The tx led on my nano board is always on. This appears to be preventing a new sketch download. Another nano board I have does not have this problem.
Unfortunately I don't now know what sketch was downloaded to the board. I have tried holding down the reset button and disconnecting and reconnecting the USB connection. This does not work.
I don't want to discard this nano board unless absolutely necessary. There must be a way to fix this. My USB lead from computer works on the other nano board so this cannot be the problem.
Can anybody suggest a fix to this problem?
- Try and re-burn the boot-loader.
The TX led is driven by the serial-to-usb converter so I would suspect that chip. On official Nanos it's a FTDI232 chip, on clones it's usually a CH340.
Is the IC on the bottom of the board marked. If yes, what does it say? If no, it's more than likely a reject CH340 which can be problematic..
If you press and release the reset button, does your board give a single flash of the L-LED, a couple of flashes in quick succession (I think three) or no flashes at all. A single flash indicates old boot loader, a few flashed would indicate new boot loader and no flashes would indicate that the boot loader or the 328P is malfunctioning.
I have seen that with another Nano board when only the pwr led is on the sketch compiles ok. With the current Nano the pwr and tx leds are on and a new sketch cannot be uploaded. No errors shown other than cannot SYNC.
I have seen this on the internet in google search. 'when the tx pin is low the tx led turns off.' I am getting the opposite. When I connect tx pin to the 5v pin(high) the tx led turns off.
Can anyone explain this and how can I now use this nano board to upload sketches?
I have merged your cross-posts @petercl14.
Cross-posting is against the Arduino forum rules. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend a lot of time investigating and writing a detailed answer on one topic, without knowing that someone else already did the same in the other topic.
Repeated cross-posting can result in a suspension from the forum.
In the future, please only create one topic for each distinct subject matter. This is basic forum etiquette, as explained in the "How to get the best out of this forum" guide. It contains a lot of other useful information. Please read it.
Thanks in advance for your cooperation.
It is a CH340 and therefore a clone. No flash of L-LED. Thus as you say bootloader or 328P malfunctioning. Not sure how to reburn the bootloader if that is the problem. If the 328P then I would discard this nano board.
I have 2 other nano boards and no similar problem with them.
That sounds like a serial flood to me, I have seen it many times. That happens when the Arduino is sending data faster then the IDE can process it. Put a delay(3000) in your setup before initalizing the serial. That normally will let the boot loader to get control for the IDE.
Serial Flood
Steps to Recover Your Arduino Board from Serial Flood:
Power Off the Board: Completely turn off your Arduino board by removing the power source.
Disconnect the USB Cable: Unplug the USB cable from the board.
Hold the Reset Button: Press and hold down the Reset button on the board.
Alternatively, you can run a jumper wire from the RESET pin to the GND pin.
Reconnect the USB Cable: While still holding the Reset button, reconnect the USB cable to the board.
Start Uploading a New Sketch: Begin uploading a sketch that does not produce the same problem (e.g., the Blink sketch).
Release the Reset Button: When you see the Receive light blink, release the Reset button.
Modify Your Code: To prevent the issue from recurring, add a delay(3000); or a longer delay in the setup() function of your sketch. This delay allows you to recover easily from a serial flood.
Note: This problem often occurs when the serial output is flooded, indicated by the TX light being stuck on.
receive light does not blink. upload of new sketch does not complete as before.
If you don't have a programmer you can use one of your other Arduinos as a programmer. You can find instructions on the web; see e.g. post #2.
If burning the boot loader fails you can discard the board or try to use it as a serial-to-usb converter. If it seems to work but you still can't upload using the normal way you can start further troubleshooting.