Can you provide the history of the board. Is it new and never worked or did you use it in the past with success? If the latter, what was the last project that you worked on when it was still possible to upload; we might be specifically interested in the fact if there were (or now are) voltages involved different from the 5V and if anything related to motors, relays etc. were / are.
Your PC seems to be a Mac; I don't have experience with it.
The first question would be if that device disappears from the IDE when you disconnect the board. As it says Uno at the end and the VID/PID match the VID/PID of a genuine Uno I suspect that it will.
You can try the loopback test. I suspect that it will fail.
The second question is what your Mac thinks of your board. As I do not have experience with a Mac I can't tell you where to start digging but you might know; it would be somewhere in the system logs (under Linux it would be the dmesg command).
You did a bit of research by the looks of it Lots of useful details. The only thing that you have missed is the avrdude command that is issued by the IDE. If you enable verbose output dutring upload under file/preferences in the IDE and perform an upload the first few lines after the memory report will contain that information.
yes. The board is old. Last time i used it was something like 2013. Since then it sat on the shelf. It had been used (back in 2013) to drive a stepper motor to control focus on a video camera. ( i was working on this short: https://vimeo.com/manage/videos/100793579) I had two shields mounted on her: a ProtoShield housing an Easydriver v4.4 (Easy Driver stepper motor driver) and a Unified Microsystems ATS-1 terminal shield. When these are connected today, the code that i wrote (and is apparently still uploaded) starts running (and it seems to run fine, although i coded it fairly clumsily, so i can't report it with absolute certainty).
It's been over 10 years, so it's somewhat difficult to remember everything, but I believe that it was 5v -- and it wasn't powerful enough, so I switched to bigger motors, higher voltage, and a different controller (an app written in Object-C on mac). But that's a different story--nothing to do with this board.
So to sum up: motors -- yes, voltages different from 5V -- no.
Can you remember if there is any serial communication implemented in the sketch that is still loaded? If yes, do you still see output (if applicable) in e.g. serial monitor or can you control the sketch from serial monitor (if applicable)?
The three quick flashes after releasing the reset button indicate that the boot loader is still function. Combined with the fact that the sketch still seems to be running the 328P processor should be OK.
#define BELL 0x07 //Character to send to the ATS-1 to generate a beep
#define CLS 0x01 //Character to send to the ATS-1 to clear the LCD and home the cursor
#define LED_ON 0x11 //Character to send to the ATS-1 to turn LED on
#define LED_OFF 0x12 //Character to send to the ATS-1 to turn LED off
#define GOTOXY 0x14 //Move cursor to XY position
#define CUR_LEFT 0x16 //Move cursor left 1 char (arrow key)
#define CUR_CR 0x0D //Carriage Return – moves cursor to first
#define CUR_LF 0x0A //Line Feed – moves cursor to other line, same horizontal position
i found a version of the old code. it's most likely not the code presently uploaded onto the UNO, but an another version. still now i have some idea. And i'm starting to think that maybe it is not running fine. I can't tell for sure because i don't know what is loaded -- it might be the case that i loaded some incomplete sketch onto the UNO, and left it. So it's one of the two: either an incomplete sketch is loaded, or the unit is not operating properly.
i opened the Serial Monitor on Arduino IDE. On the reset, it shows:
Lots of useful details. The only thing that you have missed is the avrdude command that is issued by the IDE. If you enable verbose output dutring upload under file/preferences in the IDE and perform an upload the first few lines after the memory report will contain that information.