Nano 33 BLE serial port

I am using the Nano33BLE to drive voice synthesiser via the onboard serial port. The port does not seem to work. The same code works OK on an UNO so I'm a little confused. Reading various postings on this subject suggests that I'm not alone. Can anybody shed any light on my problem? Please.

Hi @nikharrison. We’ll need more information in order to be able to help you.

Please post your full sketch.

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We also need to know exactly how the voice synthesizer is connected to the Nano 33 BLE.

  Modified 17/04/20


  This was done to test the Voice Synth only.



unsigned long start;
unsigned long timeout = 60000;
int done;

void setup() {

  Serial.begin(9600);         // Using Ch0 and Ch1

  char buf[64];

  speak("[x0][t6][v7][s6][m52][g2][h2][n1] Hello Harry.");  // set up tone/character etc of voice

  //  =====================
  //  Prototypes here

  void VoiceOut();
  void speak(char* msg);
  void waitForSpeech();


//  =====================
//  Main loop here

void loop() {



//  =====================
//  Functions here

void speak(char* msg) {
  Serial.write(2 + strlen(msg));

//  ==================

void waitForSpeech() {
  start = millis();
  done = false;
  while ( ! done && (millis() - start) < timeout ) {
    while ( Serial.available() ) {
      if ( == 0x4F ) {
        done = true;

//  ==================

void VoiceOut() {

  speak("Hello World");

//  ==================

This is the reduced code that works OK on my UNO but not the Nano33BLE. I’m using an Apple laptop.
I have loaded a .pdf of the connections I’m using. Hope this all helps. Cheers.

Sound Controller.pdf (31.7 KB)

Unlike on the Uno, the pins on your Nano 33 BLE marked "RX0" and "TX1" are the Serial1 interface, not Serial. So you just need to change all the occurrences of Serial in your code to Serial1.

This is a nice improvement on the Nano 33 boards. On the Uno, pins 0 and 1 are also used for communication with your computer. This means that if you connect something to those pins on the Uno, it can make it so you can no longer upload to the Uno without removing that connection. It also means that any debug output you try to print to Serial Monitor can interfere with the communication with the device connected to those pins. On the Nano 33 BLE, the two are separate interfaces, so you can use the RX and TX pins as you like without causing any interference with communication with the computer.

Thank you for the quick reply. I’m now sorted. It also explains why I had to disconnect the synth board before I could download to the Uno. Thanks again.

You're welcome. I'm glad to hear it's working now. Enjoy!