Loop Back Test - Sticky?

Last chance. Any suggestions...

  1. Disconnect power from the board

  2. Remove all connections and shields from the board

  3. Force the processor to remain in reset by connecting a jumper from RESET to GND

  4. Connect a jumper from the TX pin (Digital Pin 1) to the RX pin (Digital Pin 0)

  5. Connect the board to your computer. After a brief pause Windows will produce a device-insertion tone if sound is enabled. Linux may or may not produce a device-insertion tone; an entry is added to the system log.

  6. Start your favourite terminal application. Serial Monitor will work fine.

  7. Connect the terminal application to the serial port for your board. The baud rate is irrelevant.

  8. Send data by typing. Everything you type should be echoed back. To send data, some terminal applications, like Serial Monitor, require pressing the Enter key or clicking a Send button. If exactly what you send is echoed back then the board passes the test. This means that the host computer hardware driver, USB cable, and USB to serial converter are all working.

  9. Shutdown the terminal application

  10. Disconnect the board from the computer

  11. Remove the two jumpers

Why the word Uno in step 4? Applies to all arduino boards, might confuse.

  1. Connect a jumper from the TX pin (1 on the Uno) to the RX pin (0 on the Uno)

How about:

  1. Connect a jumper from the TX pin (Pin 1) to the RX pin (Pin 0)

Or:
4. Connect a jumper from the TX pin (Shield pin 1) to the RX pin (Shield pin 0)
Or:
4. Connect a jumper from the TX pin (Arduino Pin 1) to the RX pin (Arduino Pin 0)

Lefty

Why the word Uno in step 4?

Huh. Good question. Digging through my brain reveals... not much. :smiley:

I guess because I didn't know if pins 0 & 1 are RX & TX on other boards. Is that consistent with Arduinos? Is that consistent with compatible boards?

Yes, if you are talking about the AVR hardware UART channel, even on the mega it uses (shield) pins 0 and 1 for the Serial channel, where the other three hardware UART channels are in the pins 14 to 19.

You software guys crack me up, often. :wink:

Lefty

You software guys crack me up, often.

:smiley: We do what we can to entertain.

What do you think of this...

  1. Connect a jumper from the TX pin (Digital Pin 1) to the RX pin (Digital Pin 0)

I like it.

Thanks!

Anyone else? Anything else?

Connect a jumper from the TX pin (Digital Pin 1) to the RX pin (Digital Pin 0)

Strictly speaking, they aren't pins. If you are going to worry about people not hearing sounds because the volume is down, you might point out that they are sockets. It's the male/female thing. The boards only have a handful of pins, the rest are sockets.


And I can't resist this:

Graynomad:
I hope I'm not splitting hairs but this is for beginners.

Windows produces a device insertion tone

Not if sound is disabled.

Warning: if you are deaf you won't hear it.

You certainly have a valid point. Unfortunately, the Arduino folks call them "pins" A. I prefer to use the same term used in the rest of the Arduino documentation to avoid confusion B.

A Which has been a source of confusion even for advanced users (Did you mean "physical pin" or "Arduino pin"?).

B Oh, the irony!


Warning: if you are deaf you won't hear it.

XD

As part of a previous job, I occasionally had to install a complete computer system (PC + custom software). I arrived at one of the sites and found the two operators. One of the operators ("Buddy") was bragging to the other ("Juan") about the new tires on his truck. He claimed to have reached more than 80 miles per hour and successfully navigated an especially sharp corner. I had a suspicion Buddy would need a bit more training than usual.

I carried in the various computer parts and connected them. When I left the office to get the software and some notes, the computer was fully assembled so I started it booting. I returned to the office to find Buddy waving the mouse in front of the monitor with a very confused look on his face. Juan watched for a moment and then told him, "Buddy, you have to drag it across the table." I very nearly burst out laughing; I had to actually cover my mouth. I turned around, walked out the door, sat down in my vehicle, and laughed my gut sore.

Despite his naiveté, Buddy was up to the task. He quickly learned, not only to use a mouse, but to use the software.

The moral of the story? While instructions like "Warning: mouse only functions correctly when used on a flat horizontal surface" are sometimes necessary, "Warning: if you are deaf you won't hear it" is probably over the top.

Now a sticky...
http://arduino.cc/forum/index.php/topic,73748.0.html

Please continue posting suggestions here.

Is it safe to assume that newcomers will know that they should look for how to perform a 'loop back test' when uploading doesn't work?

The title of the sticky post doesn't say anything about failing uploads.

Actually, after the revisions suggested above, this is really good. The only thing that struck me was that when I first saw it I asked myself, "What do I want to do a loopback test for?" Perhaps, something about why one would/should do a loopback test?

I tried the procedure and had no difficulty following it.

The slight change I wanted to suggest was that some of the text in step 8 should be removed and instead there should be a short introduction saying why you would do the test and what it would achieve. I reached this conclusion before reading this thread where one of the comments is;

The only thing that struck me was that when I first saw it I asked myself, "What do I want to do a loopback test for?"

Suggested text at the start (removing equivalent text in point 8 );

The loopback test will prove that your host computer hardware driver, USB cable, and USB to serial converter are all working.
Try the loopback test after you first install the system or if you cannot upload sketches.

madworm:
Is it safe to assume that newcomers will know that they should look for how to perform a 'loop back test' when uploading doesn't work?

No.

The title of the sticky post doesn't say anything about failing uploads.

What should the title be?

What introduction (cover) should be added? Perform a loop-back test when...

draythomp:
Actually, after the revisions suggested above, this is really good.

Excellent!

The only thing that struck me was that when I first saw it I asked myself, "What do I want to do a loopback test for?" Perhaps, something about why one would/should do a loopback test?

I agree. One case is: uploading was working, upload is not now working, damaged processor is suspected. When else would / should a loop-back test be performed?

radman:
I tried the procedure and had no difficulty following it.

Excellent! Thank you.

The slight change I wanted to suggest was that some of the text in step 8 should be removed

Nope. Not going to happen. My Tech-Com II professor stated repeatedly: You tell it to them three times. You tell them what you are going to tell them in the introduction. Then you tell them in the body. Then you tell them what you told them in the conclusion. After working in technical support for a few years, I strongly agree. Some people get it the first time they read something. Some people barely get it the third time they read something. Troubleshooting instructions need to be written for the latter group; lots of repetition.

and instead there should be a short introduction saying why you would do the test and what it would achieve

I agree. It needs an introduction / cover.

Suggested text at the start (removing equivalent text in point 8 );

The loopback test will prove that your host computer hardware driver, USB cable, and USB to serial converter are all working.
Try the loopback test after you first install the system or if you cannot upload sketches.

Is it necessary to perform a loop-back test after first installing the system?

Is it necessary to perform a loop-back test after first installing the system?

No. The loop-back procedure is a troubleshooting aid/procedure to help one determine if serial communication between the PC and Arduino board is working or not working in a typical arduino installation. It does no harm to run it on a working system, and it would probably be best to learn to run it on a working system before having a problem to prevent false positive (or is it false negative?) testing results.

Lefty

Is there really just one use-case? "uploading was working, upload is not now working, damaged processor is suspected"?

How's this for the introduction...

The loop-back test is a troubleshooting procedure to determine if serial communication between the PC and Arduino board is working in a typical Arduino installation. The test proves that the host computer, hardware driver, USB cable, and USB to serial converter are all working.

How's this for the introduction...

Needs a comma between "host computer" and "hardware driver". It is testing all 4 items.