rotary table driven by stepper motor controlled by 2 Arduino's

[metric_taper]

Encoder Arduino code using Arduino Nano


#include <SPI.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Wire.h>


#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 32 // OLED display height, in pixels




// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET 4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


const byte interrupt = 2;
const byte interruptB = 3;
const int encoder1PinA = 2; // encoder channel A,B (interupt pins)
const int encoder1PinB = 3;
float Pos1deg = 0;




volatile float encoder1Pos = 0; //ticks of encoder will change, initial number is zero




void setup()
{
Wire.setClock(400000);
// Serial.begin(9600);
if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x32
//Serial.println(F("SSD1306 allocation failed"));
for (;; // Don't proceed, loop forever
}
attachInterrupt(0, runEncoder1, RISING ); // encoder pin on interrupt 0 >>(pin 2 on arduino)


}


void loop()
{


float Pos1;
uint8_t oldSREG = SREG;


cli();
Pos1 = encoder1Pos;
SREG = oldSREG;
static int oldPos1;
if (Pos1 != oldPos1) {
oldPos1 = Pos1;
}

I thought there would be an ISR routine for the attachInterrupt. Am I missing something in how arduino code works?