Gray Coded Devices

(10, 12, 14, 16 bit systems)

The device described on this page was a result of some work with Christer SM4FXR who has a 16 bit Gray coded device.

The COA1E8C16 encoder (16 bit)

The secret to making this work with my system is threefold:

1. An interface to convert parallel input to serial output (this uses two 74HC165 chips)
2. New hex file for the AZ/EL interface board to enable it to poll the 74HC165 and convert the received serial gray code into a variable holding a count from 0 to 65535 and then send this in serial form to the 'Shack Unit'.
3. A modified version of the hex code for the 18F4620 so that it can deal the improved accuracy. This is Version 6.00 of the shack unit code and currently the latest version.

The interface:

Download this jpg of the circuit for the two 74HC165. Each chip converts 8 bits of the input from the encoder, the lowest significant bits from the first chip are couple to the serial input of the second chip to shuffle all 16 bits through to the AZ/EL unit.

The pin connections on the AZ/EL unit are:

The device and same software will work with any gray coded device from 10, 12, 14, 16 bit. If you have a lower definition encoder all you need do is to connect the outputs available leaving the unused most significant bits of the 74HC165 tied to earth. Adjust the menu item in the shack unit to match your definition device.

Download the hex code here for the 16F628 in the AZ/EL unit.

Here are the two files (one) and (two) of the specifications of the COA1E8C16 unit used by Christer. The manufacturer of the encoder is Codechamp S.A. in France.

Christer SM4FXR with the encoder and antenna units

Front view of 74HC165 board built on matrix (top) attached to the AZ/EL unit

Test setup on bench at SM4FXR

Christer's shack unit

SM4FXR antenna system. A 3M dish for 1296MHz EME is being planned.

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