From d8f3ad17585ad29f319a1d9f2b1c8d6b0c3118df Mon Sep 17 00:00:00 2001
From: Eva Lott <evalott100@gmail.com>
Date: Wed, 11 Dec 2024 11:14:29 +0000
Subject: [PATCH] added tango `RDS` alarm parameters and EPICS v4 hysteresis

---
 src/event_model/documents/event_descriptor.py | 35 ++++++++++++++++++-
 src/event_model/schemas/event_descriptor.json | 31 +++++++++++++++-
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/src/event_model/documents/event_descriptor.py b/src/event_model/documents/event_descriptor.py
index d9cb89084..b92966981 100644
--- a/src/event_model/documents/event_descriptor.py
+++ b/src/event_model/documents/event_descriptor.py
@@ -7,6 +7,35 @@
 Dtype = Literal["string", "number", "array", "boolean", "integer"]
 
 
+class RdsRange(TypedDict):
+    """RDS (Read different than set) parameters range.
+
+
+    https://tango-controls.readthedocs.io/en/latest/development/device-api/attribute-alarms.html#the-read-different-than-set-rds-alarm
+    """
+
+    time_difference: Annotated[
+        float,
+        Field(
+            description=(
+                "ms since last update to fail after if set point and "
+                "read point are not within `value_difference` of each other."
+            )
+        ),
+    ]
+    value_difference: NotRequired[
+        Annotated[
+            float,
+            Field(
+                description=(
+                    "Allowed difference in value between set point and read point "
+                    "after `time_difference`."
+                )
+            ),
+        ]
+    ]
+
+
 class LimitsRange(TypedDict):
     low: Optional[float]
     high: Optional[float]
@@ -14,14 +43,18 @@ class LimitsRange(TypedDict):
 
 class Limits(TypedDict):
     """
-    Epics limits:
+    Epics and tango limits:
     see 3.4.1 https://epics.anl.gov/base/R3-14/12-docs/AppDevGuide/node4.html
+    and
+    https://tango-controls.readthedocs.io/en/latest/development/device-api/attribute-alarms.html
     """
 
     control: NotRequired[Annotated[LimitsRange, Field(description="Control limits.")]]
     display: NotRequired[Annotated[LimitsRange, Field(description="Display limits.")]]
     warning: NotRequired[Annotated[LimitsRange, Field(description="Warning limits.")]]
     alarm: NotRequired[Annotated[LimitsRange, Field(description="Alarm limits.")]]
+    hysteresis: NotRequired[Annotated[float, Field(description="Hysteresis.")]]
+    rds: NotRequired[Annotated[RdsRange, Field(description="RDS parameters.")]]
 
 
 _ConstrainedDtype = Annotated[
diff --git a/src/event_model/schemas/event_descriptor.json b/src/event_model/schemas/event_descriptor.json
index ea7ef71ed..02338d088 100644
--- a/src/event_model/schemas/event_descriptor.json
+++ b/src/event_model/schemas/event_descriptor.json
@@ -150,7 +150,7 @@
         },
         "Limits": {
             "title": "Limits",
-            "description": "Epics limits:\nsee 3.4.1 https://epics.anl.gov/base/R3-14/12-docs/AppDevGuide/node4.html",
+            "description": "Epics and tango limits:\nsee 3.4.1 https://epics.anl.gov/base/R3-14/12-docs/AppDevGuide/node4.html\nand\nhttps://tango-controls.readthedocs.io/en/latest/development/device-api/attribute-alarms.html",
             "type": "object",
             "properties": {
                 "alarm": {
@@ -165,6 +165,15 @@
                     "description": "Display limits.",
                     "$ref": "#/$defs/LimitsRange"
                 },
+                "hysteresis": {
+                    "title": "Hysteresis",
+                    "description": "Hysteresis.",
+                    "type": "number"
+                },
+                "rds": {
+                    "description": "RDS parameters.",
+                    "$ref": "#/$defs/RdsRange"
+                },
                 "warning": {
                     "description": "Warning limits.",
                     "$ref": "#/$defs/LimitsRange"
@@ -224,6 +233,26 @@
                 }
             }
         },
+        "RdsRange": {
+            "title": "RdsRange",
+            "description": "RDS (Read different than set) parameters range.\n\n\nhttps://tango-controls.readthedocs.io/en/latest/development/device-api/attribute-alarms.html#the-read-different-than-set-rds-alarm",
+            "type": "object",
+            "properties": {
+                "time_difference": {
+                    "title": "Time Difference",
+                    "description": "ms since last update to fail after if set point and read point are not within `value_difference` of each other.",
+                    "type": "number"
+                },
+                "value_difference": {
+                    "title": "Value Difference",
+                    "description": "Allowed difference in value between set point and read point after `time_difference`.",
+                    "type": "number"
+                }
+            },
+            "required": [
+                "time_difference"
+            ]
+        },
         "DataType": {
             "title": "DataType",
             "patternProperties": {