Rot Ctl Example

RotCtl and RotCtlD

This is an end-end-exmple using a Raspberry Pi 3, with Ubuntu controlling a RAK Spid Rotator.

We need to control the rotator, so we start with rotctl.

After some experimentation (and c++) I modified the Spid library to work well with my Spid Rak.

This is the command to "talk" to the rotator.... But firstly understand this

  • I am logged into the machine where the USB Controller is plugged in

The command I use is

rotctl -m 902 -r /dev/ttyUSB0 -s 1200 -Z

A few helpers

  • -m
    • The model number (rotctl -l | grep -i spid )
  • -r
    • The Device to connect to (ls /dev/tty*)
  • -s
    • The Speed (Yes 1200 baud ... we are only sending a few characters)
  • -Z
    • Timestamp the output

Moving the Antenna

So after giving the connect rotcl command (shown above), you are hopefully looking at a 

Rotator command:

prompt.

The first thing to do is to ask the rotator where is it ?

So just type

p

And I presently see

Azimuth: -40.00
Elevation: 0.00

Rotator command:

This makes sense my rotator is Az only (no El), and I am pointing to 320 degrees expressed as -40 ... (umm I feel another mod coming up).

So to move the Antenna say to +10 degrees

You just type

P 10 0

Note: Capital P and 2 values; Azimuth and Elevation

Wait a few seconds and type p

And it should read

Azimuth:  10.00
Elevation: 0.00

Rotator command:

Sick you head out of the window ... and make sure it is telling the truth.

RotctlD

The D means Daemon, in other words a network controlled process.

We can only attempt this if we have the previous step working 100%; And YOU MUST BE ON THE COMPUTER WHERE THE ROTATOR IS CONNECTED TOO (Yes I am speaking in a raised voice).

we however need 2 extra values...

  • Port
  • IP Address

Port

We should pick something that is

  • Not in Use
  • Greater than 1024
    • Ports less than 1024, require high privileges.

You may if running a tight firewall also have to add a rule to allow access.

So I will pick port 8900

IP Address

You can only listen on an IP Address that is "owned" by your machine.

So if you do the following command

 ip addr | grep inet

I see

    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
    inet 192.168.199.6/24 brd 192.168.199.255 scope global dynamic wlx1cbfce3d638d
    inet6 fe80::1ebf:ceff:fe3d:632d/64 scope link

So I have

  • 127.0.0.1
    • Loopback - nothing can connect to this
  • 1/128
    • ip6 Loopback - also not useful
  • 192.168.199.6/24 *A Class C(local) ip address, this is useful. But only machines in my LAN can see this
  • fe80::1ebf:ceff:fe3d:632d/64
    • ip6 local IP address [I think]

So you can specify the port of 192.168.19.6 - but if you are using DHCP, this will change - and you will keep having to change this value. So instead us

0.0.0.0

This is shorthand for "any ip address".

Running rotctld

Armed with the knowledge of Port and IP... we use the original rotctl command and enter

rotctld -t 8900 -T 0.0.0.0 -m 902 -r /dev/ttyUSB0 -s 1200 -Z

What are the new parameters

  • -t
    • The port number we will listen on, 8900 in this case.
  • -T
    • The IP Address we will listen on, 0.0.0.0 means - ALL

After we issue the command we should see

NOTHING... it will just sit there waiting for someone to connect.

Connecting to ROTCTLD

My rigctld is running on 192.168.19.6 I will connect from a machine with the ip address of 192.168.199.200.

But 1st (sent from 192.168.199.200 machine)

  • Can you ping the target machine
    • ping 192.168.199.6

If you can not ping this machine (assuming no firewall blocking it), then you are set to go.

The command is 

 rotctl -m 2 -r 192.168.199.6:8900

Parameters

  • -m
    • Model of Rotator - a Network rotator
  • -r
    • Address of the rotctld
    • 192.168.199.6:8900
    • ip_address:port

After giving this command you will see a familiar screen

Rotator command:

And so we issue the same command

p

And I see

Rotator command: p
Azimuth: 0.00
Elevation: -40.00

And to turn I again issue a P 10 0

When you are finished rotating the antenna - you can quit using q.

Please note this only disconnects the rotcl (on machine 192.168.199.200) and the Daemon is still there - listening for a new command instruction.

Remote access

This is more difficult - as you need to ensure that you can port forward from your IP/ISP connection point into your network.

Look for Port-Forwarding options on the router.

Auto Starting on Ubuntu/Linux

We have everything configured, and now we would like to start this process as soon as the machine/network starts.

sudo bash 
cd /etc/systemd/system
vi 92-rotctld.service

The file looks like this

[Unit]
Description=Rotctl Spid Service

[Service]
ExecStart=/usr/local/bin/spid_remote.sh

[Install]
WantedBy=multi-user.target

We now need to enable this service

 systemctl enable 92-rotctld.service

Now create the start_script /usr/local/bin/spid_remote.sh

The file looks like this

#!/usr/bin/bash
export LD_LIBRARY_PATH="/usr/local/lib;$LD_LIBRARY_PATH"
logger Starting rotctl for Spid
/usr/local/bin/rotctld -t 8900 -T 0.0.0.0 -m 902 -r /dev/ttyUSB0 -s 1200 -Z

Set to Execute

chmod +x /usr/local/bin/spid_remote.sh

Try and start the service

systemctl start 92-rotctl.service

Check by 

systemctl status 92-rotctl.service

I see

  Loaded: loaded (/etc/systemd/system/92-rotctld.service; enabled; vendor preset: enabled)
     Active: active (running) since Sat 2021-06-12 01:08:00 UTC; 1min 47s ago
   Main PID: 2850 (spid_remote.sh)
      Tasks: 2 (limit: 1815)
     Memory: 2.6M
     CGroup: /system.slice/92-rotctld.service
             ├─2850 /usr/bin/bash /usr/local/bin/spid_remote.sh
             └─2852 /usr/local/bin/rotctld -t 8900 -T 0.0.0.0 -m 902 -r /dev/ttyUSB0 -s 1200 -Z

Jun 12 01:08:00 ubuntu systemd[1]: Started Rotctl Spid Service.
Jun 12 01:08:00 ubuntu root[2851]: Starting rotctl for Spid

All is working...