M17 Project CC1200 – Amateur Radio Update

DMR users have long used an operating system called Pi-Star and WPSD to act as a gateway to their systems. Pi-Star and WPSD both included M17 support. I found that it was easiest and worked best under Pi-Star. The maintainer of both programs has removed M17 from their software. Currently my WPSD has the M17 removed since the last software update. I still have it on Pi-Star but I imagine it will go away with the next update.

Sadly, this is probably going to make a hit against the usability for M17 users. There are several other ways to connect to M17 and I’ll explore one of those today.

NOTE: I am not a super experienced M17 user as I just started using the protocol a a few months ago. As I set up a new device to connect to M17 yesterday (CC1200 hotspot board) the M17 folks had to hold my hand and work me through getting connected. It’s not hard at all but it isn’t intuitive. Especially, setting up the radio.

CC1200 Hotspot

One such way to connect is via a CC1200 hotspot. I read about one somewhere and decided to give it a try. Sadly I could not find a board to buy. That being said a manufacturer in China called PCBWay will manufacture them for you. I had 5 manufactured and will probably sell the other 4 of them.

Note that they will come without an antenna and I opted to not have the pin headers installed. When I DIY something like this I like to have my hand in at least some soldering or something.

I can confirm that the boards work as advertised. I placed mine on top of a Pi 3B+ I had laying around but I will probably rebuild this on a Pi 4 soon. I’m not sure if this will work on a Pi 5 but it probably will.

Readying The Pi And The CC1200 Board Firmware

This is done on top of PiOS so you simply prepare an SD card as you would any other Pi. I used 32 bit Bookworm. Right after that I will link to the page of directions. I can’t write them any better than this. The directions are located here.

There are several methods for flashing the firmware to the board as well. They are explained in great detail. I used the USB method before installing the board on the Raspberry Pi.

Once you get the dependencies installed, and the configuration file set up you can launch the program with the following command. Be sure to invoke it from inside the rpi-interface directory.

sudo rpi-interface -c my_cfg.txt

That gets you to this:

The file my_cfg.txt looks like this for my hotspot. Note the items in bold are what I changed:

  GNU nano 7.2                                                                                     my_cfg.txt                                                                                               
#Main settings
log_path="/home/pi/m17.txt"            " #log file for the dashboard
device="/dev/ttyAMA0"                   #UART port to use
speed=460800                            #UART's speed
node="KN4FMV H"                         #callsign with a suffix
ipv4="152.70.192.70"                    #reflector's IPv4 address
port=17000                              #reflector's port
reflector="M17-M17"                     #reflector name
module="C"                              #module, single letter
nrst=21                                 #nRST pin
pa_en=18                                #PA enable pin (unused by the CC1200 HAT)
boot0=20                                #BOOT0 pin

#RF settings
tx_freq=433475000                       #Hz
rx_freq=433475000                       #Hz
freq_corr=14                             #frequency correction (integer)
tx_pwr=14.0                             #transmission power, dBm
afc=1                                   #automatic frequency control (0-off, 1-on)
zmq_port=17017                         #ZMQ PUB port for the baseband signal

The hardest part is finding your frequency correction. Just play with the numbers until you achieve routine success. My offset was 14. Your mileage may vary. Oddly enough when I first start the hotspot the correction starts around 60 and stabilizes after a bit to where 14 seems to be the sweet spot. It is a little bit drifty. Most probably a heat thing.

And, whenever you want to change reflectors you have to do it in the my_cfg.txt file AND on the radio. I use a Connect Systems CS7000.

I built this on top of a Pi 3 at first and the SD card I think was rotten. I re-flashed my OS on a new card and dropped it on top of a Pi 2 Zero W. So far so good.

Your First M17 Project CC1200 Transmission

Once you calculate your frequency correction, you are off to the races.

So this is considerably different than Pi-Star or WPSD both of which are dropping support for M17.

Setting Up The Radio

Here is a video showing how to set up the CS7000 radio for the CC1200 hotspot. Every bit of this was the M17 Project guys holding my hand. I DID NOT know how to set up the radio. Thanks to the M17 Project for providing timely and great help to me.

I may have glossed over this a bit but now you have more info than I did going into this M17 Project.

Again, Kudos to the M17 bubbas for providing great documentation and for helping me with the radio setup. I could not have done it without their help.

Hey, and email me if you want to buy a CC1200 board.