Add limit switch code

limits.py

@@ -2,21 +2,30 @@ import time
 import sys
 import RPi.GPIO as GPIO
 
+
+PATH_OPEN = 0
+PATH_BLOCKED = 1
+LIMIT_LOWER_RIGHT = 19
+LIMIT_LOWER_LEFT = 20
+LIMIT_UPPER_RIGHT = 21
+
+
 GPIO.setmode(GPIO.BCM)
 
-GPIO.setup(19, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(LIMIT_LOWER_RIGHT, GPIO.IN, pull_up_down=GPIO.PUD_UP)
-GPIO.setup(20, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(LIMIT_LOWER_LEFT, GPIO.IN, pull_up_down=GPIO.PUD_UP)
-GPIO.setup(21, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(LIMIT_UPPER_RIGHT, GPIO.IN, pull_up_down=GPIO.PUD_UP)
 
-# 1 = optical path blocked, 0 = open
+
+# True = optical path blocked, False = open
 
 def test():
     while True:
         try:
             print(
-                'GPIO19:', GPIO.input(19),
+                'Lower Right (GPIO19):', GPIO.input(LIMIT_LOWER_RIGHT) == PATH_BLOCKED,
-                'GPIO20:', GPIO.input(20),
+                '| Lower Left (GPIO20):', GPIO.input(LIMIT_LOWER_LEFT) == PATH_BLOCKED,
-                'GPIO21:', GPIO.input(21),
+                '| Upper Right (GPIO21):', GPIO.input(LIMIT_UPPER_RIGHT) == PATH_BLOCKED,
             )
 
             time.sleep(1)

main.py

@@ -12,9 +12,11 @@ import aiomqtt
 import serial
 import glob
 import time
+import RPi.GPIO as GPIO
 
 import dyn4
 import relays
+import limits
 
 ENCODER_PPR = 65536
 
@@ -24,6 +26,13 @@ dmm1 = None
 dmm2 = None
 
 
+# 2025-10-24 facts:
+#    Motor1 is left
+#    Motor2 is right
+#    Positive RPM moves the crosshead down
+#    Negative RPM moves the crosshead up
+
+
 MOTOR_EN1 = 1
 MOTOR_EN2 = 2
 DISABLED = None
@@ -257,6 +266,27 @@ async def monitor_dyn4():
                 logging.info('Pos difference: %s, rev1: %s, rev2: %s, scaler1: %s, scaler2: %s, target: %s, rpm1: %s, rpm2: %s',
                     difference, rev1, rev2, motor1_scaler, motor2_scaler, RPM_TARGET, motor1_rpm, motor2_rpm)
 
+
+        # check limit switches
+        if ONE_MOTOR:
+            pass
+        else:
+            GOING_DOWNWARD = motor1_rpm > 0 or motor2_rpm > 0
+            GOING_UPWARD = motor1_rpm < 0 or motor2_rpm < 0
+
+            if GOING_DOWNWARD:
+                if GPIO.input(limits.LIMIT_LOWER_RIGHT) == limits.PATH_BLOCKED or GPIO.input(limits.LIMIT_LOWER_LEFT) == limits.PATH_BLOCKED:
+                    motor1_rpm = 0
+                    motor2_rpm = 0
+                    logging.info('Lower limit switch hit, preventing downward travel.')
+
+            if GOING_UPWARD:
+                if GPIO.input(limits.LIMIT_UPPER_RIGHT) == limits.PATH_BLOCKED:
+                    motor1_rpm = 0
+                    motor2_rpm = 0
+                    logging.info('Upper limit switch hit, preventing upward travel.')
+
+
         if ONE_MOTOR:
             logging.debug('Setting motor1: %s', motor1_rpm)
             dmm1.set_speed(motor1_rpm)