diff --git a/simulator/data_recorder.c b/simulator/data_recorder.c
index 44109cd..7880675 100644
--- a/simulator/data_recorder.c
+++ b/simulator/data_recorder.c
@@ -79,6 +79,20 @@ void record_pin(int pin, int32_t state, uint64_t t) {
   values[pin] = state;
 }
 
+static char cmt[300];
+static char *pcmt=cmt;
+void record_comment_stream(char ch) {
+  if (ch == '\r' || ch == '\n') {
+    record_comment(cmt);
+    pcmt = cmt;
+    *pcmt = 0;
+  }
+  else if (ch && pcmt < cmt+sizeof(cmt)-1) {
+    *pcmt++ = ch;
+    *pcmt = 0;
+  }
+}
+
 void record_comment(const char * msg) {
   if (!file) return;
   fprintf(file, "# %s\n", msg);
diff --git a/simulator/serial_sim.c b/simulator/serial_sim.c
index d9331ef..29e8948 100644
--- a/simulator/serial_sim.c
+++ b/simulator/serial_sim.c
@@ -60,7 +60,6 @@ static void open_tty(const char *devname)
   sim_assert(serial_fd != -1, "couldn't open serial port");
   sim_assert(isatty(serial_fd), "not a TTY");
 
-  sim_info("configuring port");
   // Get the current options for the port
   if (tcgetattr(serial_fd, &options) != 0) {
     sim_error("tcgetattr");
@@ -125,7 +124,7 @@ uint8_t serial_popchar(void) {
 // send one character
 void serial_writechar(uint8_t data) {
   sim_assert(serial_initialised, "serial interface not initialised");
-  sim_gcode_ch(data);
+  record_comment_stream((char)data);
   if (serial_fd) {
     ssize_t count;
     count = write(serial_fd, &data, 1);
@@ -137,7 +136,7 @@ void serial_writechar(uint8_t data) {
 void serial_writestr(uint8_t *data) {
   const char *str = (char *)data;
   sim_assert(serial_initialised, "serial interface not initialised");
-  sim_gcode(str);
+  record_comment(str);
   if (serial_fd) {
     ssize_t count;
     count = write(serial_fd, str, strlen(str));