If you'd like to connect to APM 2.5 wirelessly but don't need the long-distance reach of the 3DR radios, you can use the Bluetooth connection built in to your laptop, along with a Bluetooth module.
Here's what you'll need to do this:
Once you get the Bluetooth module, you need to set it to the right baud rate. A guide to all the commands it can use is here, but here's the short form:
- If you have a USB Xbee adapter or an FTDI cable, use that to connect the Bluetooth adapter directly to your PC. If you don't have those, you can also do with wirelessly over Bluetooth using the Serial-over-Bluetooth process described below, but I haven't tried that myself.
- With any terminal program (TeraTerm, HyperTerm, etc), select the COM port assigned to the cable/adapter the Bluetooth module is plugged into, and set the baud rate to 115k.
- Within 60 seconds of powering on the Bluetooth module, enter "$$$". This should produce a "CMD" command prompt.
- Type "SU,57"[Return]. This will set the baud rate to 57k. It will not take effect until you power cycle the module.
- Now you can unplug it from the USB Xbee adapter or FTDI cable. Plug it into the Xbee adapter board, and with the APM adapter cable, plug it into the APM telem port.
- Power APM with the Power Module. (Don't power it via USB, since you can't use wireless and USB at the same time)
- On your PC, go into the Windows Control Panel/Hardware and Sound/Devices and Printers. Select "Add a Bluetooth device". It should see the Bluetooth module, which will be called "FireFly". Connect to it. Say OK to any boxes that come up about pairing codes.
- Now if you look in your Control Panel/Device Manager/Ports (COM & LPT), you should see two new ports called "Standard Serial over Bluetooth link" with COM numbers after them. You'll be using the first (lower) of the two.
- Go into the APM Mission Planner and select that port, with the baud rate of 57k.
- You should now be able to connect to APM over MAVLink via Bluetooth!