I noticed something odd: when two Unos (and later I tried with 2 Nanos and same effect) are bare-bones (not attached to anything else and have very simple basic code) are set up so one "talks" to the other via Serial with a ground wire between them with a speed of 115200 Baud the test message "TESTHOME1234" passes perfectly every time (the sender pauses 2000 mS each time). Both Unos / Nanos are Serial.begin( 115200). Everything works 100% of the time at this point. Now, Serial.begin( 9600 ) for both Nanos. The receiving nano gets parts of the incoming message. There is no other change in the hardware or software. Just setting Serial.begin( ) to 9600 rather than 115200. I wondered if one or both of the boards was "slow" so replaced both (sender and receiver) with fresh nano boards: no change in the situation. I expected the reverse to occur (things go bad at high speed) but it seems the 115200 is stable, the 9600 is not. I can not find any explanation on the internet. Any help here why this might occur is appreciated. PS: To be clear: The battery ( 6V lantern feeding both) and everything else (hardware) does not change. The code does not change EXCEPT for both speeds being set to 115200 or 9600. It appears it works perfectly at 115200 but not at all at 9600. '

Please post the sketches that you are using

#define nHow_Long_Tx_Delay_Interval 1500 // if Tx in infinte loop in setup(), how long delay in mS? #define nSTARTING_Serial_Speed 115200 // used in setup() Serial startup speed #define nSend_Or_Rec 2 // 1 IS SENDER 2 IS RECIEVER String sInCommingString = ""; char InChar = ' '; void setup() { pinMode( 10 , OUTPUT ) ; // POWER PROOF ON LED for ( byte i = 0 ; i < 5 ; i ++ ) { Flash_D13_FAST( 1 ) ; } digitalWrite( 10 , HIGH ) ; Serial.begin( nSTARTING_Serial_Speed ) ; delay(10); pinMode( 13, OUTPUT ) ; #if nSend_Or_Rec == 1 while (1) { Serial.println( ("TESTHOME1234" ) ) ; delay( 75 ) ; Serial.flush() ; delay( 75 ) ; delay( nHow_Long_Tx_Delay_Interval ) ; Flash_D13_FAST( 0 ) ; } #endif } void loop() { // next check for a correct incomming Serial message sInCommingString = ""; InChar = ' '; while ( (Serial.available() > 0) ) { InChar = Serial.read(); sInCommingString += InChar; delay(1); } if ( sInCommingString.substring( 0 , 12 ) == "TESTHOME1234" ) { Flash_D13_VERY_SLOW() ; } } void Flash_D13_FAST( byte nIs_Booting ) { for ( byte i = 0 ; i < 7 ; i ++ ) { if ( nIs_Booting == 1 ) { digitalWrite( 10 , HIGH ) ; } digitalWrite( 13 , HIGH ) ; delay(20) ; digitalWrite( 13 , LOW ) ; digitalWrite( 10 , LOW ) ; delay(20) ; } } // ****************************************************************************************************************************************************************** void Flash_D13_SLOW() { for ( byte i = 0 ; i < 3 ; i ++ ) { digitalWrite( 13 , HIGH ) ; delay(100) ; digitalWrite( 13 , LOW ) ; delay(50) ; } } // ************************************************************************************************************************************************************* void Flash_D13_VERY_SLOW() { for ( byte i = 0 ; i < 3 ; i ++ ) { digitalWrite( 13 , HIGH ) ; delay(100) ; digitalWrite( 13 , LOW ) ; delay(100) ; } }

[image] SamBrownADK: It appears it works perfectly at 115200 but not at all at 9600. Your delay driven code leads to this effect. When you change the loop delay from 1 to 2, both versions will 'work'.

Thank you for posting your sketch but do you really work on it laid out like that ? Here it is after Auto Formatting it in the IDE #define nHow_Long_Tx_Delay_Interval 1500 // if Tx in infinte loop in setup(), how long delay in mS? #define nSTARTING_Serial_Speed 115200 // used in setup() Serial startup speed #define nSend_Or_Rec 2 // 1 IS SENDER 2 IS RECIEVER String sInCommingString = ""; char InChar = ' '; void setup() { pinMode(10, OUTPUT); // POWER PROOF ON LED for (byte i = 0; i < 5; i++) { Flash_D13_FAST(1); } digitalWrite(10, HIGH); Serial.begin(nSTARTING_Serial_Speed); delay(10); pinMode(13, OUTPUT); #if nSend_Or_Rec == 1 while (1) { Serial.println(("TESTHOME1234")); delay(75); Serial.flush(); delay(75); delay(nHow_Long_Tx_Delay_Interval); Flash_D13_FAST(0); } #endif } void loop() { // next check for a correct incomming Serial message sInCommingString = ""; InChar = ' '; while ((Serial.available() > 0)) { InChar = Serial.read(); sInCommingString += InChar; delay(1); } if (sInCommingString.substring(0, 12) == "TESTHOME1234") { Flash_D13_VERY_SLOW(); } } void Flash_D13_FAST(byte nIs_Booting) { for (byte i = 0; i < 7; i++) { if (nIs_Booting == 1) { digitalWrite(10, HIGH); } digitalWrite(13, HIGH); delay(20); digitalWrite(13, LOW); digitalWrite(10, LOW); delay(20); } } // ****************************************************************************************************************************************************************** void Flash_D13_SLOW() { for (byte i = 0; i < 3; i++) { digitalWrite(13, HIGH); delay(100); digitalWrite(13, LOW); delay(50); } } // ************************************************************************************************************************************************************* void Flash_D13_VERY_SLOW() { for (byte i = 0; i < 3; i++) { digitalWrite(13, HIGH); delay(100); digitalWrite(13, LOW); delay(100); } } It is so much easier to read without all of those empty lines

[image] SamBrownADK: InChar = Serial.read(); sInCommingString += InChar; delay(1); <----- You mean here? I annotated above

My remaining question now is why? Why is this an issue for 9600 but not 115200 (where I would expected it to be)? Thank you again in advance.

Your problem is not chars coming in too fast, but too slow, Your while terminates when you read one or more chars, waited a ms and found no more pending. Faster -> more pending. You should use a different method for serial input and for your timings. Forget delay, it is only useful for very primitive code.

I try to avoid delay(): I time compare instead. I used delay() here to make a fast and dirty demo. Thank you for the explanation: It is clearer now. i will follow up with more Serial class reading.

I will def brush up on my Serial now (I don't usually use it much). I used Strings (as opposed to say char array) just to be fast and simple for the demo. Thank you again for the link!

Works fine at 115200 but does not at 9600 baud

Official Hardware Nano Family Classic Nano

anon94801460 May 30, 2023, 9:35pm 9

I recommend the Serial Input Basics tutorial, and to avoid Strings.

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Works fine at 115200 but does not at 9600 baud

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