Refactor parallel comms a bit

paracomm.h

@@ -2,18 +2,24 @@
 
 #include <stdint.h>
 
-typedef void (*miso_cb_t)(const uint8_t* buff, uint8_t size);
-
 /** Must call first **/
-void paracomm_init(miso_cb_t miso_cb);
+void paracomm_init();
 
 /** Sends a single byte.
  * Returns: 0 if no error, non-0 otherwise.
  */
 int paracomm_send(uint8_t b);
 
+/** Receive some bytes.
+ * Returns: number of bytes copied
+ */
+uint8_t paracomm_recv(uint8_t* buf, uint8_t size);
+
 /** Call after reading a nibble from the port */
 void paracomm_feed(uint8_t n);
 
 /** Yields the next byte to send out the port */
 uint8_t paracomm_nextbyte();
+
+/** Returns non-zero if busy */
+uint8_t paracomm_busy();