Message

message/message.c

@@ -0,0 +1,52 @@
+#include "message.h"
+#include <assert.h>
+
+uint16_t compute_crc16(const uint8_t *data, uint16_t len);
+bool     is_type_valid(MessageType t);
+
+/**
+ * @brief Create a message
+ *
+ *      Use as: create_message(&m1, UI_VOLTAGE, (MessageData){.voltage = 6.3});
+ *
+ * @param m A pointer to the message struct
+ * @param type The enum type of the message you want to send
+ * @param data The data corresponding to the message type
+ */
+void message_create(Message *m, MessageType type, MessageData data) {
+    m->type = type;
+    m->data = data;
+    m->crc = compute_crc16((const uint8_t *)m, offsetof(Message, crc));
+}
+
+bool message_validate(const Message *m) {
+    return is_type_valid(m->type) && m->crc == compute_crc16((const uint8_t *)m, offsetof(Message, crc));
+}
+
+// Standard CRC-16-CCITT (poly 0x1021, init 0xFFFF)
+uint16_t compute_crc16(const uint8_t *data, uint16_t len) {
+    uint16_t crc = 0xFFFF;
+    for (uint16_t i = 0; i < len; i++) {
+        crc ^= (uint16_t)data[i] << 8;
+        for (int j = 0; j < 8; j++) {
+            if (crc & 0x8000)
+                crc = (crc << 1) ^ 0x1021;
+            else
+                crc <<= 1;
+        }
+    }
+    return crc;
+}
+
+bool is_type_valid(MessageType t) {
+    return t >= UI_SPEED_MS && t <= UI_VOLTAGE;
+}
+
+int message_tests(void) {
+    Message m;
+    message_create(&m, UI_BATTERY, (MessageData){75});
+
+    assert(message_validate(&m));
+
+    return 0;
+}