altos: ao_fec_prepare using wrong value for input len

The FEC code always sends a multiple of four bytes, padding by two
bytes for even inputs and one byte for odd. But the preparation step
was using the wrong value for the length, so the output was getting
mangled.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

src/kernel/ao_fec_tx.c

@@ -74,7 +74,7 @@ ao_fec_prepare(const uint8_t *in, uint8_t len, uint8_t *extra)
 	extra[i++] = (uint8_t) crc;
 
 	/* Append FEC -- 1 byte if odd, two bytes if even */
-	num_fec = 2 - (i & 1);
+	num_fec = 2 - (len & 1);
 	while (num_fec--)
 		extra[i++] = AO_FEC_TRELLIS_TERMINATOR;
 	return i;