diff --git a/artiq/runtime/analyzer.c b/artiq/runtime/analyzer.c
index 4a3ec9de2..f40188ab6 100644
--- a/artiq/runtime/analyzer.c
+++ b/artiq/runtime/analyzer.c
@@ -71,7 +71,7 @@ void analyzer_start(void)
         analyzer_header.sent_bytes = analyzer_header.total_byte_count;
 
     analyzer_header.overflow_occured = rtio_analyzer_message_encoder_overflow_read();
-    analyzer_header.log_channel = 0;
+    analyzer_header.log_channel = CONFIG_RTIO_LOG_CHANNEL;
     analyzer_header.dds_channel = CONFIG_RTIO_DDS_CHANNEL;
 #ifdef DDS_ONEHOT_SEL
     analyzer_header.dds_onehot_sel = 1;
diff --git a/artiq/runtime/ksupport.c b/artiq/runtime/ksupport.c
index 2f775cf4b..3da82f76f 100644
--- a/artiq/runtime/ksupport.c
+++ b/artiq/runtime/ksupport.c
@@ -107,6 +107,7 @@ static const struct symbol runtime_exports[] = {
 
     /* direct syscalls */
     {"rtio_get_counter", &rtio_get_counter},
+    {"rtio_log", &rtio_log},
 
     {"ttl_set_o", &ttl_set_o},
     {"ttl_set_oe", &ttl_set_oe},
@@ -167,13 +168,15 @@ int fprintf(FILE *stream, const char *fmt, ...)
 }
 
 /* called by libunwind */
-int dladdr (const void *address, Dl_info *info) {
+int dladdr (const void *address, Dl_info *info)
+{
     /* we don't try to resolve names */
     return 0;
 }
 
 /* called by libunwind */
-int dl_iterate_phdr (int (*callback) (struct dl_phdr_info *, size_t, void *), void *data) {
+int dl_iterate_phdr (int (*callback)(struct dl_phdr_info *, size_t, void *), void *data)
+{
     Elf32_Ehdr *ehdr;
     struct dl_phdr_info phdr_info;
     int retval;
@@ -200,7 +203,8 @@ int dl_iterate_phdr (int (*callback) (struct dl_phdr_info *, size_t, void *), vo
     return retval;
 }
 
-static Elf32_Addr resolve_runtime_export(const char *name) {
+static Elf32_Addr resolve_runtime_export(const char *name)
+{
     const struct symbol *sym = runtime_exports;
     while(sym->name) {
         if(!strcmp(sym->name, name))
diff --git a/artiq/runtime/rtio.c b/artiq/runtime/rtio.c
index 0bf0fde5b..35c8bb309 100644
--- a/artiq/runtime/rtio.c
+++ b/artiq/runtime/rtio.c
@@ -38,3 +38,32 @@ void rtio_process_exceptional_status(int status, long long int timestamp, int ch
             timestamp, channel, 0);
     }
 }
+
+void rtio_log(long long int timestamp, char *message)
+{
+    unsigned int word;
+    int i;
+
+    rtio_chan_sel_write(CONFIG_RTIO_LOG_CHANNEL);
+    rtio_o_timestamp_write(timestamp);
+
+    i = 0;
+    word = 0;
+    while(1) {
+        word >>= 8;
+        word |= *message << 24;
+        if(*message == 0) {
+            rtio_o_data_write(word);
+            rtio_o_we_write(1);
+            break;
+        }
+        message++;
+        i++;
+        if(i == 4) {
+            rtio_o_data_write(word);
+            rtio_o_we_write(1);
+            word = 0;
+            i = 0;
+        }
+    }
+}
diff --git a/artiq/runtime/rtio.h b/artiq/runtime/rtio.h
index 702c381c4..d8273f3f2 100644
--- a/artiq/runtime/rtio.h
+++ b/artiq/runtime/rtio.h
@@ -14,6 +14,7 @@
 void rtio_init(void);
 long long int rtio_get_counter(void);
 void rtio_process_exceptional_status(int status, long long int timestamp, int channel);
+void rtio_log(long long int timestamp, char *message);
 
 static inline void rtio_write_and_process_status(long long int timestamp, int channel)
 {