Comparison of protocols JETI Duplex and Duplex EX

Introduction

The aim of this article is to compare original JETI telemetry protocol with its newer protocol JETI Duplex EX. Duplex EX is far from being new, but nevertheless I have not seen a comparison of those two. Tha articel will focus on the practical part, without getting into too much details (those can be found at JETI model homepage.

Protocol JETI Duplex

Original JETI Duplex protocol is now more than 7 years old. The main aim was to allow displaying value(s) from a single sensor on the JETIBOX - two row LCD terminal. The architecture of the whole solution is adequate to the simple display. The display screen is generated directly in the sensor (and Tx, Rx or Expanderu) and is thereafter transferred all the way to the JETIBOX. Limitation of this approach is that even though seensors in the plane measure multiple sensor values, it is always only one JETIBOX screen that transmitted to the ground and available to the pilot. A single jetibox screen contains only limited amount of sensor values, typically 1-3. Values that are not on the JETIBOX screen were never transferred from the plane and thus are not available to the pilot.

One can imagine it as a railway system with switches (the switches are controlled from JETIBOX buttons). At any given moment, it is only one path that is connected from sensor to JETIBOX. In the picture below, the path from MVario to JETIBOX is highlighted.

When using only JETIBOX, this limitation is not obvious, as it is anyways only the one screen that the pilot can observe. Users are to this and it is not confusing at all. However, some of you are asking how is it possible that even newer and much more powerful device as RCDroidBox can't show all the values at once. The answer to this question lies in the "railway switch system". That stays unchanged even with RCDroidBox. When unsing the original duplex protocol, it is not possible to transfer more values than what is available on one screen.

Protokol JETI Duplex EX

Protocol Duplex EX does not anymore transfer data as screens with text, but as a compressed stream of binary data. All sensor values from airplane are sequentially transmitted to the ground, regardless of the screen you are just observing with JETIBOX. This approach enables processing of all the sensor data together.

Even though all data are transferred together, the speed of the transfer is limited by the RX->TX downlink. The consequence is that the more sensors you have in a plane, the less frequent the update of individual sensors will be. In our experience, GPS is the one most demanding for bandwidth.

So far, the Duplex EX protocol functions concurrently with the non-EX protocol. This means, that the data transferred from plane to the ground are suitable for JETIBOX(text screen) and for moer advanced systems as RCDroidBox, JETIBOX Profi, DC and DS transmitters.

Duplex EX, Duplex and RCDroidBox

Differences in the two protocols influence the RCDroidBox functionality. Using the old protocol, RCDRoidBox is also limited to the values that are shown on the JETIBOX screen. The straightforward rule is that RCDroidBox has access only to those values that can be shown on one JETIBOX screen (When using JETI expander, this can be data from more than one sensor).

Is it worth to use RCDroidBox with the older protocol?

RCDroidBox offers several advantages over the JETIBOX even without the use of EX protocol. When using limited number of sensors, this can be sufficient.

• Sensor value logging.
• Real time graph.
• Customa larm settings, including voice output.
• Increased readability bu using smartphone/tablet display.
• Simple access to measured values.

When is it worth to upgrade to Duplex EX?

Upgrade to EX will enable easier work with telemetry data. It is worth when you are more serious with telemetry and you want to collect, compare and analyze values from multiple sensors.
Using EX protocol is always better that using non-EX. Check the paragraph below to see if it is simple to upgrade your equipment to EX just by simple firmware upgrade.

How to determine if my device can be upgarded to Duplex EX?

• Sensors Press down arrow on JETIBOX, then several times to the right. If you reach item Servis, it is possible to upgrade to the Duplex EX.

• TX modules Connect RCDroidBox or JETIBOX tot he module and use right arrow to go through the menu. If you find screen with text FW followed by numbers, the it is possible to upgrade to Duplex EX.

• RX Procedure is the same as with TX modules, but it is not even necessary to do it. Any receiver works well with the EX data.