Control onboard LED turning serial transfer

Community General Discussion
1

I'm sending data over serial which should cause functions to fire on the unit. This is not happening. I want to use the onboard LED to blink when digitalWrite is called since I cannot print to the serial monitor (I get an error when I try). The blinking will tell me if my function is being called. So this is not an excercise in getting the light itself just to blink.

When I send data over serial to the mega the onboard lights go haywire, even thought I have no calls turning them on anywhere. I even explicity turn them off. This activity ruins my ability to use the lights as I want.

I've googled but all I get is the Blink tutorial. How can I do this? Where can I find out more about this particular blinkig during transfer activity?

This is a compact gist so there might be syntax errors. This is not runnable. I just want to know how to use the lights as I asked, which would not be related to any particular code anyway.

code removed

2

Maybe try fixing that?

3

Welcome to the forum

Please post a complete sketch that illustrates the problems that you have and use code tags when you do to make it easy to copy for examination

4

How? I have serial port open and data is going over it. That seems like the same port that the monitor uses.
I have tried this long before posting here.

5

I just want to know how to turn the light off during transfer. Should be enough detail there no?

And I did use code tags. At least they are showing up on my end.

6

That would suggest you are doing something wrong. Using serial print is a standard way of debugging.
How are you trying to debug? Note it needs to be a different serial channel than the one you are trying to use for your serial transfer.

What Arduino are you using?

You did but you did not post all your code.

What do you want to trigger this, if it is just a line of code then use digital write to turn it on when you send stuff, and turn it off some time later, maybe even use delay before turning it off just to test when your code is getting to that point.

7

Ok, I'll look at this again and see if I can get it to work. But the data is all coming in via USB which for me is COM8. Seems like the monitor uses this too maybe, and so cannot be used while data is going over it. I wasn't able to find another question about this issue but I did try.

My code is too dense to post as is. I'll post a more thourough example though.

8

Try and post some simple code that just illustrates what you want to do and can't.

9

You really should provide some more information:

what microcontroller are you using?
A lot of microcontrollers (but not all) have mimimum two hardware-UARTs or are fast enough to send data over two serial connections.

One for your application one for the serial debugging.
This requires a second USB-to-TTL-converter but you can buy them for 5 to 10$
Another option is to use such a logic analyser
https://www.ebay.de/itm/314021190415
You can even do decoding a lot of protocols including serial 8N1 etc.

best regards Stefan

10

I mentioned I'm using a mega in my post. It has 4 serial ports. The serial monitor is blocked by the incoming serial data and I can't use it concurrently. If I want help with this, I'll ask a separate question. Thanks for the other debugging info.

My question here is about the lights. How do I do what I asked with the lights?

11

The onboard 'TX' and 'RX'?
They're hard-wired - part of the plan, man.
There's no option to 'disable in firmware'.

12

Which function?

For serial transfer, it cold or should be as simple as

if(Serial.available())
{
  digitalWrite(LED_BUILTIN, LOW);
}
else
{
  digitalWrite(LED_BUILTIN, HIGH);
}

As long as data is in the serial buffer, the LED will be off, once you have read evevrything it will be on.

What is at the receiving end? How much control do you have over it? If it's some software that you wrote, you can add debug functionality to it.

Do you have a TTL-to-USB breakout board? You can hook that up to the Mega (e.g. Serial1) If not, do you have an Uno or Nano? If so, you can use them as a TTL-to-USB converter and use e.g. the Mega's Serial1 as your debug port; keep Uno/Nano in reset (with a wire), Mega TX1 to Uno/Nano TX, Mega RX1 to Uno/Nano RX and on the Mega, use e.g. Serial1.print.

13

@anon99272098
I could go reading again and again all postings trying to conclude what "the lights" exactly mean

But I won't do that.

Either you are able to describe very precise which "lights" you mean

  • the onboard yellow / green Rx / Tx Leds?
  • the single onboard red LED hardwired to IO-pin 13?
  • some other LEDs

I'm pretty sure that you did not write this code yourself because it uses things like

    msg_esc_setaux_t *msg = (msg_esc_setaux_t *)data;
    if (msg->id < ESC_COUNT)
    {
      // analog write
      set_esc_aux(msg->id);

because this is rarely seen advanced stuff.

best regards Stefan

14

Simpler yet:

digitalWrite(LED_BUILTIN, !Serial.available());
15

It seems it'll be impossible to get my question answered here. I'll find other means to debug.

16

With the greatest respect, I'd suggest that that's because nobody actually understands what your question is.

17

Use a lower value. The LED will blink.