diff --git a/Makefile.am b/Makefile.am
index b1771bc8..a0701c97 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -239,6 +239,7 @@ src_iwd_SOURCES = src/main.c linux/nl80211.h src/iwd.h src/missing.h \
 					src/frame-xchg.h src/frame-xchg.c \
 					src/eap-wsc.c src/eap-wsc.h \
 					src/wscutil.h src/wscutil.c \
+					src/diagnostic.h src/diagnostic.c \
 					$(eap_sources) \
 					$(builtin_sources)
 
diff --git a/src/diagnostic.c b/src/diagnostic.c
new file mode 100644
index 00000000..034229a7
--- /dev/null
+++ b/src/diagnostic.c
@@ -0,0 +1,109 @@
+/*
+ *
+ *  Wireless daemon for Linux
+ *
+ *  Copyright (C) 2021  Intel Corporation. All rights reserved.
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <ell/ell.h>
+
+#include "src/diagnostic.h"
+#include "src/dbus.h"
+
+/*
+ * Appends values from diagnostic_station_info into a DBus dictionary. This
+ * assumes the DBus dictionary array has already been 'entered', and expects the
+ * caller to 'leave' once called. This does not append the station address
+ * since the dictionary key name may be different depending on the caller.
+ */
+bool diagnostic_info_to_dict(const struct diagnostic_station_info *info,
+				struct l_dbus_message_builder *builder)
+{
+	int16_t rssi = (int16_t)info->cur_rssi;
+
+	if (info->have_cur_rssi)
+		dbus_append_dict_basic(builder, "RSSI", 'n', &rssi);
+
+	if (info->have_rx_mcs) {
+		switch (info->rx_mcs_type) {
+		case DIAGNOSTIC_MCS_TYPE_HT:
+			dbus_append_dict_basic(builder, "RxMode", 's',
+						"802.11n");
+			dbus_append_dict_basic(builder, "RxMCS", 'y',
+						&info->rx_mcs);
+			break;
+		case DIAGNOSTIC_MCS_TYPE_VHT:
+			dbus_append_dict_basic(builder, "RxMode", 's',
+						"802.11ac");
+			dbus_append_dict_basic(builder, "RxMCS", 'y',
+						&info->rx_mcs);
+			break;
+		case DIAGNOSTIC_MCS_TYPE_HE:
+			dbus_append_dict_basic(builder, "RxMode", 's',
+						"802.11ax");
+			dbus_append_dict_basic(builder, "RxMCS", 'y',
+						&info->rx_mcs);
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (info->have_tx_mcs) {
+		switch (info->tx_mcs_type) {
+		case DIAGNOSTIC_MCS_TYPE_HT:
+			dbus_append_dict_basic(builder, "TxMode", 's',
+						"802.11n");
+			dbus_append_dict_basic(builder, "TxMCS", 'y',
+						&info->tx_mcs);
+			break;
+		case DIAGNOSTIC_MCS_TYPE_VHT:
+			dbus_append_dict_basic(builder, "TxMode", 's',
+						"802.11ac");
+			dbus_append_dict_basic(builder, "TxMCS", 'y',
+						&info->tx_mcs);
+			break;
+		case DIAGNOSTIC_MCS_TYPE_HE:
+			dbus_append_dict_basic(builder, "TxMode", 's',
+						"802.11ax");
+			dbus_append_dict_basic(builder, "TxMCS", 'y',
+						&info->tx_mcs);
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (info->have_tx_bitrate)
+		dbus_append_dict_basic(builder, "TxBitrate", 'u',
+					&info->tx_bitrate);
+
+	if (info->have_rx_bitrate)
+		dbus_append_dict_basic(builder, "RxBitrate", 'u',
+					&info->rx_bitrate);
+
+	if (info->have_expected_throughput)
+		dbus_append_dict_basic(builder, "ExpectedThroughput", 'u',
+					&info->expected_throughput);
+
+	return true;
+}
diff --git a/src/diagnostic.h b/src/diagnostic.h
index a4fc5361..cd23bb61 100644
--- a/src/diagnostic.h
+++ b/src/diagnostic.h
@@ -47,3 +47,6 @@ struct diagnostic_station_info {
 	bool have_tx_bitrate : 1;
 	bool have_expected_throughput : 1;
 };
+
+bool diagnostic_info_to_dict(const struct diagnostic_station_info *info,
+				struct l_dbus_message_builder *builder);