Hi, some code I was using on my Uno that was working perfectly (outputting on serial monitor correctly) does not seem to work on my Mega. It is receiving serial input (the Rx light flashes as it should), but I simply can't serial.read (I think) correctly. To be clear, the problem is no serial monitor output, beyond the Serialprintln("This works") in setup. I would just keep using the Uno, but I need the Mega's multi serial ports for this project. Any ideas on what's happening? Only thing I've seen mentioned was to put pinMode( 15, INPUT_PULLUP) in setup - I tried it and this did nothing. Thanks for the help! const unsigned int MAX_MESSAGE_LENGTH = 8; char message[MAX_MESSAGE_LENGTH]; unsigned int message_pos =0; void setup() { Serial.begin(115200); Serial.println("This works"); } void loop() { //Check to see if anything is available in the serial receive buffer while(Serial.available() > 0) { //Read the next available byte in the serial receive buffer char inByte = Serial.read(); //Message coming in (check not terminating character) and guard for over message size if ( inByte != 'n' && (message_pos < MAX_MESSAGE_LENGTH -1) ) { //Add the incoming byte message[message_pos] = inByte; message_pos++; } //Full message received... else { //Add null character to string message[message_pos] = '\0'; long number = atol(message); Serial.println(number); //Reset for the next message message_pos = 0; } } }

If you are connecting to pins 14 and 15, that is Serial3. Post a schematic showing how the wiring should be. Post photos showing how the wiring is.

Thanks for the response! I'm not connecting to any pins actually, this is purely just USB in - which is why I'm so confused as to why it's struggling..

I suggest you start by getting the code to compile.

Code compiles, I copy pasted with an extra bracket in my original post but its been edited (I deleted something incompletely). Again, like I said originally, this already works with my Uno.

So you are typing into the send box in the serial monitor? The code that you posted will not compile. error: 'message_pos' was not declared in this scope error: 'MAX_MESSAGE_LENGTH' was not declared in this scope error: 'message' was not declared in this scope

Apologies, the edit to the post is showing up for me now, the declarations in the beginning were missing. Just tried it now and it works, thanks again.

No, this is receiving serial data from a raspberry pi python script, the port, baud, etc.. I've double checked and are all correct (nothing's changed since the Uno).

I believe it works now, let me know if there's still an issue.

[image] numlock13: No, this is receiving serial data from a raspberry pi python script, the port, baud, etc.. That kind of information should have been provided in the first post. Please read the forum guidelines to see how to make a good post.

[image] numlock13: inByte != 'n' Terminating on a lower case N?

[Serial issue] Exact same code wont work on Mega, but works with Uno

Projects General Guidance

groundFungus August 17, 2022, 6:52am 17

Robin2's serial input basics tutorial may be of interest.

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[Serial issue] Exact same code wont work on Mega, but works with Uno

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