From 1bcdd8e5dcb09f62212d2baffdee1ddf93f118a8 Mon Sep 17 00:00:00 2001
From: Steffen Beyer <steffen@beyer.io>
Date: Sun, 14 Jan 2024 21:11:19 +0100
Subject: [PATCH] contrib example: TCP drainage simulator with two devices

Simulates two Modbus TCP slave servers:

Digital IO (DIO) with 8 discrete inputs and 8 coils. The first two coils each
control a simulated pump. Inputs are not used.

Water level meter (WLM) returning the current water level in the input
register. It increases chronologically and decreases rapidly when one or
two pumps are active.
---
 examples/contrib/drainage_sim.py | 68 ++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100755 examples/contrib/drainage_sim.py

diff --git a/examples/contrib/drainage_sim.py b/examples/contrib/drainage_sim.py
new file mode 100755
index 000000000..8e09dd2a4
--- /dev/null
+++ b/examples/contrib/drainage_sim.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+
+# Simulates two Modbus TCP slave servers:
+#
+# Port 5020: Digital IO (DIO) with 8 discrete inputs and 8 coils. The first two coils each control
+#            a simulated pump. Inputs are not used.
+#
+# Port 5021: Water level meter (WLM) returning the current water level in the input register. It
+#            increases chronologically and decreases rapidly when one or two pumps are active.
+
+import asyncio
+import logging
+from datetime import datetime
+
+from pymodbus.datastore import ModbusSequentialDataBlock, ModbusSlaveContext, ModbusServerContext
+from pymodbus.server import StartAsyncTcpServer
+
+INITIAL_WATER_LEVEL = 300
+WATER_INFLOW = 1
+PUMP_OUTFLOW = 8
+
+logging.basicConfig(level = logging.INFO)
+
+dio_di = ModbusSequentialDataBlock(1, [False] * 8)
+dio_co = ModbusSequentialDataBlock(1, [False] * 8)
+dio_context = ModbusSlaveContext(di = dio_di, co = dio_co)
+wlm_ir = ModbusSequentialDataBlock(1, [INITIAL_WATER_LEVEL])
+wlm_context = ModbusSlaveContext(ir = wlm_ir)
+
+async def update():
+    while True:
+        await asyncio.sleep(1)
+
+        # Update water level based on DIO output values (simulating pumps)
+        water_level = wlm_ir.getValues(1, 1)[0]
+        dio_outputs = dio_co.getValues(1, 2)
+
+        water_level += WATER_INFLOW
+        water_level -= (int(dio_outputs[0]) + int(dio_outputs[1])) * PUMP_OUTFLOW
+        water_level = max(0, min(INITIAL_WATER_LEVEL * 10, water_level))
+        wlm_ir.setValues(1, [water_level])
+
+async def log():
+    while True:
+        await asyncio.sleep(10)
+
+        dio_outputs = dio_co.getValues(1, 8)
+        wlm_level = wlm_ir.getValues(1, 1)[0]
+
+        logging.info(f"{datetime.now()}: WLM water level: {wlm_level}, DIO outputs: {dio_outputs}")
+
+async def run():
+    ctx = ModbusServerContext(slaves = dio_context)
+    dio_server = asyncio.create_task(StartAsyncTcpServer(context = ctx, address = ("0.0.0.0", 5020)))
+    logging.info("Initialising slave server DIO on port 5020")
+
+    ctx = ModbusServerContext(slaves = wlm_context)
+    wlm_server = asyncio.create_task(StartAsyncTcpServer(context = ctx, address = ("0.0.0.0", 5021)))
+    logging.info("Initialising slave server WLM on port 5021")
+
+    update_task = asyncio.create_task(update())
+    logging_task = asyncio.create_task(log())
+
+    logging.info("Init complete")
+    await asyncio.gather(dio_server, wlm_server, update_task, logging_task)
+
+if __name__ == "__main__":
+    asyncio.run(run(), debug=True)