fix: flush stale bytes before each shared poll + increase lock timeout (v1.0.9)

Two fixes for shared connection mode (issue #351):

1. Pre-poll buffer flush: after acquiring the hub lock, drain any bytes left in
   the adapter's TCP receive buffer before starting reads. With a persistent
   shared connection, late RS485 responses from the previous slave's poll can
   arrive after the lock is released and sit in the buffer until the next slave
   picks them up, causing transaction ID mismatches. Flushing before each
   locked poll cycle prevents this.

2. SHARED_LOCK_TIMEOUT increased from 30s to 60s: the 3000-range register
   block has no skip-on-failure caching, so each failing chunk costs a full
   TCP timeout (10s). Multiple failing chunks can push poll time past 30s,
   triggering spurious lock timeout warnings and skipped polls on the other
   coordinator. 60s accommodates realistic worst-case poll times.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 0xAHA

README.md

@@ -3,7 +3,7 @@
 # Growatt Modbus Integration for Home Assistant ☀️
 
 ![HACS Badge](https://img.shields.io/badge/HACS-Custom-orange.svg)
-![Version](https://img.shields.io/badge/Version-1.0.8-blue.svg)
+![Version](https://img.shields.io/badge/Version-1.0.9-blue.svg)
 [![GitHub Issues](https://img.shields.io/github/issues/0xAHA/Growatt_ModbusTCP.svg)](https://github.com/0xAHA/Growatt_ModbusTCP/issues)
 [![GitHub Stars](https://img.shields.io/github/stars/0xAHA/Growatt_ModbusTCP.svg?style=social)](https://github.com/0xAHA/Growatt_ModbusTCP)
 

RELEASENOTES.md

@@ -4,6 +4,26 @@
 
 ---
 
+## v1.0.9
+
+Issues: #351
+
+- **Fix: Remaining transaction ID mismatches in shared connection mode (#351):**
+  With a persistent shared TCP connection, late RS485 responses from a previous slave's poll
+  could arrive in the adapter's buffer after the lock was released. When the next slave acquired
+  the lock and started reading, those stale bytes produced transaction ID mismatches
+  ("request ask for id=X but got id=Y"). Fix: the receive buffer is now flushed at the start
+  of every locked poll cycle, not just on reconnect.
+
+- **Fix: Shared connection lock timeout with slow/failing register blocks (#351):**
+  The 3000-range register block does not have the same skip-on-failure caching as the VPP 31000
+  range. A failing 3000-range chunk costs a full TCP timeout (10s) per chunk, and multiple
+  failing chunks could push the total poll time past the 30s lock timeout, causing the other
+  coordinator to log "Shared Modbus connection busy (lock timeout 30s)" and skip its poll.
+  `SHARED_LOCK_TIMEOUT` increased from 30s to 60s to accommodate realistic worst-case poll times.
+
+---
+
 ## v1.0.8
 
 Issues: #351

custom_components/growatt_modbus/const.py

@@ -65,7 +65,7 @@
 # When two TCP entries share the same host:port, a single ModbusTcpClient is
 # reused with a threading.Lock to serialize reads and prevent RS485 cross-talk.
 # ============================================================================
-SHARED_LOCK_TIMEOUT = 30       # seconds to wait for shared bus lock before giving up
+SHARED_LOCK_TIMEOUT = 60       # seconds to wait for shared bus lock before giving up
 DEFAULT_INTER_SLAVE_DELAY_MS = 50  # ms pause after each slave poll to let RS485 bus settle
 
 # ============================================================================

custom_components/growatt_modbus/coordinator.py

@@ -933,6 +933,11 @@ def _fetch_data_shared(self) -> GrowattData | None:
                 )
                 return None
 
+            # Flush any stale bytes left in the adapter's TCP buffer by the
+            # previous slave's poll (late RS485 responses that arrived after the
+            # lock was released cause transaction ID mismatches on this slave's reads).
+            hub._flush_receive_buffer()
+
             self._client._battery_voltage_range = self.config_entry.options.get(
                 "battery_voltage_range", "Auto-detect"
             )

custom_components/growatt_modbus/manifest.json

@@ -12,5 +12,5 @@
     "pymodbus>=3.0.0",
     "pyserial>=3.4"
   ],
-  "version": "1.0.8"
+  "version": "1.0.9"
 }