Simple Hardware Serial

Troubleshooting and Support
1

Hello,

I am having trouble implementing a simple hardware Serial connection between the Daisy Seed and an Arduino Nano. I am programming the Seed with DaisyDuino.

I have confirmed that the Arduino is properly writing data by connecting another Nano as the receiver. This works fine.

However, when the Nano is transmitting to the Seed, the Seed never sees any data available.

Here is the simplified DS code I’m using to test:

#include "DaisyDuino.h"

DaisyHardware hw;

HardwareSerial hwSerial(15, 14);

void AudioCallback(float **in, float **out, size_t size) {
  for (size_t i = 0; i < size; i++) {
    out[0][i] = out[1][i] = 0.0;
  }
}

void setup() {

  Serial.begin(9600);

  hwSerial.begin(115200);

  hw = DAISY.init(DAISY_SEED, AUDIO_SR_48K);
  float sample_rate = DAISY.get_samplerate();

  DAISY.begin(AudioCallback);
}

void loop() {

  if (hwSerial.available() > 0) {
    int nfcData = hwSerial.read();
    Serial.println(nfcData);
  }
}

Here is the Arduino Nano Test code, which writes Serial data when a PN532 module detects an NFC card. This code is confirmed working when transmitting to another Nano.

#include <Adafruit_PN532.h>


#define PN532_IRQ (2)
#define PN532_RESET (3)  // Not connected by default on the NFC Shield

Adafruit_PN532 nfc(PN532_IRQ, PN532_RESET);

unsigned long lastNfcCheckTime = 0;

int nfcCheckInterval = 1500;


void setup() {

  Serial.begin(115200);

  while (!nfc.begin()) {
    delay(10);
  }

  pinMode(13, OUTPUT);
}

void loop() {

  if (millis() > lastNfcCheckTime + nfcCheckInterval) {
    lastNfcCheckTime = millis();
    checkNFC();
  }
}


void checkNFC() {

  uint8_t success;
  uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };  // Buffer to store the returned UID
  uint8_t uidLength;                        // Length of the UID (4 or 7 bytes depending on ISO14443A card type)

  success = nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, &uidLength, 100);

  if (success) {

    if (uidLength == 4) {

      uint8_t keya[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

      success = nfc.mifareclassic_AuthenticateBlock(uid, uidLength, 4, 0, keya);

      if (success) {

        uint8_t data[16];

        success = nfc.mifareclassic_ReadDataBlock(4, data);

        if (success) {

          Serial.write(data[0]);

          digitalWrite(13, LOW);
          delay(50);
          digitalWrite(13, HIGH);
        }
      }
    }
  }
}

Here is a picture of my wiring. On the DS I’m using pin 15 for Rx and 14 for Tx.

20250830_154721
20250830_1547211920×2560 593 KB

Hopefully I’m missing something obvious. Any help is much appreciated. Thanks in advance!

2

I’ve also tried a ‘loop back’ test on the Seed, to no avail. I plugged pin 15 (Rx) into pin 14 (Tx) and used the following code:

#include "DaisyDuino.h"

DaisyHardware hw;

HardwareSerial hwSerial(15, 14);

void AudioCallback(float **in, float **out, size_t size) {
  for (size_t i = 0; i < size; i++) {
    out[0][i] = out[1][i] = 0.0;
  }
}

void setup() {

  Serial.begin(9600);

  hwSerial.begin(115200);

  hw = DAISY.init(DAISY_SEED, AUDIO_SR_48K);
  float sample_rate = DAISY.get_samplerate();

  DAISY.begin(AudioCallback);
}

void loop() {

  if (hwSerial.available()) {
    int data = hwSerial.read();
    Serial.println(data);
  }

  delay(50);

  hwSerial.write(101);

  delay(50);
}

Still no Serial data available.

3

SOLVED by using USART3 D1 and D2 instead of USART1 on D14 and D13. I don’t know why…

4

I think the default Arduino Serial implementation (for logging etc) on Daisy already uses USART1 so you can’t also use it for a separate hardware serial instance.