Finished firmware for tower pan/tilt node. Also made the ROS node for it. Just needs to be installed on Rover.

software/ros_packages/rover_control/CMakeLists.txt

@@ -54,6 +54,7 @@ find_package(catkin REQUIRED COMPONENTS
    DriveControlMessage.msg
    DriveStatusMessage.msg
    IrisStatusMessage.msg
+   TowerPanTiltControlMessage.msg
  )
 
 ## Generate services in the 'srv' folder

software/ros_packages/rover_control/msg/TowerPanTiltControlMessage.msg

@@ -0,0 +1,4 @@
+bool should_center
+
+int16 relative_pan_adjustment
+int16 relative_tilt_adjustment

software/ros_packages/rover_control/src/tower_pan_tilt_control/pan_tilt_tester.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python
+import rospy
+import time
+
+from rover_control.msg import TowerPanTiltControlMessage
+
+DEFAULT_TOWER_PAN_TILT_CONTROL_TOPIC = "tower/control"
+
+rospy.init_node("tower_pan_tilt_tester")
+
+publisher = rospy.Publisher(DEFAULT_TOWER_PAN_TILT_CONTROL_TOPIC, TowerPanTiltControlMessage, queue_size=1)
+
+time.sleep(2)
+
+message = TowerPanTiltControlMessage()
+message.should_center = 1
+
+publisher.publish(message)
+
+time.sleep(1)
+
+message = TowerPanTiltControlMessage()
+message.relative_pan_adjustment = -100
+message.relative_tilt_adjustment = -500
+
+publisher.publish(message)

software/ros_packages/rover_control/src/tower_pan_tilt_control/tower_pan_tilt_control.py

@@ -0,0 +1,152 @@
+#!/usr/bin/env python
+#####################################
+# Imports
+#####################################
+# Python native imports
+import rospy
+
+from time import time, sleep
+
+import serial.rs485
+import minimalmodbus
+
+# Custom Imports
+from rover_control.msg import TowerPanTiltControlMessage
+
+#####################################
+# Global Variables
+#####################################
+NODE_NAME = "drive_control"
+
+DEFAULT_PORT = "/dev/ttyUSB0"
+DEFAULT_BAUD = 115200
+
+DEFAULT_INVERT = False
+
+DEFAULT_TOWER_PAN_TILT_CONTROL_TOPIC = "tower/control"
+
+NODE_ID = 1
+
+COMMUNICATIONS_TIMEOUT = 0.01  # Seconds
+
+RX_DELAY = 0.01
+TX_DELAY = 0.01
+
+DEFAULT_HERTZ = 20
+
+MODBUS_REGISTERS = {
+    "CENTER_ALL": 0,
+
+    "PAN_ADJUST_POSITIVE": 1,
+    "PAN_ADJUST_NEGATIVE": 2,
+    "TILT_ADJUST_POSITIVE": 3,
+    "TILT_ADJUST_NEGATIVE": 4
+}
+
+PAN_TILT_CONTROL_DEFAULT_MESSAGE = [
+    0,  # No centering
+    0,  # No pan positive adjustment
+    0,  # No pan negative adjustment
+    0,  # No tilt positive adjustment
+    0   # No tilt negative adjustement
+]
+
+PAN_TILT_LAST_SEEN_TIMEOUT = 2  # seconds
+
+
+#####################################
+# DriveControl Class Definition
+#####################################
+class TowerPanTiltControl(object):
+    def __init__(self):
+        rospy.init_node(NODE_NAME)
+
+        self.port = rospy.get_param("~port", DEFAULT_PORT)
+        self.baud = rospy.get_param("~baud", DEFAULT_BAUD)
+
+        self.node_id = rospy.get_param("~node_id", NODE_ID)
+
+        self.pan_tilt_control_subscriber_topic = rospy.get_param("~pan_tilt_control_topic", DEFAULT_TOWER_PAN_TILT_CONTROL_TOPIC)
+
+        self.wait_time = 1.0 / rospy.get_param("~hertz", DEFAULT_HERTZ)
+
+        self.pan_tilt_node = None
+
+        self.connect_to_pan_tilt()
+
+        self.pan_tilt_control_subscriber = \
+            rospy.Subscriber(self.pan_tilt_control_subscriber_topic, TowerPanTiltControlMessage, self.pan_tilt_control_callback)
+
+        self.pan_tilt_control_message = None
+        self.new_control_message = False
+
+        self.pan_tilt_last_seen = time()
+
+        self.run()
+
+    def __setup_minimalmodbus_for_485(self):
+        self.pan_tilt_node.serial = serial.rs485.RS485(self.port, baudrate=self.baud, timeout=COMMUNICATIONS_TIMEOUT)
+        self.pan_tilt_node.serial.rs485_mode = serial.rs485.RS485Settings(rts_level_for_rx=1, rts_level_for_tx=0,
+                                                                          delay_before_rx=RX_DELAY,
+                                                                          delay_before_tx=TX_DELAY)
+
+    def run(self):
+        self.send_startup_centering_command()
+
+        while not rospy.is_shutdown():
+            start_time = time()
+
+            try:
+                self.send_pan_tilt_control_message()
+                self.pan_tilt_last_seen = time()
+
+            except Exception, error:
+                print "Error occurred:", error
+
+            if (time() - self.pan_tilt_last_seen) > PAN_TILT_LAST_SEEN_TIMEOUT:
+                print "Tower pan/tilt not seen for", PAN_TILT_LAST_SEEN_TIMEOUT, "seconds. Exiting."
+                return  # Exit so respawn can take over
+
+            time_diff = time() - start_time
+
+            sleep(max(self.wait_time - time_diff, 0))
+
+    def connect_to_pan_tilt(self):
+        self.pan_tilt_node = minimalmodbus.Instrument(self.port, int(self.node_id))
+        self.__setup_minimalmodbus_for_485()
+
+    def send_startup_centering_command(self):
+        registers = list(PAN_TILT_CONTROL_DEFAULT_MESSAGE)
+        registers[MODBUS_REGISTERS["CENTER_ALL"]] = 1
+        self.pan_tilt_node.write_registers(0, registers)
+
+    def send_pan_tilt_control_message(self):
+        if self.new_control_message:
+            pan_tilt_control_message = self.pan_tilt_control_message  # type: TowerPanTiltControlMessage
+
+            registers = list(PAN_TILT_CONTROL_DEFAULT_MESSAGE)
+            registers[MODBUS_REGISTERS["CENTER_ALL"]] = int(pan_tilt_control_message.should_center)
+
+            if pan_tilt_control_message.relative_pan_adjustment >= 0:
+                registers[MODBUS_REGISTERS["PAN_ADJUST_POSITIVE"]] = pan_tilt_control_message.relative_pan_adjustment
+            else:
+                registers[MODBUS_REGISTERS["PAN_ADJUST_NEGATIVE"]] = -pan_tilt_control_message.relative_pan_adjustment
+
+            if pan_tilt_control_message.relative_tilt_adjustment >= 0:
+                registers[MODBUS_REGISTERS["TILT_ADJUST_POSITIVE"]] = pan_tilt_control_message.relative_tilt_adjustment
+            else:
+                registers[MODBUS_REGISTERS["TILT_ADJUST_NEGATIVE"]] = -pan_tilt_control_message.relative_tilt_adjustment
+
+            self.pan_tilt_node.write_registers(0, registers)
+
+            self.new_control_message = False
+        else:
+            self.pan_tilt_node.write_registers(0, PAN_TILT_CONTROL_DEFAULT_MESSAGE)
+
+    def pan_tilt_control_callback(self, pan_tilt_control):
+        self.pan_tilt_control_message = pan_tilt_control
+        self.new_control_message = True
+
+
+if __name__ == "__main__":
+    TowerPanTiltControl()