diff --git a/Protocols_Details.md b/Protocols_Details.md
index 0c70479..83efcb8 100644
--- a/Protocols_Details.md
+++ b/Protocols_Details.md
@@ -98,6 +98,8 @@ Option is used to change the servo refresh rate. A value of 0 gives 50Hz (min),
 
 **RX_Num is used to give a number a given RX. You must use a different RX_Num per RX. A maximum of 16 AFHDS2A RXs are supported.**
 
+If telemetry is incomplete (missing RX RSSI for example), it means that you have to upgrade your RX firmware to version 1.6 or later. You can do it from an original Flysky TX or using a STLink like explained in [this tutorial](https://www.rcgroups.com/forums/showthread.php?2677694-How-to-upgrade-Flysky-Turnigy-iA6B-RX-to-firmware-1-6-with-a-ST-Link).
+
 CH1|CH2|CH3|CH4|CH5|CH6|CH7|CH8|CH9|CH10|CH11|CH12|CH13|CH14
 ---|---|---|---|---|---|---|---|---|---|---|---|---|---
 A|E|T|R|CH5|CH6|CH7|CH8|CH9|CH10|CH11|CH12|CH13|CH14