Tutorial: Connecting to the autopilot

[Evan Schellenberg]

If you are having any issues connecting to your autopilot in Horizon, please read the below instructions on connecting with a direct (wired) serial connection.

We have found that USB to Serial adapter cables with an FTDI chipset in them are the most reliable so make sure the one you are using has one. Without an FTDI chip in the cable a common problem is being able to connect to TeraTerm but not to Horizon, or intermittently being able to connect to Horizon.

So if you are using an adapter without an FTDI chipset that is most likely the cause of connectivity problems.

 

Make sure that your computer recognizes the adapter properly by plugging it into the computer with nothing attached to the serial end. If a device is attached to the other end it may cause Windows to recognize the adapter as a different type of USB device. Once Windows is done installing drivers for the adapter you should see a new COM port in Device Manager (accessed via Windows control panel). This is the COM port you need to use when connecting in Horizon.

 

If the autopilot is attached to the USB to Serial Adapter when the computer is turned on, Windows may recognize the autopilot as a mouse. This will cause the mouse on your screen to jump around by itself. Unplug the USB adapter or unplug the autopilot from the serial end of the USB adapter and restart your computer to fix this.

 

When connecting directly to the autopilot through a terminal program we recommend TeraTerm. Hyperterminal, as recommended in our manuals, is not included with Windows installations newer than Windows XP so an alternative is needed. TeraTerm (http://en.sourceforge.jp/projects/ttssh2/releases/) is a free program that will allow you to connect directly to your autopilot. Another alternative is Putty (http://www.putty.org/).

 

To connect in TeraTerm, connect your autopilot to your USB to Serial Adapter. Then click "File" -> "New Connection". A box will pop up. Select the "Serial" option and then choose the appropriate COM port from the drop down list and then click "OK".

TeraTerm should now be connected to the autopilot, you may see output that appears to be gibberish, this means that either the baud rate in TeraTerm doesn't match the autopilot's baud rate, or the autopilot is in GCS mode.

If you see English characters that show the startup report then you are already using the correct baud rate.

 

If you do not see readable output then the next step is to select the proper baud rate. Click "Setup" -> "Serial Port.." to open the serial port settings. The COM port you are connected to should be selected automatically. Try changing the baud rate to the different settings between 9600 and 57600 and then click "OK". One of these settings should give you readable output. When connecting in TeraTerm, CRC, parity, and other settings are (mostly) ignored, so changing only the baud rate should be all you need to do.

 

If you have tried all of the baud rate settings and there is still gibberish for output that may indicate that the autopilot is already in GCS mode. Connecting or attempting to connect to Horizon will switch the autopilot to GCS mode and it will begin sending telemetry, this will appear unreadable in TeraTerm as it is data meant for Horizon. Cycling power to the autopilot will fix this and it won't switch to GCS mode until you attempt to connect to Horizon.

 

Once you have found the baud rate the autopilot is using you can now send commands to the autopilot. More info on these are found in the autopilot manual. Below is more info on checking other comm settings on the autopilot through TeraTerm.

 

Horizon does not ignore the other comm settings, so you will need to find out what these are set to before being able to connect to Horizon.

 

Try pressing QQQQ to enter setup mode.

If that command works TeraTerm will show something like:

"Parameters

MP2128Heli2:"

 

If it shows that after pressing "QQQQ" then you have entered setup mode. If sending commands does not work (nothing happens after pressing QQQQ), one cause for this is the Parity setting. Try setting this to Odd or Even and see if you are able to send the command.

 

 

After you have entered setup mode press "X" to examine a field and then press "581" for the gcsCRCenable field. Then press Enter and it should show the value of field 581 on the autopilot.

 

If this is 1 it means that CRC is enabled and if it is 0 then CRC is disabled.

 

When connecting with Horizon, make the Horizon settings for UAVX (Where X is the UAV number you are using) have the "Enable CRC (32bit)" checkbox (On the Comms tab of Horizon settings) selected or unselected, depending on whether or not it is enabled based on the value of field 581. Make sure the Horizon Settings for the other fields below are set (in the Comms tab) to match the value on the autopilot.

 

So make sure the baud rate and "Enable CRC" option in Horizon Settings are set to match what is on the autopilot.

If you still can't connect to Horizon, examine autopilot fields 193,580 and 540 in TeraTerm and make sure the Horizon Comm settings match the settings on the autopilot. The manual describes what these fields are on page 239.

 

Once the Horizon Comm settings match the autopilot's you will be able to connect in Horizon.

 

Always cycle the power to the autopilot when you are done using Setup mode or the autopilot will be unable to connect to Horizon since it will still be in Setup mode.

 

Make sure to check the Comm fields on any VRS you transmit to make sure they are set to the desired Comm settings or else the autopilot will switch to use the new settings in the VRS file.