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fix(envea): correct serial read to prevent spurious spikes

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- Replace readline() with read(32) to avoid truncation at 0x0A bytes
- Add reset_input_buffer() to clear stale data before each read
- Add initial read to consume echo/acknowledgment from sensor
- Add frame header validation (0xFF 0x02) to reject invalid data
- Add delays to allow sensor response time

Fixes issue where NO2/H2S sensors showed random spikes due to
binary data containing newline characters being misinterpreted.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
PaulVua
2026-01-23 17:20:04 +01:00
parent 91a4e7c841
commit eeaaeca4a7
1 changed files with 43 additions and 26 deletions
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69
envea/read_value_v2.py
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@@ -105,39 +105,56 @@ try:
serial_connection = serial_connections[name]
try:
debug_print(f"Reading from {name}...")
# Flush input buffer to clear any stale data
serial_connection.reset_input_buffer()
# Send command to sensor
command = b"\xFF\x02\x13\x30\x01\x02\x03\x04\x05\x06\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x12\xAF\x88\x03"
serial_connection.write(command)
debug_print(f" → Sent command: {command.hex()}")
# Wait for sensor response
time.sleep(0.5)
# Read fixed number of bytes (not readline which stops at 0x0A)
# First read to consume any echo/acknowledgment
initial_data = serial_connection.read(serial_connection.in_waiting or 1)
debug_print(f" ← Initial read: {len(initial_data)} bytes")
# Small delay then read the actual response
time.sleep(0.1)
data_envea = serial_connection.read(32) # Read fixed 32 bytes
debug_print(f" ← Received {len(data_envea)} bytes: {data_envea.hex() if data_envea else 'empty'}")
# Read response
data_envea = serial_connection.readline()
debug_print(f" ← Received {len(data_envea)} bytes: {data_envea.hex()}")
# Validate frame: should start with 0xFF 0x02 and have at least 20 bytes
if len(data_envea) >= 20:
byte_20 = data_envea[19]
raw_value = byte_20
calculated_value = byte_20 * coefficient
debug_print(f" → Byte 20 value: {raw_value} (0x{raw_value:02X})")
debug_print(f" → Calculated value: {raw_value} × {coefficient} = {calculated_value}")
if name == "h2s":
data_h2s = calculated_value
elif name == "no2":
data_no2 = calculated_value
elif name == "o3":
data_o3 = calculated_value
elif name == "co":
data_co = calculated_value
elif name == "nh3":
data_nh3 = calculated_value
elif name == "so2":
data_so2 = calculated_value
debug_print(f" ✓ {name.upper()} = {calculated_value}")
# Check frame header (0xFF 0x02 expected for valid CAIRSENS response)
if data_envea[0] == 0xFF and data_envea[1] == 0x02:
byte_20 = data_envea[19]
raw_value = byte_20
calculated_value = byte_20 * coefficient
debug_print(f" → Byte 20 value: {raw_value} (0x{raw_value:02X})")
debug_print(f" → Calculated value: {raw_value} × {coefficient} = {calculated_value}")
if name == "h2s":
data_h2s = calculated_value
elif name == "no2":
data_no2 = calculated_value
elif name == "o3":
data_o3 = calculated_value
elif name == "co":
data_co = calculated_value
elif name == "nh3":
data_nh3 = calculated_value
elif name == "so2":
data_so2 = calculated_value
debug_print(f" ✓ {name.upper()} = {calculated_value}")
else:
debug_print(f" ✗ Invalid frame header: expected FF 02, got {data_envea[0]:02X} {data_envea[1]:02X}")
else:
debug_print(f" ✗ Response too short (expected ≥20 bytes)")
debug_print(f" ✗ Response too short ({len(data_envea)} bytes, expected ≥20)")
except serial.SerialException as e:
debug_print(f"✗ Error communicating with {name}: {e}")