Floating serial issue [SOLVED]

Hello, i have a master board sending commands to a slave board via serial 2. When master is loaded with new code, slave receives plenty of nonsense. Any elegant way, avoiding pulldowns, to avoid this nuisance? Thanks

Solution
on the slave board, setup section, add after (or before)
Serial2.begin(115200);// ~100us/char
the line
pinMode(RX2_PIN, INPUT_PULLUP);
with RX2_PIN correctly mapped

Any elegant way, avoiding pulldowns, to avoid this nuisance?

Post your code, post your schematic.

It is a nuisance, isn’t it?

You really haven't provided any useful information or schematic.
If you want help you have to start at the beginning and explain EVERYTHING and include a schematic
if possible.

@HAL9000,
What happened ? Did you max out the post counter ?

Hi,
Have you got the gnds of the two controllers connected?
What model Arduinos are you using?

Thanks… Tom… :slight_smile:

TomGeorge:
Hi,
Have you got the gnds of the two controllers connected?
What model Arduinos are you using?

Thanks.. Tom.. :slight_smile:

Thank YOU Tom,
Both are mega board sitting by solderless cards, both (mega and solderless) mounted on a plastic support platform from sparkfun
Yes the two board's grounds are connected.

Again, issue is while master is undergoing code download. In this situation, there is noise AND outputs (master Tx) are (i think) threestated.

Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks… Tom… :slight_smile:

guy_c:
Hello, i have a master board sending commands to a slave board via serial 2. When master is loaded with new code, slave receives plenty of nonsense. Any elegant way, avoiding pulldowns, to avoid this nuisance? Thanks

You may try using a GPIO from the master connected to the slave as a ValidMasterSignal and monitor that signal, at the slave end, for MasterIsValid and from there do the blah and blah and blah thing.

TomGeorge:
Hi,

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom.. :slight_smile:

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Image of OP's rat's nest, posted properly. Note the area circled in RED!

Is the white wire making a good, secure connection?

Idahowalker:
You may try using a GPIO from the master connected to the slave as a ValidMasterSignal and monitor that signal, at the slave end, for MasterIsValid and from there do the blah and blah and blah thing.

Any elegant way...

@guy_c, have you considered how much current is drawn through your bread board vs how much current a breadboard connection can supply?

guy_c:
Thank YOU Tom,
Both are mega board sitting by solderless cards, both (mega and solderless) mounted on a plastic support platform from sparkfun
Yes the two board's grounds are connected.

Again, issue is while master is undergoing code download. In this situation, there is noise AND outputs (master Tx) are (i think) threestated.

So if you are not downloading code, you have no noise?
That is, when everything is loaded, and running, you have no noise?
While downloading code, turn the other controller OFF.

Trying to run any controller while downloading code to it will usually end in problems?

Sorry for the umteenth time, can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
This is a very important part of troubleshooting.

Tom.... :slight_smile:

Tx & Rx cannot be used for interfacing while code is being downloaded because those pins are used for code download. You need to remove the connections to Tx and Rx before downloading code and then you can reconnect them after the code is downloaded.

Post your code so we can see what lines you are using .

raschemmel:
Tx & Rx cannot be used for interfacing while code is being downloaded because those pins are used for code download. You need to remove the connections to Tx and Rx before downloading code and then you can reconnect them after the code is downloaded.

Post your code so we can see what lines you are using .

Tx2 is being used during download? Can you please post a link to this data?

Sorry, didn't notice you were using Serial-2.
No, it shouldn't be active during download.

TomGeorge:
roubleshooting

Trying to run any controller while downloading code to it will usually end in problems?.

Tom.... :slight_smile:

Never tried that ..

Hi,
Please reread post #13 and answer the question please?

So if you are not downloading code, you have no noise?
That is, when everything is loaded, and running, you have no noise?

Tom.. :slight_smile:

TomGeorge:
So if you are not downloading code, you have no noise?

Tom.... :slight_smile:

If i am not downloading code i have no problem.

TomGeorge:
That is, when everything is loaded, and running, you have no noisse

Tom.... :slight_smile:

Well, i always have noise as i suffer from tinnitus yet, when loaded, the system runs ok

TomGeorge:
While downloading code, turn the other controller OFF.

Tom.... :slight_smile:

This is not elegant

guy_c:
If i am not downloading code i have no problem.

This is not elegant

Why not, its practical and you are not going to be using the inter controller link while downloading.
The controller you are downloading to has its code suspended while the code is transferred, is this elegant?

How often will you be downloading code?

We still do not have a basic connection diagram.
A picture of your project does nothing except show that there are wires all over the place.
Which can be typical as you build the prototype, but at some stage you will need to dress those wires so you can see where everything is.

Why do you need the other controller?
If it is for more I/O, why not use a port expander?

Tom.... :slight_smile: