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# 0x48
- URL: https://sreekars-journal.labvion.com/pq-06-0x48/
- Published: 2025-06-22T12:30:00.000Z
- Updated: 2026-10-29T08:51:43.000Z
- Description: Seeing 0x48 after a blank serial monitor felt much bigger than the address looked. The controller had asked a question and something on the board had answered. That excitement is part of the project account, and the later log gives the communication result a precise record: one device at 0x48 o
- Author: Sreekar
- Tags: Power meter, #Import 2026-10-29 10:08

Seeing 0x48 after a blank serial monitor felt much bigger than the address looked. The controller had asked a question and something on the board had answered. That excitement is part of the project account, and the later log gives the communication result a precise record: one device at 0x48 on 22 June 2025\. The address has a reason too. The scanner and wiring notes associate it with ADDR connected to ground, so I can explain the small success rather than only remember the digits.

There’s something slightly funny about being this pleased with an address on a serial monitor. It isn't a graph, a voltage reading or a finished instrument. But the controller has asked a question and something on the board has answered. After spending time trying to understand the connection, that small answer feels much larger than it looks. It’s the kind of result I want to keep distinct from all the things the meter still has to do.

I like that the result is specific. The address is not simply a message saying everything works. It tells me where a device responded on I²C. That makes it useful when I return to the connection later. If I only remember that the scanner worked once, I lose the piece of information it actually gave me. Keeping 0x48 beside the setup gives the next check something to compare with. It also makes it easier to explain the milestone without turning it into a bigger claim than it deserves.

The notation itself is worth slowing down for. The 0x tells me the number is written in hexadecimal. In decimal, 0x48 is 4 times 16 plus 8, which is 72\. Changing the notation hasn't changed the address or discovered another device. I can imagine confusing myself if one source prints 72 and another prints 0x48 and I treat them as different results. This is a small example of a problem that keeps appearing in electronics: a value needs its meaning and representation alongside it, not just its digits.

The response doesn't mean the ADC is sending the right measurements yet. I have not established the selected input range, the channel behaviour or the conversion from raw codes. Those are still separate questions. I'm trying not to spoil this success by expecting it to answer all of them. There’s a real difference between saying that communication has started and saying that the meter is accurate. The first can be an important success without pretending to be the second. That makes the progress easier to understand rather than less exciting.

The saved scanner makes the boundary easy to see. It starts a transaction at each address and looks at the result when the transmission ends. It does not request an analog channel or apply the sensor's calibration. That means the success can stay small without becoming unimportant. There’s a real result to compare against when examining communication, and there are different programs for the next stage. I don’t need the address to establish accuracy in order to enjoy what it does establish: a device answered where the setup expected it.

I can see the next steps more clearly now. A channel reading will give me a number that changes with the input signal. Then I have to know the scale of that number. If the signal has been shifted around a midpoint, I have to account for that shift. If the sensor represents a larger quantity with a smaller signal, I have to understand the relationship. The scanner has not performed those steps, but it has given me a place from which to begin them. Before this, even the communication was another uncertainty in the same pile.

A thought experiment shows why I want to preserve the scanner. In this case, the full program later prints an unexpected current value. I could immediately change a calibration multiplier, but that assumes the raw reading is arriving correctly. Going back to the smaller communication question helps me avoid skipping a stage. If a device no longer responds, the power formula is a very strange place to start looking. If it does respond, that still doesn't settle the measurement, but it lets me move to the next part with a clearer question.

Even a small result gives me more than one thing to think about. I have the address, the idea of a response and the route the program used to obtain it. I want to be able to explain those without turning a useful library into a box that I’m afraid to touch. That doesn't mean rewriting the library. It means understanding the particular job I have asked it to do and recognising the point where its answer stops.

What I enjoy about this stage is that the program has stopped being only text I read on a screen. Its result depends on a physical connection. The code and the board are doing something together, even though the thing is small. It gives me a different reason to understand the library calls. They aren't just the lines before the interesting measurement. They are part of what makes it possible to get information from the hardware in the first place.

I'm keeping the scanner as a separate sketch instead of burying it inside the next version. It has one clear job, and I suspect that will make it useful again. Next comes the harder question of what the channel reading means. There will be more chances to get confused by ranges, offsets and calculations. For this moment, though, I can look at 0x48 and explain why it matters. It’s a small, definite answer in a project that still contains plenty of open questions. I'm quite happy with that.

The next number will need a scale and a channel. This one needs an explanation of communication, and I can give it one. For such a short line on a serial monitor, that is quite a satisfying amount of progress.