diff --git a/adafruit_bitmap_font/pcf.py b/adafruit_bitmap_font/pcf.py
index 7e9df42..94bf9c6 100644
--- a/adafruit_bitmap_font/pcf.py
+++ b/adafruit_bitmap_font/pcf.py
@@ -25,29 +25,29 @@
 from collections import namedtuple
 import gc
 import struct
+from micropython import const
 
 from fontio import Glyph
 from .glyph_cache import GlyphCache
 
-_PCF_PROPERTIES = 1 << 0
-_PCF_ACCELERATORS = 1 << 1
-_PCF_METRICS = 1 << 2
-_PCF_BITMAPS = 1 << 3
-_PCF_INK_METRICS = 1 << 4
-_PCF_BDF_ENCODINGS = 1 << 5
-_PCF_SWIDTHS = 1 << 6
-_PCF_GLYPH_NAMES = 1 << 7
-_PCF_BDF_ACCELERATORS = 1 << 8
-
-_PCF_DEFAULT_FORMAT = 0x00000000
-_PCF_INKBOUNDS = 0x00000200
-_PCF_ACCEL_W_INKBOUNDS = 0x00000100
-_PCF_COMPRESSED_METRICS = 0x00000100
-
-_PCF_GLYPH_PAD_MASK = 3 << 0  # See the bitmap table for explanation */
-_PCF_BYTE_MASK = 1 << 2  # If set then Most Sig Byte First */
-_PCF_BIT_MASK = 1 << 3  # If set then Most Sig Bit First */
-_PCF_SCAN_UNIT_MASK = 3 << 4
+_PCF_PROPERTIES = const(1 << 0)
+_PCF_ACCELERATORS = const(1 << 1)
+_PCF_METRICS = const(1 << 2)
+_PCF_BITMAPS = const(1 << 3)
+_PCF_INK_METRICS = const(1 << 4)
+_PCF_BDF_ENCODINGS = const(1 << 5)
+_PCF_SWIDTHS = const(1 << 6)
+_PCF_GLYPH_NAMES = const(1 << 7)
+_PCF_BDF_ACCELERATORS = const(1 << 8)
+
+_PCF_DEFAULT_FORMAT = const(0x00000000)
+_PCF_ACCEL_W_INKBOUNDS = const(0x00000100)
+_PCF_COMPRESSED_METRICS = const(0x00000100)
+
+_PCF_GLYPH_PAD_MASK = const(3 << 0)  # See the bitmap table for explanation */
+_PCF_BYTE_MASK = const(1 << 2)  # If set then Most Sig Byte First */
+_PCF_BIT_MASK = const(1 << 3)  # If set then Most Sig Bit First */
+_PCF_SCAN_UNIT_MASK = const(3 << 4)
 
 # https://fontforge.org/docs/techref/pcf-format.html
 
@@ -214,9 +214,7 @@ def _read_accelerator_tables(self):
             raise RuntimeError("Accelerator table missing")
 
         format_ = self._seek_table(accelerators)
-
         has_inkbounds = format_ & _PCF_ACCEL_W_INKBOUNDS
-        compressed_metrics = format_ & _PCF_COMPRESSED_METRICS
 
         (
             no_overlap,
@@ -231,11 +229,11 @@ def _read_accelerator_tables(self):
             font_descent,
             max_overlap,
         ) = self._read(">BBBBBBBBIII")
-        minbounds = self._read_metrics(compressed_metrics)
-        maxbounds = self._read_metrics(compressed_metrics)
+        minbounds = self._read_metrics(False)
+        maxbounds = self._read_metrics(False)
         if has_inkbounds:
-            ink_minbounds = self._read_metrics(compressed_metrics)
-            ink_maxbounds = self._read_metrics(compressed_metrics)
+            ink_minbounds = self._read_metrics(False)
+            ink_maxbounds = self._read_metrics(False)
         else:
             ink_minbounds = minbounds
             ink_maxbounds = maxbounds
diff --git a/test/displayio.py b/test/displayio.py
index d506343..7b16498 100644
--- a/test/displayio.py
+++ b/test/displayio.py
@@ -2,7 +2,9 @@
 #
 # SPDX-License-Identifier: MIT
 
+"""Implementation of minimal displayio subset for testing"""
 
+# pylint: disable=all
 class Bitmap:
     def __init__(self, width, height, color_count):
         self.width = width
diff --git a/test/fontio.py b/test/fontio.py
index 8222362..19e1062 100644
--- a/test/fontio.py
+++ b/test/fontio.py
@@ -2,6 +2,8 @@
 #
 # SPDX-License-Identifier: MIT
 
+"""Implementation of minimal fontio subset for testing"""
+
 import collections
 
 Glyph = collections.namedtuple(