Hi guys, I have my NodeMCU v3 connected a serial port (module, Raspberry pi,...) where I can read the text sent by Arduino. Here is the code: unsigned long lastCharTime = 0; #define BAUD 38400 void setup() { Serial.begin(BAUD); // for debug only Serial1.begin(BAUD); } void loop(){ if(millis() - lastCharTime > 10000){ Serial1.println("hello world"); Serial1.flush(); lastCharTime = millis(); Serial.println("Sent.."); } //delay(1); } But I got some weird characters: kello world kello0world hunlo,worleM� oumoo�wo{ow�� The Baud is same on both sides and using different baud do not solve the problem. But I notice when I add delay (best 1ms) on loop function I receive only 10% of the time undesired characters on message, and 100% without delay. Using Serial1.flush() or not do not change nothing. Why delay affect the serial writing if things in Arduino happen synchronously? How to avoid those weird characters? Thanks

add GND - it's needed for both device to agree upon what 0 and 1 are (and protect your Rx pins from possible seing an over voltage)

bits flip --> you have noise on the line. Use shorter cables/shielded cables/reduce baud rate ...

I was thinking about the female jumpers I'm using may be the problem. So now I just solder male jumpers directly on it but still same problem.

[image] Common ground and why you need one General Electronics A common mistake for people new to electronics is to have 2 circuits fed from different power supplies with signals passing between the circuits, but with the grounds not connected. This leads to questions asking why the project doesn't work. You don't have to spend long reading the questions on this forum to see this is asked often. Here I attempt to explain the problem and why it matters to connect the grounds. Note that in all of the schematics that follow I have used a battery as a power sup…

I remember reading the article provided by @PerryBebbington, which may make sens in my case but I tested then it just stop receiving message. The two devices have separated power source (ok not really, all are connected to different USB port but same PC).

[image] kamoba: The two devices have separated power source (ok not really, all are connected to different USB port but same PC). you need it. if it does not work your problem is elsewhere, but you do need Rx to Tx and GND to GND (with compatible voltage from Rx to Tx)

Yes I thing you are right, the problem was missing GND. Once I used a different power source I got the reverse, now I do not receive any message anymore without GND and when I plugged the GND I started receiving message without any weird characters. But common ground do not work if devices connected to same PC. I have to remember "common ground"! Thanks!

I am curious to see your receiver codes.

Relation between delay and baud rate for Serial

Projects Programming

PerryBebbington January 20, 2024, 8:32am 7

Topic		Replies	Views
How to get your Arduino to tell you its Serial baud rate Programming	33	907	January 11, 2026
Serial receiving weird characters Networking, Protocols, and Devices	2	219	May 14, 2024
Random Characters generated in Serial console Programming	6	912	March 30, 2023
Weird characters when giving arduino any string Uploading	12	1373	August 24, 2023
How accurate is DELAY function? Programming	13	527	June 17, 2025

Relation between delay and baud rate for Serial

Related topics