add a method to convert binary content to UF2

will be used in concatenate in order to write .uf2 files

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

gp2040ce_bintools/builder.py

@@ -6,6 +6,7 @@ SPDX-License-Identifier: MIT
 import argparse
 import copy
 import logging
+import struct
 from typing import Optional
 
 from google.protobuf.message import Message
@@ -21,6 +22,11 @@ logger = logging.getLogger(__name__)
 GP2040CE_START_ADDRESS = 0x10000000
 GP2040CE_SIZE = 2 * 1024 * 1024
 
+UF2_FAMILY_ID = 0xE48BFF56
+UF2_MAGIC_FIRST = 0x0A324655
+UF2_MAGIC_SECOND = 0x9E5D5157
+UF2_MAGIC_FINAL = 0x0AB16F30
+
 
 #################
 # LIBRARY ITEMS #
@@ -106,6 +112,38 @@ def concatenate_firmware_and_storage_files(firmware_filename: str,
         write(endpoint_out, endpoint_in, GP2040CE_START_ADDRESS, bytes(new_binary))
 
 
+def convert_binary_to_uf2(binary: bytearray) -> bytearray:
+    """Convert a GP2040-CE binary payload to Microsoft's UF2 format.
+
+    https://github.com/microsoft/uf2/tree/master#overview
+
+    Args:
+        binary: bytearray content to convert to a UF2 payload
+    Returns:
+        the content in UF2 format
+    """
+    size = len(binary)
+    blocks = (len(binary) // 256) + 1 if len(binary) % 256 else len(binary) // 256
+    uf2 = bytearray()
+
+    index = 0
+    while index < size:
+        pad_count = 476 - len(binary[index:index+256])
+        uf2 += struct.pack('<LLLLLLLL',
+                           UF2_MAGIC_FIRST,                                 # first magic number
+                           UF2_MAGIC_SECOND,                                # second magic number
+                           0x00002000,                                      # familyID present
+                           0x10000000 + index,                              # address to write to
+                           256,                                             # bytes to write in this block
+                           index // 256,                                    # sequential block number
+                           blocks,                                          # total number of blocks
+                           UF2_FAMILY_ID)                                   # family ID
+        uf2 += binary[index:index+256] + bytearray(b'\x00' * pad_count)     # content
+        uf2 += struct.pack('<L', UF2_MAGIC_FINAL)                           # final magic number
+        index += 256
+    return uf2
+
+
 def get_gp2040ce_from_usb() -> tuple[bytes, object, object]:
     """Read the firmware + config sections from a USB device.
 

tests/conftest.py

@@ -52,9 +52,22 @@ def storage_dump():
 
 @pytest.fixture
 def whole_board_dump():
-    """Read in a test whole board dump file of a GP2040-CE board."""
+    """Read in a test whole board dump file of a GP2040-CE board.
+
+    NOTE: this is from a 16 MB flash because I used an ABB for this test.
+    """
     filename = os.path.join(HERE, 'test-files', 'test-whole-board.bin')
     with open(filename, 'rb') as file:
         content = file.read()
 
     yield content
+
+
+@pytest.fixture
+def whole_board_with_board_config_dump():
+    """Read in a test whole board dump file of a GP2040-CE board plus board config."""
+    filename = os.path.join(HERE, 'test-files', 'test-whole-board-with-board-config.bin')
+    with open(filename, 'rb') as file:
+        content = file.read()
+
+    yield content

tests/test_builder.py

@@ -12,9 +12,10 @@ from decorator import decorator
 
 from gp2040ce_bintools import get_config_pb2
 from gp2040ce_bintools.builder import (FirmwareLengthError, combine_firmware_and_config,
-                                       concatenate_firmware_and_storage_files, get_gp2040ce_from_usb,
+                                       concatenate_firmware_and_storage_files, convert_binary_to_uf2,
-                                       pad_binary_up_to_board_config, pad_binary_up_to_user_config,
+                                       get_gp2040ce_from_usb, pad_binary_up_to_board_config,
-                                       replace_config_in_binary, write_new_config_to_filename, write_new_config_to_usb)
+                                       pad_binary_up_to_user_config, replace_config_in_binary,
+                                       write_new_config_to_filename, write_new_config_to_usb)
 from gp2040ce_bintools.storage import (get_board_storage_section, get_config, get_config_footer,
                                        get_user_storage_section, serialize_config_with_footer)
 
@@ -75,6 +76,15 @@ def test_concatenate_both_configs_to_file(tmp_path):
     assert footer_size == 3309
 
 
+def test_convert_binary_to_uf2(whole_board_with_board_config_dump):
+    """Do some sanity checks in the attempt to convert a binary to a UF2."""
+    uf2 = convert_binary_to_uf2(whole_board_with_board_config_dump)
+    assert len(uf2) == 4194304                              # binary is 8192 256 byte chunks, UF2 is 512 b per chunk
+    assert uf2[0:4] == b'\x55\x46\x32\x0a' == b'UF2\n'      # proper magic
+    assert uf2[8:12] == bytearray(b'\x00\x20\x00\x00')      # family ID set
+    assert uf2[524:528] == bytearray(b'\x00\x01\x00\x10')   # address to write the second chunk
+
+
 @with_pb2s
 def test_concatenate_user_json_to_file(tmp_path):
     """Test that we write a file with firmware + JSON user config as expected."""