points: the point of interest (RX or TX, in this case) and the reference for the point of interest (DC ground). 

Make sense?

5 minutes ago, BoardFruit said:

What's even cooler about this device is that it is also a pattern generator.  Once you capture a "good" communication protocol you can mimic it with this device to drive OEM peripherals as if you are the OEM motherboard.  

That's a cool feature. Problem is capturing that protocol because they move around so much. Often takes more time than we usually have on a service call in a customer's home. 

The oscilloscope I used in the video is made by Oscium, model iMSO-204L. It costs about $400 and connects to my iPad (which I always have with me on service calls anyway) so it's very little overhead in terms of extra equipment to haul into the house on a service call-- fits nicely into my tool bag. 

My use for o-scopes in service calls is mostly to check for the existence of a "pulse" on data lines that should be active. The DMM gives a rough approximation of this by reporting an average DC of the pulses and/or a frequency. But it's cool to see the actual pulses. It's like watching red blood cells in action!