diff --git a/host/include/osmocom/simtrace2/apdu_dispatch.h b/host/include/osmocom/simtrace2/apdu_dispatch.h
index af9c9897..42a097aa 100644
--- a/host/include/osmocom/simtrace2/apdu_dispatch.h
+++ b/host/include/osmocom/simtrace2/apdu_dispatch.h
@@ -1,6 +1,6 @@
 /* apdu_dispatch - State machine to determine Rx/Tx phases of APDU
  *
- * (C) 2016 by Harald Welte <hwelte@hmw-consulting.de>
+ * (C) 2016-2019 by Harald Welte <hwelte@hmw-consulting.de>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -44,6 +44,8 @@ enum osmo_apdu_action {
 	APDU_ACT_RX_MORE_CAPDU_FROM_READER	= 0x0002,
 };
 
+const char *osmo_apdu_dump_context_buf(char *buf, unsigned int buf_len,
+					const struct osmo_apdu_context *ac);
 
 int osmo_apdu_segment_in(struct osmo_apdu_context *ac, const uint8_t *apdu_buf,
 			 unsigned int apdu_len, bool new_apdu);
diff --git a/host/lib/apdu_dispatch.c b/host/lib/apdu_dispatch.c
index 835b8bc1..ec368b2d 100644
--- a/host/lib/apdu_dispatch.c
+++ b/host/lib/apdu_dispatch.c
@@ -42,7 +42,7 @@ static inline bool is_de_complete(struct osmo_apdu_context *ac)
 	return (ac->le.tot == ac->le.cur);
 }
 
-static const char *dump_apdu_hdr(const struct osim_apdu_cmd_hdr *h)
+static const char *stringify_apdu_hdr(const struct osim_apdu_cmd_hdr *h)
 {
 	static char buf[256];
 	sprintf(buf, "CLA=%02x INS=%02x P1=%02x P2=%02x P3=%02x",
@@ -51,12 +51,19 @@ static const char *dump_apdu_hdr(const struct osim_apdu_cmd_hdr *h)
 	return buf;
 }
 
-static void dump_apdu_ctx(const struct osmo_apdu_context *ac)
+/*! generate string representation of APDU context in specified output buffer.
+ *  \param[in] buf output string buffer provided by caller
+ *  \param[in] buf_len size of buf in bytes
+ *  \param[in] ac APDU context to dump in buffer
+ *  \returns pointer to buf on success */
+const char *osmo_apdu_dump_context_buf(char *buf, unsigned int buf_len,
+				       const struct osmo_apdu_context *ac)
 {
-	printf("%s; case=%d, lc=%d(%d), le=%d(%d)\n",
-		dump_apdu_hdr(&ac->hdr), ac->apdu_case,
-		ac->lc.tot, ac->lc.cur,
-		ac->le.tot, ac->le.cur);
+	snprintf(buf, buf_len, "%s; case=%d, lc=%d(%d), le=%d(%d)\n",
+		 stringify_apdu_hdr(&ac->hdr), ac->apdu_case,
+		 ac->lc.tot, ac->lc.cur,
+		 ac->le.tot, ac->le.cur);
+	return buf;
 }
 
 /*! \brief input function for APDU segmentation
@@ -168,7 +175,5 @@ int osmo_apdu_segment_in(struct osmo_apdu_context *ac, const uint8_t *apdu_buf,
 		return -1;
 	}
 
-	dump_apdu_ctx(ac);
-
 	return rc;
 }