1 Bitfield Utilities in C
2 ===========================
4 This is a C library with functions to help encode and decode Controller Area
5 Network (CAN) message payloads or other bitfields.
7 The header files contain complete function documentation, but to get you
8 started, here are examples using the API:
10 ## Bitfield Manipulation
12 uint8_t data[4] = {0x12, 0x34, 0x56, 0x78};
13 uint8_t result = get_byte(data, sizeof(data), 0);
15 result = get_nibble(data, sizeof(data), 0);
17 bool success = copy_bits_right_aligned(data, 4, 4, 12, result, 4)
22 ## 8 Byte Bitfield Decoding
24 uint64_t data = 0x8000000000000000;
25 uint64_t result = get_bit_field(data, 0, 1, false);
28 data = 0x0402574d555a0401;
29 result = get_bit_field(data, 16, 32, false);
30 // result = 0x574d555a;
32 data = 0x00000000F34DFCFF;
33 result = eightbyte_get_byte(data, 0, false);
36 result = eightbyte_get_byte(data, 4, false);
39 result = eightbyte_get_nibble(data, 10, false);
42 ## 8 Byte Bitfield Encoding
45 fail_unless(set_bit_field(&data, 1, 0, 1));
46 uint64_t result = get_bit_field(data, 0, 1, false);
47 ck_assert_int_eq(result, 0x1);
49 TODO setting bit fields is just copying
51 ## CAN Signal Encoding
53 The library supports encoding floating point CAN signals as well as booleans
54 into a uint64_t payload.
56 uint64_t payload = bitfield_encode_float(1, 1, 3, 1, 0)
57 // payload == 0x1000000000000000
59 payload = bitfield_encode_bool(true, 1, 3);
60 // payload == 0x1000000000000000
62 ## CAN Signal Decoding
64 The library supports parsing floating point CAN signals as well as booleans.
66 uint64_t payload = 0xeb00000000000000;
67 float float_result = bitfield_parse_float(payload,
69 4, // width of the signal's field
70 1001.0, // transformation factor for the signal value
71 -30000.0); // transformation offset for the signal value
72 // float_result == -19990.0
74 bool bool_result = bitfield_parse_bool(payload,
76 1, // width of the signal's field
77 1.0, // transformation factor for the signal value
78 0); // transformation offset for the signal value
79 // bool_result == true
83 The library includes a test suite that uses the `check` C unit test library. It
84 requires the unit testing library `check`.
90 Chris Peplin cpeplin@ford.com
94 Copyright (c) 2013 Ford Motor Company
96 Licensed under the BSD license.