diff --git a/src/main/bio2drv/bi2a-iidx.c b/src/main/bio2drv/bi2a-iidx.c
index 0738921..2f7a6e3 100644
--- a/src/main/bio2drv/bi2a-iidx.c
+++ b/src/main/bio2drv/bi2a-iidx.c
@@ -9,7 +9,10 @@
 
 #include "util/log.h"
 
-static const uint8_t _BIO2DR_BI2A_IIDX_INIT_DATA = 0x3B;
+// Must be provided on init command. Actual meaning unknown right now.
+// Not providing this will not initialize the IO correctly resulting
+// in all inputs and outputs (over sub IO) other than 14 keys to not work.
+static const uint8_t _BIO2DR_BI2A_IIDX_INIT_DATA = 0x2D;
 
 static bool bio2drv_bi2a_iidx_init_io(uint8_t node_id)
 {