extract big-endian signals from frames

1 files changed, 33 insertions, 0 deletions

diff --git a/fw/signal.h b/fw/signal.h
new file mode 100644
index 0000000..8bbc120
--- /dev/null
+++ b/fw/signal.h
@@ -0,0 +1,33 @@
+/** DBC Signals.
+ * See "DBC File Format Documentation" v.01/2007
+ *
+ * Device PIC16F1459
+ * Compiler: XC8 v3.00
+ *
+ * Usage:
+ *
+ * #include <stdbool.h>
+ * #include <stdint.h>
+ * #include "types.h"
+ * #include "can.h"
+ * #include "signal.h"
+ */
+
+// Byte order
+typedef enum {
+	LITTLE_ENDIAN = 0,
+	BIG_ENDIAN,
+} ByteOrder;
+
+// A Signal Format defines how a DBC signal is encoded in a CAN frame.
+typedef struct {
+	CanId id; // ID of message containing the signal
+	U8 start; // start bit -- position of signal within DATA FIELD
+	U8 size; // size of the signal in bits
+	ByteOrder order; // little-endian/big-endian
+	bool isSigned;
+} SigFmt;
+
+// Extract the raw signal value out of a CAN frame's DATA FIELD.
+// Assumes the frame's ID matches that of the signal.
+Status sigPluck(const SigFmt *sig, const CanFrame *frame, Number *raw);