{"id":354,"date":"2021-07-08T10:42:12","date_gmt":"2021-07-08T09:42:12","guid":{"rendered":"https:\/\/avionicsduino.com\/?page_id=354"},"modified":"2025-07-06T15:52:20","modified_gmt":"2025-07-06T14:52:20","slug":"efis-2","status":"publish","type":"page","link":"https:\/\/avionicsduino.com\/index.php\/en\/efis-2\/","title":{"rendered":"EFIS"},"content":{"rendered":"\n

(EFIS: Last updated by Benjamin on March 25, 2024)<\/em><\/p>\n\n\n\n

The EFIS or Electronic Flight Instrument System combines the indications of the primary flight instruments, at least the artificial horizon, the ball, the turn indicator, the anemometer, the altimeter, the variometer, and the compass, on a single display. Before the widespread use of EFIS and digital technology on aircraft instrument panels, an individual device was dedicated to each function, generally based on analog, electromechanical, or pneumatic technology.<\/p>\n\n\n\n

As an EFIS is first and foremost a computer, the list of other indications or functions that can be implemented is not exhaustive: density altitude, true air speed, angle of attack, outside temperature, G-meter, wind speed and direction, voltmeter, clock, autopilot\u2026 etc.<\/p>\n\n\n\n

This page will describe the main unit of the AvionicsDuino EFIS. The reader can refer to the AHRS <\/a>and Digital Compass<\/a> pages for the description of these modules, which are integral parts of the EFIS.<\/p>\n\n\n\n

AvionicsDuino EFIS general presentation<\/h3>\n\n\n\n

The primary function of the main EFIS unit is to manage the screen (graphical display of the artificial horizon and all textual data) and make many complex calculations to convert raw sensor data into human-readable format useful information for pilots.<\/p>\n\n\n\n

For example, compute the aircraft’s speed from static and total pressure measurements. Or calculate the position of the ball based on lateral accelerations. This unit itself contains a very limited number of sensors, namely the two pressure sensors (absolute for static pressure and differential for the Pitot probe) and the inside air temperature sensor.<\/p>\n\n\n\n

All other sensors are located in the above-mentioned modules (AHRS and Digital Compass): GNSS, gyrometers, accelerometers, magnetometers, outside air temperature, and relative humidity sensors. Complex computations are also performed in these modules.<\/p>\n\n\n\n

EFIS general architecture<\/h3>\n\n\n\n

It is shown schematically in Figure 1. The main unit is represented in the yellow box, the AHRS in the pink one, and the magnetometer module, with outside air temperature and relative humidity sensors in the green one.<\/p>\n\n\n

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Figure 1: AvionicsDuino EFIS general architecture<\/figcaption><\/figure>\n<\/div>\n\n\n

The main unit includes a 5-volt power supply (described elsewhere<\/a>). This power supply also provides the voltage required by the other two modules (red arrows). It uses one of the two twisted pairs within the CAN Bus Cable.<\/p>\n\n\n\n

All modules communicate with each other via the CAN bus<\/a> (green arrows). In earlier software versions, the AHRS communicated with the EFIS main unit via a serial UART channel, shown in Figure 1 by a two-way dotted blue arrow. This UART serial communication has become obsolete, but the software versions that used it can still be downloaded from GitHub. However, they will no longer evolve and will no longer be updated.<\/p>\n\n\n\n

Main components<\/h3>\n\n\n\n

The heart of the main unit is a PJRC Teensy 4.1 board equipped with an NXP i.MXRT1062 microcontroller (ARM Cortex-M7 @ 600 MHz). See the microcontroller boards page<\/a>.<\/p>\n\n\n\n

The other components are listed below:<\/p>\n\n\n\n