Add check that device is ready for the number of bytes we will send i…

…n binary mode.

At the moment, if it fails it will simply send all zeros and throw an error.
I think this is the best option, as it prevents the device from getting locked up waiting for bytes (if we restart the blacs tab).

labscript_devices/AD9959DDSSweeper/blacs_workers.py

@@ -139,6 +139,11 @@ def set_batch(self, table):
         if not resp.startswith('ready'):
             resp += ''.join([r.decode() for r in self.conn.readlines()])
             raise LabscriptError(f'setb command failed, got response {repr(resp)}')
+        ready_for_bytes = int(resp[len('ready for '):-len(' bytes\n')])
+        if ready_for_bytes != len(table.tobytes()):
+            self.conn.write(b'\0'*ready_for_bytes)
+            self.assert_OK()
+            raise LabscriptError(f'Device expected {ready_for_bytes}, but we only had {len(table.tobytes())}. Device mode likely incorrect.'
         self.conn.write(table.tobytes())
         self.assert_OK()