Adds motor encoder demo code

sampleCode/encoder_demo.py

@@ -0,0 +1,58 @@
+# UKMARS Gemini Encoder Demo
+# Oct 29 2025
+# Prints the left and right motor encoder values
+
+from machine import Pin
+from time import sleep
+
+# Define pins
+# You may need to swap the numbers if one encoder is negative when going forward
+left_a = Pin(8, Pin.IN, Pin.PULL_UP)
+left_b = Pin(9, Pin.IN, Pin.PULL_UP)
+
+right_a = Pin(7, Pin.IN, Pin.PULL_UP)
+right_b = Pin(6, Pin.IN, Pin.PULL_UP)
+
+
+# Global state
+last_left_a = left_a.value()
+last_right_a = left_a.value()
+
+left_counts = 0
+right_counts = 0
+
+def left_encoder_callback(pin):
+    global left_counts, last_left_a
+    a = left_a.value()
+    b = left_b.value()
+
+    if a != last_left_a:
+        # Check direction based on B when A changes
+        if a == b:
+            left_counts -= 1
+        else:
+            left_counts += 1
+        last_left_a = a
+
+def right_encoder_callback(pin):
+    global right_counts, last_right_a
+    a = right_a.value()
+    b = right_b.value()
+
+    if a != last_right_a:
+        # Check direction based on B when A changes
+        if a == b:
+            right_counts -= 1
+        else:
+            right_counts += 1
+        last_right_a = a
+
+
+# Attach interrupts
+left_a.irq(trigger=Pin.IRQ_RISING | Pin.IRQ_FALLING, handler=left_encoder_callback)
+right_a.irq(trigger=Pin.IRQ_RISING | Pin.IRQ_FALLING, handler=right_encoder_callback)
+
+# Main loop
+while True:
+    print(f"Left: {left_counts} Right: {right_counts}")
+    sleep(0.1)