This is a C library with functions to help encode and decode Controller Area Network (CAN) message payloads or other bitfields.
The header files contain complete function documentation, but to get you started, here are examples using the API:
The bitfields are stored in uint8_t[].
uint8_t data[4] = {0x12, 0x34, 0x56, 0x78};
uint8_t result = get_byte(data, sizeof(data), 0);
// result = 0x12;
result = get_nibble(data, sizeof(data), 0);
// result = 0x1;
bool success = copy_bits_right_aligned(data, 4, 4, 12, result, 4)
// success == true
// result[0] == 0x2
// result[1] == 0x34If you are dealing with 8 byte CAN messages as uint64_t, there are some
additional functions prefixed with eightbyte_ that may be faster or more
useful.
uint64_t data = 0x8000000000000000;
uint64_t result = eightbyte_get_bitfield(data, 0, 1, false);
// result == 0x1
data = 0x0402574d555a0401;
result = eightbyte_get_bitfield(data, 16, 32, false);
// result = 0x574d555a;
data = 0x00000000F34DFCFF;
result = eightbyte_get_byte(data, 0, false);
//result = 0x0
result = eightbyte_get_byte(data, 4, false);
//result = 0xF3
result = eightbyte_get_nibble(data, 10, false);
//result = 0x4;uint64_t data = 0;
fail_unless(8byte_set_bitfield(1, 0, 1, &data));
uint64_t result = eightbyte_get_bitfield(data, 0, 1, false);
ck_assert_int_eq(result, 0x1);The library supports encoding floating point CAN signals as well as booleans into a uint64_t payload.
uint64_t payload = eightbyte_encode_float(1, 1, 3, 1, 0)
// payload == 0x1000000000000000
payload = eightbyte_encode_bool(true, 1, 3);
// payload == 0x1000000000000000The library supports parsing floating point CAN signals as well as booleans.
uint64_t payload = 0xeb00000000000000;
float float_result = eightbyte_parse_float(payload,
2, // starting bit
4, // width of the signal's field
1001.0, // transformation factor for the signal value
-30000.0); // transformation offset for the signal value
// float_result == -19990.0
bool bool_result = eightbyte_parse_bool(payload,
0, // starting bit
1, // width of the signal's field
1.0, // transformation factor for the signal value
0); // transformation offset for the signal value
// bool_result == trueThe library includes a test suite that uses the check C unit test library. It
requires the unit testing library check.
$ make test
You can also see the test coverage if you have lcov installed and the
BROWSER environment variable set to your choice of web browsers:
$ BROWSER=google-chrome-stable make coverage
Chris Peplin [email protected]
Copyright (c) 2013 Ford Motor Company
Licensed under the BSD license.
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