This is a repository of hardware designs that have evolved out of the AuraUAS project. These designs serve the AuraUAS ecosystem.
Beaglebone Black + Custom Cape + APM2
This is the first functional autopilot board design I created myself. I have built up at least 4 flying autopilots from this design. However, it leverages the old APM2 (atmega2560-based) board as the sensor head. This results actually are quite good, but it leads to a stack of 3 boards and a fairly inefficient layout. Also the APM2 is a very old design now, has some limitations, and is only available through clone outlets.
Beaglebone Black + Custom Cape + Teensy-3.2
Although not listed as v1.5 in the file names, this is the logical successor to the APM2-based board. The APM2 is dropped and replaced by a more modern teensy-3.2 paired with an IMU/Pressure breakout board. The teensy offers much more CPU power, more memory, better ADC's, and native 3.3v ttl logic levels.
The system was breadboarded and the overall concept proved out. However, before this design was finished or built, the pocketbeagle became available. This has prompted me to move to the next iteration.
Pocketbeagle + Teensy-3.2 + Custom Board (designed with Express PCB)
This is a single board that combines a pocketbeagle + teensy + imu breakout + voltage regulator + connectors in a single board package that has only slightly larger footprint compared to the original beaglebone.
I ordered a test run of the v2.0 board and built up one to full flight status.
This board was designed with the Express PCB software which also requires ordering your boards from Express PCB. The trade off is ease of design versus flexibility and cost.
Pocketbeagle + Teensy-3.2 + Custom Board (KiCad + Oshpark)
The next evolution of the board is a redesign in KiCad. The main benefit is the ability to order the design from a multitude of board houses, and possibly even do a pick and place shop at some point in the future. This gives the most flexibility and less expensive board runs.
Oshpark is a great inexpensive option. They can suck in my KiCad pcb file directly, and they are open-source and community-sharing friendly.
Major updates:
- Switch to the awesome KiCad PCB design tool.
- Rearrange and move some parts to shrink the board footprint and simplify trace routing.
- Cleans up a few small goof ups in the v2.0 design.
- Switch to the TSR2-2450 power supply (functionally similar but slimmer and cleaner looking.)
- Add a voltage divider/sensor circuit for main input battery voltage (to complement the regulated voltage sensor.)
- Switch to a robust screw terminal connector for main power.
Pocketbeagle + Teensy-3.2 + 2 Layer Custom Board (KiCad + Oshpark)
Major updates:
- Reverse TX/RX on GPS and Telemetry ports to match drone code standard (big dohhh!!! while assembling the first v2.2 board)
- Slide screw terminal slightly towards board edge to give more space to the resistors.
- Clearly mark pin 1 on TSR2-2450 connector to help avoid assembly mistakes.
- Relocate capacitor away from corner mounting hole.
- Draw bigger usb port outlines on teensy/pocketbeagle to match reality.
- Space sbus and atto connectors exactly 0.2" from ends of PWM block.- Experiment with KiCad's autorouting feature.
- Many small component placement and trace routing adjustments for better fit and aethsetics.
These board designs support the AuraUAS autopilot flight code and firmware. The goal is to offer a relatively simple DIY "kit build" solution for fixed wing UAV autopilots. Attention is put towards using inexpensive, but powerful off the shelf components. Assembly is relatively simple (mostly 0.1" header soldering.) Overall cost is comparable to other small UAV autopilot systems.
The basic architecture of the system employs a 'little' processor and a 'big' processor working together as a distributed system. The little processor handles all the hard real time sensor I/O tasks. The big processor does all the heavy lifting, ekf, control, navigation, logging, communication, and higher level logic and functions.
This system has been developed based on experience with UAS flight control hardware, software, and flight test experience starting around 2005. There is a fair bit of thought, experience, different ideas tried, and lessons learned the hard way that have gone into the design choices, development, and tuning of this system.
The following information needs to be reviewed and updated, but is still mostly reliable.
- Maximize use of existing mature, inexpensive, and widely available sub-components.
- Minimize amount of custom electronic circuits, soldering, and cabling.
- Easy assembly/fabrication from kit (mostly 0.1" header soldering.)
- Minimize external wiring rats nest by pushing as many connections as possible onto the cape.
- High performance, high reliability, production quality flight results.
- Beaglebone/Linux based flight control system (big processor).
- Teensy/arduino based sensor interface (little processor.)
- SBUS RC Inputs (SBUS receiver required)
- 8 PWM Outputs (PWM servos required)
- MPU-9250 IMU, BMP[12]80 pressure sensor.
- 5v 2A power regulator on board.
- Attopilot (volt/amp) sensor interface for main battery.
- Avionics/main voltage sensing on board.
- Pocketbeagle console UART exposed.
- Supports industry standard (mRo) external devices: ublox 8 gps, 900mhz radio modem, i2c based airspeed sensor.
- Mature firmware, autopilot flight code, and ground station interface.
- Input power can be anything that ranges from 6.5-36 volts.
- The board includes a 5V 2A regulator to provide clean stable power for all the avionics (pocketbeagle, teensy, gps, telemetry, RC receiver, etc.)
- Servos are powered from some external source arranged by the integrator (for example from the ESC via the throttle channel.)
- Supports a variety of 5v (3.3v TTL) radio modems such as Freescale, mRo, and Digi Xtend.
- Exposes the mini-usb port on both the Teensy and the Pocketbeagle for updating firmware or debugging.
- Exposes the beaglebone UART0 (console) for additional communication and/or debugging the beaglebone.
This board is not available for sale as an assembled unit. However, you are welcome to download the design and order it through Oshpark (or any other board service.) You can purchase all the components and populate the board yourself with only minimal soldering skills. I estimate it will cost about $100/ea to assemble a full board. Most items can be purchased with free shipping.
The external components such as gps, radio modem, receiver, attopilot volt/current sensor, etc. need to be purchased separately. These are things that are required for any autopilot system.