Modems

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The Paparazzi autopilot features a 5V tolerant 3V TTL serial port to interface with any common radio modem. The bidirectional link provides real-time telemetry and in-flight tuning and navigation commands. The system is also capable overlaying the appropriate protocols to communicate thru non-transparent devices such as the Coronis Wavecard or Maxstream API-enabled products, allowing for hardware addressing for multiple aircraft or future enhancements such as data-relaying, inter-aircraft communication, RSSI signal monitoring and automatic in-flight modem power adjustment. Below is a list of some of the common modems used with Paparazzi, for details on configuring your modem see the Airframe Configuration page.

Maxstream XBee Pro

These relatively cheap and light modules implement the ZigBee/IEEE 802.15.4 norm. They allow up to 1 mile range(Paparazzi tested to 2.5km). The main drawback of using such 2.4Ghz modules for datalink is that it will interfere with the 2.4Ghz analog video transmitters and a inevitable decrease in range when in proximity to any wifi devices.

XBee Pro USB Stand-alone Modem (XBP24-PKC-001-UA)
  • Frequency Band 2.4Ghz
  • Output Power 100mW (Xbee Pro)
  • Sensitivity -100 dBm
  • RF Data Rate Up to 250 Kbps
  • Interface data rate Up to 115.2 Kbps
  • Power Draw (typical) 214 mA TX / 55 mA RX
  • Supply Voltage 3.3v
  • Range (typical, depends on antenna & environment) Up to 1500m line-of-sight
  • Dimensions 24 x 33mm
  • Weight 4 grams
  • Interface 20-pin mini connector
  • Chip antenna, ¼ monopole integrated whip antenna or a U.FL antenna connector (3 versions)
  • price : ~32$
XBee Pro OEM Modem

Pinout

Maxstream XBee pinout


Documentation

Maxstream 9XTend

These larger units have been tested on the 900Mhz band, but are also available in 2.4Ghz. They are a bit on the heavy side(~20grams) but give good performance at range. They have adjustable power settings from 100mW to 1W. Testing has shown range up to 2 miles with 100mW.

9XTend USB Modem
  • Frequency Band 900Mhz and 2.4Ghz (2 versions)
  • Output Power 1mW to 1W software selectable
  • Sensitivity -110 dBm (@ 9600 bps)
  • RF Data Rate 9.6 or 115.2 Kbps
  • Interface data rate up to 230.4 Kbps
  • Power Draw (typical) 730 mA TX / 80 mA RX
  • Supply Voltage 2.8 to 5.5v
  • Range (typical, depends on antenna & environment) Up to 64km line-of-sight
  • Dimensions 36 x 60 x 5mm
  • Weight 18 grams
  • Interface 20-pin mini connector
  • RF connector RPSMA (Reverse-polarity SMA) or MMCX (2 versions)
  • price : ~179$
9XTend OEM Modem

Pinout

Maxstream 9XTend Pinout
9XTend 20-pin Header Name Tiny Serial-1 Header Notes
1 GND 1 (GND) Ground
2 VCC N/A (requires 5V) 5V power (150mA - 730mA Supplied from servo bus or other 5V source)
5 RX 8 (TX) 3-5V TTL data input - connect to Tiny TX
6 TX 7 (RX) 5V TTL data output - connect to Tiny RX
7 Shutdown N/A (requires 5V) Permanently connect this pin to the 5V bus for normal operation

Notes:

  • 9XTend can run on voltages as low as 2.8V but users are strongly advised against connecting any modem (especially high power models) to the sensitive 3.3V bus supplying the autopilot processor and sensors.


Documentation

Aerocomm

Aerocomm's API mode is not yet implemented. Therefore they are used in transparent mode. Users are reporting these modems cause more interference with GPS reception then the Maxstream modem.

AC4868-250

  • Frequency Band 868MHz (For Europe).
  • Output Power (w/ 2dBi antenna) 250 mW
  • Sensitivity (@ full RF data rate) -103 dB
  • RF Data Rate Up to 28.8 Kbps
  • INterface Data Rate Up to 57.6 Kbps
  • Power Draw (typical) 240 mA TX / 36 mA RX
  • Supply Voltage 3.3v & 5V or 3.3v only
  • Range (typical, depends on antenna & environment) Up to 15 kilometers line-of-sight
  • Dimensions 49 x 42 x 5mm
  • Weight < 21 grams
  • Interface 20-pin mini connector
  • Antenna MMCX jack Connector
  • price : ~80$
Aerocomm USB Stand-alone Modem

AC4790-200

  • Frequency 902-928MHz (North America, Australia, etc).
  • Output Power 5-200mW
  • Sensitivity (@ full RF data rate) -110dB
  • RF Data Rate up to 76.8 Kbps
  • INterface Data Rate Up to Up to 115.2 Kbps
  • Power Draw (typical) 68 mA
  • Supply Voltage 3.3v & 5.5V
  • Range (typical, depends on antenna & environment) Up to 6.4 kilometers line-of-sight
  • Dimensions 42 x 48 x 5mm
  • Weight < 20 grams
  • Interface 20-pin mini connector
  • Antenna MMCX jack Connector or internal
  • price : ~80$
AC4868 OEM Modem

AC4790-1000

  • Frequency 902-928MHz (North America, Australia, etc).
  • Output Power 5-1000mW
  • Sensitivity (@ full RF data rate) -99dB
  • RF Data Rate up to 76.8 Kbps
  • INterface Data Rate Up to Up to 115.2 Kbps
  • Power Draw (typical) 650 mA
  • Supply Voltage 3.3V only
  • Range (typical, depends on antenna & environment) Up to 32 kilometers with high-gain antenna
  • Dimensions 42 x 48 x 5mm
  • Weight < 20 grams
  • Interface 20-pin mini connector
  • Antenna MMCX jack Connector
  • price : ~80$

Pinout

Aerocomm AC4868 modem pinout
Aerocomm AC4490 wiring example


Wiring the Aerocomm AC4868 to the Tiny
AC4868 20-pin Header Name Color Tiny Serial-1 Notes
2 Tx green 7 (Note 1)
3 Rx blue 8 (Note 1)
5 GND black 1 -
10+11 VCC red 2 +3.3v
17 C/D white 3 Low = Command High = Data

Note 1 : names are specified with respect to the AEROCOMM module

Documentation

Radiotronix

These Radiotronix modems are used in transparent mode. Use the WI232EUR Evaluation Software for configuring the modems for the set speed. Connect /CMD and CTS for programming. The DTS version for the US market might cause severe interference with GPS reception, it is not recommended.

WI232EUR

  • Frequency Band 868MHz (for Europe)
  • Output Power 32 mW
  • RF Data Rate Up to 76.8 kbps
  • Interface Data Rate up to 115.2 kbps
  • Power Draw (typical) 65 mA TX / 20 mA RX
  • Supply Voltage 3.3v
  • Range (typical, depends on antenna & environment) 500 meters line-of-sight
  • Dimensions 24 x 21 x 4mm
  • Weight ~2 grams
  • Interface solder connector
  • Antenna solder connector
  • price : ~25$
WI232EUR Modem

Pinout


Wiring the WI232EUR to the Tiny
WI232 pins Name Tiny Serial-1 Notes
6 TxD 7 (Note 1)
5 RxD 8 (Note 1)
15-18 GND 1 -
19 VCC 2 +3.3v
4 /CMD - (Note 2)
7 CTS - (Note 3)

Note 1 : names are specified with respect to the Radiotronix module

Note 2 : connect to RTS to program device with Evaluation software

Note 3 : connect to CTS to program device with Evaluation software

Documentation

Coronis WaveCard

These relatively inexpensive and light modules implement a Coronis proprietary protocol. Low power consumption - high latency - I would not recommend these modules mostly because of the low quality of the distribution and support. The documentation is rather poor and not easily available.

  • Frequency Band 400MHz, 868Mhz and 915MHz (3 versions)
  • Output Power 25mW and 500mW (2 versions)
  • Sensitivity -110 dBm (@ 9600 bps)
  • Data Rate 100 Kbps
  • Power Draw (typical) 45mA (25mW), 450mA (500mW) TX / 15 mA RX
  • Supply Voltage ...
  • Range (typical, depends on antenna & environment) Up to 1km (25mW) , 5km (500mW) line-of-sight
  • Dimensions 30 x 28 x 7mm (25mW), 37 x 30 x 7mm (500mW)
  • 50 ohm RF port for antenna connection

Coronis Wavecard

Documentation

Video Transmitter Telemetry

2.4GHz Video Transmitter

In order for the UAV to transmit video from an onboard camera, a video transmitter is needed. The paparazzi AP sends all telemetry data down with the video on the audio channel portion of the transmitter. This means that the transmitter must have an audio channel. These vary in power, and thus range, and run normally on 2.4Ghz. Small UAVs can get about 600m of range from the 50mW version, and extended range can be achieved using units up to 1W. Weight for these units varies from a couple grams to about 30 for the 1W with shielding. Please check for your countries regulations on 2.4Ghz transmission, as each is different.

Antennas

Here are some examples of lightweight and efficient 868MHz antennas developped by the RF laboratory at ENAC.

868MHz copper foil antenna attached to the aircraft tail
868MHz copper foil antenna bottom view
868MHz ground antenna