diff --git a/main/protocol.c b/main/protocol.c
index 08a9c47..c81d8b1 100644
--- a/main/protocol.c
+++ b/main/protocol.c
@@ -144,6 +144,14 @@ static int send_sysex(const uint8_t *sysex, uint16_t len)
     return wifi_send_sysex(sysex, len);
 }
 
+/* ---- outbound: keepalive ---- */
+
+int send_keepalive(void)
+{
+    uint8_t sx[] = { 0xF0, 0x7D, RSP_KEEPALIVE, 0xF7 };
+    return send_sysex(sx, sizeof(sx));
+}
+
 /* ---- outbound: EIS ---- */
 
 int send_sweep_start(uint32_t num_points, float freq_start, float freq_stop)
diff --git a/main/protocol.h b/main/protocol.h
index 54b756b..dfab429 100644
--- a/main/protocol.h
+++ b/main/protocol.h
@@ -56,6 +56,7 @@
 #define RSP_REF_LP_RANGE 0x21
 #define RSP_REFS_DONE   0x22
 #define RSP_REF_STATUS  0x23
+#define RSP_KEEPALIVE   0x50
 
 /* Session sync responses (0x4x) */
 #define RSP_SESSION_CREATED  0x40
@@ -138,6 +139,9 @@ int send_ref_lp_range(uint8_t mode, uint8_t low_idx, uint8_t high_idx);
 int send_refs_done(void);
 int send_ref_status(uint8_t has_refs);
 
+/* keepalive (sent during long blocking ops) */
+int send_keepalive(void);
+
 /* session management */
 const Session *session_get_all(uint8_t *count);
 uint8_t session_get_current(void);