An ‘ETS25 SPI’ converter to serial (MAB25)

The sensor ETS25 SPI from the company Megatron is an absolute 14 bit Hall effect rotary encoder. Absolute rotary encoders are often used for reading antenna position. The SPI version of such an encoder is relatively easy to connect to systems if the interface software is available within that system. In practice, many antenna track or position reading systems do not have this software, but software for connecting e.g. HH-12 or MAB25 devices.

Described below is a converter to connect an ETS25 SPI to an OE5JFL or HB9DRI antenna track system. The converter consists of a 5 volt Arduino board with software. A 5 volt Arduino board was chosen to avoid level converters. The 14 bits of the ETS25 SPI are converted to 14 bits of the HH12/MAB25 protocol. The trackers only use 12 of these bits.

Overview

The position information of the ETS25 SPI is read by the Arduino. This position information is sent to the antenna tracker via a serial protocol (MAB25). Optionally, a display can be connected to the Arduino on which the position information is displayed. In addition, the position information is sent to a computer via the serial monitor.

Connection diagram

The software has been tested with the Arduino UNO, NANO and MINI (5 volt version!).

In practise

The interface is built on a small piece of circuit board. If you want to keep it even smaller, solder the wires directly to the CPU board.

The software can be downloaded here. (Note: the software uses the Arduino library: LiquidCrystal I2C of Frank de Brabander)

For testing purposes, Walter, ON4BCB, loaned me an OE5JFL tracker and Sasho, LZ4OC, tested the interface with the HB9DRI tracker. Tnx both of you.