Bitfield Utilities in C =========================== 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: ## Bitfield Manipulation The bitfields are stored in `unsigned int[]`. unsigned int data[4] = {0x12, 0x34, 0x56, 0x78}; unsigned int 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] == 0x34 ## 8 Byte Helpers If 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. ### 8 Byte Decoding 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; ### 8 Byte Encoding 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); ### CAN Signal Encoding 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 == 0x1000000000000000 ### CAN Signal Decoding The 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 == true ## Testing The 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 ## Authors Chris Peplin cpeplin@ford.com ## License Copyright (c) 2013 Ford Motor Company Licensed under the BSD license.