diff --git a/Inc/AdcIO.h b/Inc/AdcIO.h
index 3ee083d..4be0d73 100644
--- a/Inc/AdcIO.h
+++ b/Inc/AdcIO.h
@@ -7,10 +7,12 @@
 
 #include "stdint.h"
 
-typedef float (*AdcIOTransaction  )(void *env, uint32_t timeout);
+typedef void (*AdcIOStartTransaction )(void *env);
+typedef uint8_t (*AdcIOTransaction  )(void *env, uint32_t *buf, uint32_t timeout);
 
 typedef struct {
     void *env;
+    AdcIOStartTransaction start;
     AdcIOTransaction get;
 } tAdcIO;