K

only:mre_f4

firmware/util/math/crc8hondak.cpp

@@ -0,0 +1,41 @@
+#include <stddef.h>
+#include <stdint.h>
+
+#include "crc8hondak.h"
+
+static inline uint8_t crc_init(void)
+{
+	return 0xff;
+}
+
+static inline uint8_t crc_next(uint8_t crc, uint8_t data)
+{
+	uint8_t eor;
+	unsigned int i = 8;
+
+	crc ^= data;
+	do {
+		/* This might produce branchless code */
+		eor = crc & 1 ? 0xb8 : 0;
+		crc >>= 1;
+		crc ^= eor;
+	} while (--i);
+
+	return crc;
+}
+
+static inline uint8_t crc_final(uint8_t crc)
+{
+	return ~crc;
+}
+
+uint8_t crc_hondak_calc(const uint8_t *data, size_t len)
+{
+	uint8_t crc = crc_init();
+
+	if (len) do {
+		crc = crc_next(crc, *data++);
+	} while (--len);
+
+	return crc_final(crc);
+}

firmware/util/math/crc8hondak.h

@@ -0,0 +1,19 @@
+/*
+ * crc8hondak.h
+ *
+ * Code generated by universal_crc by Danjel McGougan
+ *
+ * matches CRC8_EBU with 0xFF OutXor
+ *
+ * CRC parameters used:
+ *   bits:       8
+ *   poly:       0x1d
+ *   init:       0xff
+ *   xor:        0xff
+ *   reverse:    true
+ *   non-direct: false
+ *
+ * CRC of the string "123456789" is 0x68
+ */
+
+uint8_t crc_hondak_calc(const uint8_t *data, size_t len);

firmware/util/util.mk

@@ -12,6 +12,7 @@ UTILSRC_CPP = \
 	$(UTIL_DIR)/math/error_accumulator.cpp \
 	$(UTIL_DIR)/math/efi_pid.cpp \
 	$(UTIL_DIR)/math/interpolation.cpp \
+	$(UTIL_DIR)/math/crc8hondak.cpp \
 	$(PROJECT_DIR)/util/datalogging.cpp \
 	$(PROJECT_DIR)/util/loggingcentral.cpp \
 	$(PROJECT_DIR)/util/cli_registry.cpp \

unit_tests/tests/util/test_honda_crc.cpp

@@ -0,0 +1,15 @@
+#include "pch.h"
+#include "crc8hondak.h"
+
+
+TEST(util, crc8hondak) {
+	const uint8_t data[] = {0x1, 0, 0};
+
+	ASSERT_EQ(140, crc_hondak_calc(data, 3));
+}
+
+// https://rusefi.com/forum/viewtopic.php?p=47283#p47283
+TEST(util, crc8hondak_2) {
+	const uint8_t data[] = {0, 0xD0, 0x06, 0};
+	ASSERT_EQ(0x62, crc_hondak_calc(data, 4));
+}

unit_tests/tests/util/test_util.mk

@@ -3,6 +3,7 @@
 CPPSRC += 	$(PROJECT_DIR)/../unit_tests/tests/util/test_buffered_writer.cpp \
 	$(PROJECT_DIR)/../unit_tests/tests/util/test_error_accumulator.cpp \
 	$(PROJECT_DIR)/../unit_tests/tests/util/test_exp_average.cpp \
+	$(PROJECT_DIR)/../unit_tests/tests/util/test_honda_crc.cpp \
 	$(PROJECT_DIR)/../unit_tests/tests/util/test_hash.cpp \
 	
 INCDIR += $(PROJECT_DIR)/controllers/system