Hello everyone,

I am trying to understand an issue I am seeing between my Arduino Mega 2560 and my Teensy 3.2. When I run the code below on the Arduino, it functions how I would expect it to while communicating with my VP Flowscope via modbus. However, when I implement the same code on my Teensy 3.2 I do not get anything in the serial monitor. If I unplug and re-plug in the 5V wire to the MAX485 chip I will get intermittent responses in the serial monitor though with correct data.

I am thinking this has to be a timing thing but I am new enough to these devices that I am not 100% sure the correct path to start diagnosing this. I would really appreciate some pointers.

Code:
 
#include <ModbusMaster.h>
#define MAX485_DE 3 //Enable transmit pin for MAX485 (both RE/DE tied together)

// instantiate ModbusMaster object
ModbusMaster node;

void preTransmission()
{
  digitalWrite(MAX485_DE, 1);
}

void postTransmission()
{
  digitalWrite(MAX485_DE, 0);
}

void setup()
{
  pinMode(MAX485_DE, OUTPUT);

  digitalWrite(MAX485_DE, 0);

  // Baudrate for serial monitor if you want to see responses
  while (!Serial);
  Serial.begin(38400);

  //Baudrate of modbus device is 38400
  while (!Serial1);
  Serial1.begin(38400);

  // Modbus slave ID is 9 and MAX485 is connected to RX1/TX1
  node.begin(9, Serial1);
  // Callbacks allow us to configure the RS485 transceiver correctly
  node.preTransmission(preTransmission);
  node.postTransmission(postTransmission);
}
void loop()
{

  uint8_t result;

  result = node.readHoldingRegisters(0x40, 1);
  if (result == node.ku8MBSuccess)
  {
    Serial.print("Temperature in C = ");
    Serial.println(node.getResponseBuffer(0x0)/10);
  }


    result = node.readHoldingRegisters(0x41, 1);
  if (result == node.ku8MBSuccess)
  {
    Serial.print("Temperature in F = ");
    Serial.println(node.getResponseBuffer(0x0)/10);
  }


    result = node.readHoldingRegisters(0x21, 1);
  if (result == node.ku8MBSuccess)
  {
    Serial.print("Pressure in PSI = ");
    Serial.println(node.getResponseBuffer(0x0)/10);
  }
}