diff --git a/firmware/libboard/octsimtest/source/mcp23017.c b/firmware/libboard/octsimtest/source/mcp23017.c
index bc6bd49f..959f2c6e 100644
--- a/firmware/libboard/octsimtest/source/mcp23017.c
+++ b/firmware/libboard/octsimtest/source/mcp23017.c
@@ -94,7 +94,7 @@ out_stop:
 
 int mcp23017_init(uint8_t slave, uint8_t iodira, uint8_t iodirb)
 {
-	printf("mcp23017_init\n\r");
+	TRACE_DEBUG("mcp23017_init\n\r");
 
 	// all gpio input
 	if (mcp23017_write_byte(slave, MCP23017_IODIRA, iodira))
@@ -105,11 +105,11 @@ int mcp23017_init(uint8_t slave, uint8_t iodira, uint8_t iodirb)
 	if (mcp23017_write_byte(slave, MCP23017_IOCONA, 0x20)) //disable SEQOP (autoinc addressing)
 		goto out_err;
 
-	printf("mcp23017 found\n\r");
+	TRACE_DEBUG("mcp23017 found\n\r");
 	return 0;
 
 out_err:
-	printf("mcp23017 NOT found!\n\r");
+	TRACE_WARNING("mcp23017 NOT found!\n\r");
 	return -1;
 }
 
diff --git a/firmware/libboard/octsimtest/source/mux.c b/firmware/libboard/octsimtest/source/mux.c
index 54c6cb6e..8800ba26 100644
--- a/firmware/libboard/octsimtest/source/mux.c
+++ b/firmware/libboard/octsimtest/source/mux.c
@@ -54,7 +54,7 @@ void mux_init(void)
 /* set the slot selection mux */
 int mux_set_slot(uint8_t s)
 {
-	printf("%s(%u)\r\n", __func__, s);
+	TRACE_INFO("%s(%u)\r\n", __func__, s);
 
 	if (s > 7)
 		return -EINVAL;
@@ -90,7 +90,7 @@ int mux_get_slot(void)
 /* set the frequency divider mux */
 void mux_set_freq(uint8_t s)
 {
-	printf("%s(%u)\r\n", __func__, s);
+	TRACE_INFO("%s(%u)\r\n", __func__, s);
 
 	/* no need for 'break before make' here, this would also affect
 	 * the SIM card I/O signals which we don't want to disturb */