diff --git a/.github/workflows/checkpr.yml b/.github/workflows/checkpr.yml
index 7b476c0..8ccdfe8 100644
--- a/.github/workflows/checkpr.yml
+++ b/.github/workflows/checkpr.yml
@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.9, "3.10", "3.11", "3.12", "3.13.0-rc.3"]
+        python-version: [3.9, "3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - uses: actions/checkout@v4
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a48e399..dfeeba4 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.9, "3.10", "3.11", "3.12", "3.13.0-rc.3"]
+        python-version: [3.9, "3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - uses: actions/checkout@v4
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 23b1a51..b7f6332 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -4,5 +4,5 @@
     "editor.formatOnSave": true,
     "modulename": "${workspaceFolderBasename}",
     "distname": "${workspaceFolderBasename}",
-    "moduleversion": "1.2.48",
+    "moduleversion": "1.2.49",
 }
\ No newline at end of file
diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index ae3b608..2180970 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,5 +1,11 @@
 # pyubx2 Release Notes
 
+### RELEASE 1.2.49
+
+ENHANCEMENTS:
+
+1. Enhance pyubx2.config_set() exception handling - addresses #173.
+
 ### RELEASE 1.2.48
 
 ENHANCEMENTS:
diff --git a/pyproject.toml b/pyproject.toml
index 77d6a05..c3265b7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,7 +7,7 @@ name = "pyubx2"
 authors = [{ name = "semuadmin", email = "semuadmin@semuconsulting.com" }]
 maintainers = [{ name = "semuadmin", email = "semuadmin@semuconsulting.com" }]
 description = "UBX protocol parser and generator"
-version = "1.2.48"
+version = "1.2.49"
 license = { file = "LICENSE" }
 readme = "README.md"
 requires-python = ">=3.9"
diff --git a/src/pyubx2/_version.py b/src/pyubx2/_version.py
index b672650..edefb1a 100644
--- a/src/pyubx2/_version.py
+++ b/src/pyubx2/_version.py
@@ -8,4 +8,4 @@
 :license: BSD 3-Clause
 """
 
-__version__ = "1.2.48"
+__version__ = "1.2.49"
diff --git a/src/pyubx2/ubxhelpers.py b/src/pyubx2/ubxhelpers.py
index 72b6830..7ef5e9f 100644
--- a/src/pyubx2/ubxhelpers.py
+++ b/src/pyubx2/ubxhelpers.py
@@ -19,6 +19,7 @@
 import pyubx2.ubxtypes_configdb as ubcdb
 import pyubx2.ubxtypes_core as ubt
 from pyubx2.ubxtypes_core import (
+    ATTTYPE,
     NMEA_PROTOCOL,
     POLL,
     RTCM3_PROTOCOL,
@@ -125,11 +126,13 @@ def attsiz(att: str) -> int:
     Helper function to return attribute size in bytes.
 
     :param str: attribute type e.g. 'U002'
-    :return: size of attribute in bytes
+    :return: size of attribute in bytes, or -1 if variable length
     :rtype: int
 
     """
 
+    if att == "CH":  # variable length
+        return -1
     return int(att[1:4])
 
 
@@ -274,11 +277,22 @@ def val2bytes(val, att: str) -> bytes:
 
     """
 
-    if att == ubt.CH:  # single variable-length string (e.g. INF-NOTICE)
-        return val.encode("utf-8", "backslashreplace")
+    try:
+        if not isinstance(val, ATTTYPE[atttyp(att)]):
+            raise TypeError(
+                f"Attribute type {att} value {val} must be {ATTTYPE[atttyp(att)]}, not {type(val)}"
+            )
+    except KeyError as err:
+        raise ube.UBXTypeError(f"Unknown attribute type {att}") from err
+
     atts = attsiz(att)
-    if atttyp(att) in ("C", "X"):  # byte or char
+    if atttyp(att) == "X":  # byte
         valb = val
+    elif atttyp(att) == "C":  # char
+        if isinstance(val, str):
+            valb = val.encode("utf-8", "backslashreplace")
+        else:  # byte
+            valb = val
     elif atttyp(att) in ("E", "L", "U"):  # unsigned integer
         valb = val.to_bytes(atts, byteorder="little", signed=False)
     elif atttyp(att) == "A":  # array of unsigned integers
@@ -289,11 +303,9 @@ def val2bytes(val, att: str) -> bytes:
     elif atttyp(att) == "I":  # signed integer
         valb = val.to_bytes(atts, byteorder="little", signed=True)
     elif att == ubt.R4:  # single precision floating point
-        valb = struct.pack("<f", val)
+        valb = struct.pack("<f", float(val))
     elif att == ubt.R8:  # double precision floating point
-        valb = struct.pack("<d", val)
-    else:
-        raise ube.UBXTypeError(f"Unknown attribute type {att}")
+        valb = struct.pack("<d", float(val))
     return valb
 
 
diff --git a/src/pyubx2/ubxmessage.py b/src/pyubx2/ubxmessage.py
index 3daaa0c..99bccf3 100644
--- a/src/pyubx2/ubxmessage.py
+++ b/src/pyubx2/ubxmessage.py
@@ -734,10 +734,11 @@ def config_set(layers: int, transaction: int, cfgData: list) -> object:
             att = ""
             (key, val) = cfgItem
             if isinstance(key, str):  # if key is a string (keyname)
-                (key, att) = cfgname2key(key)  # lookup keyID & attribute type
+                (kid, att) = cfgname2key(key)  # lookup keyID & attribute type
             else:
-                (_, att) = cfgkey2name(key)  # lookup attribute type
-            keyb = val2bytes(key, U4)
+                kid = key
+                (key, att) = cfgkey2name(key)  # lookup attribute type
+            keyb = val2bytes(kid, U4)
             valb = val2bytes(val, att)
             lis = lis + keyb + valb
 
diff --git a/src/pyubx2/ubxtypes_core.py b/src/pyubx2/ubxtypes_core.py
index 343bc99..2db452f 100644
--- a/src/pyubx2/ubxtypes_core.py
+++ b/src/pyubx2/ubxtypes_core.py
@@ -96,6 +96,18 @@
 R4 = "R004"  # Float (IEEE 754) Single Precision 4 bytes
 R8 = "R008"  # Float (IEEE 754) Double Precision 8 bytes
 
+ATTTYPE = {
+    "A": type([0, 1]),
+    "C": (type(b"0"), type("0")),
+    "E": type(0),
+    "I": type(0),
+    "L": type(0),
+    "R": (type(0), type(0.1)),
+    "U": type(0),
+    "X": type(b"0"),
+}
+"""Permissible attribute types"""
+
 # ***********************************************
 # THESE ARE THE UBX PROTOCOL CORE MESSAGE CLASSES
 # ***********************************************
diff --git a/src/pyubx2/ubxtypes_poll.py b/src/pyubx2/ubxtypes_poll.py
index c0c61d3..3689551 100644
--- a/src/pyubx2/ubxtypes_poll.py
+++ b/src/pyubx2/ubxtypes_poll.py
@@ -2,7 +2,9 @@
 UBX Protocol POLL payload definitions.
 
 THESE ARE THE PAYLOAD DEFINITIONS FOR _POLL_ MESSAGES _TO_ THE RECEIVER
-(e.g. query configuration; request monitoring, receiver management, logging or sensor fusion status).
+(e.g. query configuration; request monitoring, receiver management, 
+logging or sensor fusion status).
+
 Response payloads are defined in UBX_PAYLOADS_GET.
 
 NB: Attribute names must be unique within each message class/id
diff --git a/tests/test_configdb.py b/tests/test_configdb.py
index 9ad2d06..bed4726 100644
--- a/tests/test_configdb.py
+++ b/tests/test_configdb.py
@@ -11,7 +11,7 @@
 
 import unittest
 
-from pyubx2 import UBXMessage, SET, POLL
+from pyubx2 import UBXMessage, SET, POLL, SET_LAYER_FLASH, TXN_NONE
 from pyubx2.ubxtypes_configdb import UBX_CONFIG_DATABASE
 from tests.configdb_baseline import UBX_CONFIG_DATABASE_BASELINE
 
@@ -63,6 +63,16 @@ def testFill_CFGVALSET(self):  #  test CFG-VALSET SET constructor
         )
         self.assertEqual(str(res), EXPECTED_RESULT)
 
+    def testGOODConfigSet(self):
+        EXPECTED_RESULT = "<UBX(CFG-VALSET, version=0, ram=0, bbr=0, flash=1, action=0, reserved0=0, CFG_NAVSPG_USRDAT_ROTZ=0.0, CFG_NAVSPG_USRDAT_ROTY=0.10000000149011612)>"
+        msg = UBXMessage.config_set(
+            layers=SET_LAYER_FLASH,
+            transaction=TXN_NONE,
+            cfgData=[(0x40110069, 0), (0x40110068, 0.1)],
+        )
+        # print(msg)
+        self.assertEqual(str(msg), EXPECTED_RESULT)
+
 
 if __name__ == "__main__":
     # import sys;sys.argv = ['', 'Test.testName']
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index d223f15..a15d50a 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -28,6 +28,8 @@
     VALCKSUM,
     ERR_LOG,
     ERR_RAISE,
+    SET_LAYER_FLASH,
+    TXN_NONE,
 )
 from pyubx2.ubxhelpers import (
     cfgkey2name,
@@ -399,6 +401,32 @@ def testNMEABADEND(self):  # test truncated NMEA file
                     # print(f'"{parsed}",')
                     i += 1
 
+    def testBADConfigSet(self):  # test invalid configuration database value type
+        with self.assertRaises(TypeError):
+            UBXMessage.config_set(
+                layers=SET_LAYER_FLASH,
+                transaction=TXN_NONE,
+                cfgData=[(0x20920006, 0)],
+            )
+        with self.assertRaises(TypeError):
+            UBXMessage.config_set(
+                layers=SET_LAYER_FLASH,
+                transaction=TXN_NONE,
+                cfgData=[(0x209100E0, b"\x00")],
+            )
+        with self.assertRaises(TypeError):
+            UBXMessage.config_set(
+                layers=SET_LAYER_FLASH,
+                transaction=TXN_NONE,
+                cfgData=[(0x5005002A, b"\x00")],
+            )
+        with self.assertRaises(TypeError):
+            UBXMessage.config_set(
+                layers=SET_LAYER_FLASH,
+                transaction=TXN_NONE,
+                cfgData=[(0x40110069, 0.1), (0x40110068, "0")],
+            )
+
 
 if __name__ == "__main__":
     # import sys;sys.argv = ['', 'Test.testName']
diff --git a/tests/test_static.py b/tests/test_static.py
index 4629597..55c254e 100644
--- a/tests/test_static.py
+++ b/tests/test_static.py
@@ -17,6 +17,7 @@
 import pyubx2.ubxtypes_core as ubt
 from pyubx2 import POLL, SET, UBX_CLASSES, UBXMessage, UBXReader
 from pyubx2.ubxhelpers import (
+    attsiz,
     att2idx,
     att2name,
     bytes2val,
@@ -258,6 +259,10 @@ def testhextable(self):  # test hextable*( method)
         res = hextable(b"$GNGLL,5327.04319,S,00214.41396,E,223232.00,A,A*68\r\n", 8)
         self.assertEqual(res, EXPECTED_RESULT)
 
+    def testattsiz(self):  # test attsiz
+        self.assertEqual(attsiz("CH"), -1)
+        self.assertEqual(attsiz("C032"), 32)
+
     def testatt2idx(self):  # test att2idx
         EXPECTED_RESULT = [4, 16, 101, 0, (3, 6), 0]
         atts = ["svid_04", "gnssId_16", "cno_101", "gmsLon", "gnod_03_06", "dodgy_xx"]