python example use of the busy record

demonstration of client use of the EPICS busy record

documentation/busyExample.py

@@ -0,0 +1,140 @@
+#!/usr/bin/env python
+
+"""
+demonstration of client use of the EPICS busy record
+
+Uses these records from a running synApps XXX (style) IOC:
+
+======  =================  ==================
+record  PV used here       URL
+======  =================  ==================
+busy    ``xxx:mybusy``     https://github.com/epics-modules/busy
+motor   ``xxx:m1``         https://github.com/epics-modules/motor
+swait   ``xxx:userCalc1``  https://github.com/epics-modules/calc
+======  =================  ==================
+
+Description:
+
+#. Run this python program in a command shell.
+#. From a GUI or other client do these things:
+#. set the busy record.VAL to 1
+#. watch the motor record .VAL, .RBV, and .DMOV fields
+#. watch the swait record .CALC and .VAL fields
+#. wait for busy record to return to 0
+#. To end the python program orderly:
+#. set the swait.CALC field to 0 (changes the calculation)
+#. set the swait.PROC field to 1 (recalculate a new value)
+#. To end the python program abruptly, press ^C in the terminal
+
+EXAMPLE::
+
+    user@localhost ~ $ ./busyExample.py 
+    INFO:root:starting the process in a thread
+    INFO:root:process() start
+    (0.0, 0.1270313572899977)
+    (2.1, 0.9285114824139773)
+    (4.2, 0.578789959563592)
+    (6.3, 0.46387426565957124)
+    (8.4, 0.30080109864957655)
+    INFO:root:process() complete
+    INFO:root:starting the process in a thread
+    INFO:root:process() start
+    (0.0, 0.3134508278019379)
+    (2.1, 0.7051956969558252)
+    (4.2, 0.2409094377050431)
+    INFO:root:process() interrupted
+    INFO:root:process() complete
+    INFO:root:starting the process in a thread
+    INFO:root:process() start
+    (0.0, 0.5009384298466468)
+    (2.1, 0.11929503318837263)
+    (4.2, 0.06889448386358435)
+    (6.3, 0.8060425726710918)
+    (8.4, 0.8368200198367285)
+    INFO:root:process() complete
+
+
+"""
+
+
+import epics        # http://cars9.uchicago.edu/software/python/pyepics3
+import logging
+import threading
+
+logging.basicConfig(level=logging.INFO) 
+
+PREFIX = "xxx:"     # xxx: is from a synApps xxx IOC
+BUSY_PV = PREFIX + "mybusy"     # busy record
+MOTOR_PV = PREFIX + "m1"        # motor record
+CALC_PV = PREFIX + "userCalc1"  # swait record
+
+
+class Demonstrator(object):
+
+    def __init__(self, busy_pv_name, motor_pv_name, calc_pv_name):
+        self.busy = epics.PV(busy_pv_name)
+
+        # motor: the independent variable
+        self.motor = epics.Motor(motor_pv_name)
+
+        # calc: the detector signal
+        self.calc = epics.PV(calc_pv_name)
+        self.calc_proc = epics.PV(calc_pv_name + ".PROC")
+        epics.caput(calc_pv_name+".CALC", "RNDM")   # report random numbers
+        self.calc_proc.put(1)   # get a new value
+
+        self.cb_index = None
+        self.processing = False
+
+        # arbitrary choices for a demo program
+        self.num_steps = 5
+        self.step_size = 2.1
+        self.origin = 0
+
+    def monitor(self):
+        if self.cb_index is None:
+            self.cb_index = self.busy.add_callback(self.busy_callback)
+
+    def unmonitor(self):
+        if self.cb_index is not None:
+            self.busy.remove_callback(self.cb_index)
+            self.cb_index = None
+
+    def busy_callback(self, *args, **kwargs):
+        if not self.processing and self.busy.value == 1:
+            logging.info("starting the process in a thread")
+            thread = threading.Thread(target=self.process)
+            thread.start()
+        # else:
+        #     for k, v in sorted(kwargs.items()):
+        #         print(k, v)
+
+    def process(self):
+        if self.processing:
+            return
+        logging.info("process() start")
+        self.processing = True
+        self.motor.move(self.origin, wait=True)
+        for step_number in range(self.num_steps):
+            if self.busy.value != 1:
+                logging.info("process() interrupted")
+                break
+            target = self.origin + step_number * self.step_size
+            self.motor.move(target, wait=True)
+            self.calc_proc.put(1)   # get a new value
+            print(self.motor.readback, self.calc.value)
+        self.busy.put(0)
+        self.processing = False
+        logging.info("process() complete")
+
+
+def main():
+    process = Demonstrator(BUSY_PV, MOTOR_PV, CALC_PV)
+    process.monitor()
+    while process.calc.value != 0:
+        pass
+    process.unmonitor()     # not really needed, we're quitting anyway
+
+
+if __name__ == "__main__":
+    main()