Radio Shortcut Keypad For The Yaesu FT891

Posted on February 4, 2021

The Problem

I have a Yeasu FT-891 HF radio, which I love for its small size and, relative to its size and price, great performance. However, there are a few things I came to dislike, and those mainly have to do with the lack of specialized buttons for certain functions that I found to need more often than others. Of course, in a radio of this size there are compromises to be made.

The Solution

CAT control to the rescue!

All the functions of the radio are available through menus, and most if not all can luckily also be accessed using the Computer Aided Transceiver (CAT) interface of the radio. This can nicely be controlled using a regular computer, or let’s say a Raspberry Pi. However, I wanted a smaller and standalone solution that does not need my PC to be close by. Since I just made a keypad for my computer, I thought I would make another one that simply connects to the serial interface to the radio and uses the CAT control commands to set the things I want. The CAT interface is traditionally done using a simple serial interface, but in more modern radios that is implemented using a USB interface, using a USB-to-serial bridge. This is where the fun comes in; making the custom firmware for the used STM32 chip work with the CP210 bridge in this particular radio was a little fiddly. It did however work out and this is what it looks like in real life:

At the present time, this is what it can do with one button press each:

I measured the power consumption including the little display at between 70mA and 100mA at 3.3V. That is definitely not nothing, but really not too bad. I should be able to run this for a long time even on the 2 AA batteries that I use for now. A voltage regulator is included on the board that should technically allow input voltages over 12V, so that I could also connect it to the radio’s power supply.