Interfacing Arduino MEGA with Fluorometer - Serial Connection Problem

Hi everyone,

I am trying to interface my MEGA with a WetLabs Fluorometer (Link Below)

The WetLabs Fluorometer spits out serial data every second at 19200 baud and 12 bit resolution. I can connect the fluorometer to my computer using a terminal emulator and get a nice output at 19200 baud (see attached picture), but can’t seem to catch the data coming in through the arduino. I am using a MAX3232 serial to ttl converter module and have the tx/rx attached to MEGA correctly (I troubleshot by making a serial loop through my computer and was able to communicate from the serial window in Arduino software program and through another serial window using a separate serial output through the ttl converter and back into my computer form the arduino).

The eventual goal is to log the data coming in through the fluorometer on an SD card but for now I just want to get the data into the buffer correctly and be able to have a variable string that I can send to the SD card. The code below is attempting to gather the incoming serial data from the fluorometer and spit it out to the serial monitor, but I don’t get anything coming in at all. The serial monitor is just blank and is not picking up the incoming serial data. Thanks so much for any suggestions in altering my code or hardware configuration to talk to this fluorometer.

Fluorometer rx/tx connected to Serial 2 (16 & 17). Serial/ttl converter powered by 3.3v from board. Fluorometer powered externally at 12v.


void setup() {
// initialize both serial ports:

void loop() {
if (Serial2.available()) { // If Serial data is available, store it as discrete data point
int data =; // Read incoming data
delay(750); // Allow time for buffer to fill
Serial.write(data); // Print fluorometer data to serial monitor

Screen Shot 2015-05-19 at 12.25.54 PM.png

  delay(750);                            // Allow time for buffer to fill

Complete and utter nonsense. No wonder you are loosing serial data.

Hi Paul,

I've tried it without the delay and am still getting nothing. Do you think the serial/ttl converter can't handle 19200 baud? It seems like that should be completely fine... Is there any other parameters that I am forgetting to add that may be limiting the serial connection? Thanks for any help troubleshooting