Yet Another Autopilot

It seems everyone and their mother has an autopilot board they're working on so I thought I would join the bandwagon. I've actually been wanting to develop one for quite some time, but after seeing Bill and Paul's progress on their DCM estimation work I got inspired to get started now.There are several good autopilot boards available for experimentation, but none that had the feature set I was looking for. I wanted something versatile enough to be used in several controller/data logging applications including those involving RC cars/boats/copters/planes as well as high altitude ballooning and rocketry. With this versatility comes a little more complexity, so this might not be the board for someone just starting out, but for others I hope it will be a good platform to work with.Here are a few specs/features.Pic32 based -> An inexpensive chip ($8 or less) with respectable horsepower (32 bit 120 DMIPS) and free development tools. An inexpensive programmer can be had from Sparkfun and others.Micro SD Card based Data logging-> Lots for storage for logging every aspect of your flight. Can also be used to read way points or other mission data.USB Interface -> Useful for uploading/downloading mission data, payload control and as a bootloader for program updates.Real Time Clock -> Time tag logged data or perform time based mission functions.5 PWM Inputs and 5 PWM Outputs -> Interface to existing RC Rx outputs and drive up to 5 standard RC servos.On Board 3 Axis Accelerometer -> 12 bit resolution + Software control of sensitivity (1.5G, 2G, 4G, 6G).On Board 3 Axis Gyro-> 12 bit resolution + Software control of sensitivity (110 deg/sec or 500 deg/sec). family of pin compatible gyros from 67deg/sec to 2000 deg/sec.On Board 3 Axis Magnetometer.GPS Interface -> UART based interface with option of 5V or 3.3V power.Radio Modem Interface -> UART based interface with option of 5V or 3.3V power.Battery Voltage and Current Monitoring. Up to 24 Volts and 50 Amps.On Board 3.3V and 5V regulation -> Plenty of current capability to handle heavy servo loads and RF Modem power requirements.Lots of digital and analog IO -> IR and Sonar based range finder interfaces. Airspeed and Altitude interface. I2C, 8 bit data bus + discrete digital IO.This design will be completely open source, and below you will find a link to the preliminary schematic. I will start on the layout next and hope to have it completed and ready to send in for fabrication on May 4. I look forward to comments/suggestion on the schematic. Also if anyone is interested in getting one of the prototype PC boards when I have them made please let me know. Bare in mind however that this is a prototype and I can make no guarantees that there won't be some boo boos. The parts are small and surface mount, so if your not an experienced assembler you might want to take this into consideration.Although not always the cheapest, I have always had good luck with Advanced Circuits for PC Board fabrication. The cost for 1 week turnaround is $66.00 per board (4 layers) +shipping.I'll post a complete parts list in a week or so when I finish the layout.Software development will follow. I plan on quickly implementing a shell to handle all the timing and IO interfaces, followed by a gradual implementation of the various controller tasks hopefully with community support.Looking forward to comments.Regards,Brianpic32_autopilot_schematic.pdf
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  • WOW great progress! Looks like you are doing telemetry with an RF serial link (Xbee?), so my comment on OSD is just to get a video link capability.

  • T3
    Hey John,
    Project is going great. Take a look at the other posts.

    Attitude Estimator Video
    Prototype Built
    Layout Done.

    I hadn't thought much about doing the OSD in the vehicle, I always sort of thought I'd do it on the ground station. I'll take a look at the OSD chip you listed though and see what would be involved.

  • Hi Brain

    Just wondering how your project is going.

    Also wondering if you plan to incorporate any OSD capability, such as an onboard MAX 7456 IC? I think there is a lot of interest in this capability and integrating it would save a lot of interface hassles and be more compact.

  • Thanks Brian

    I will keep an eye on this thread with great interest.
  • T3
    Hey John,
    Yes, I'm sure we could work something out. If there is a lot of interest in pre-assembled boards then I can look into having some boards assembled by a production house, otherwise if it's just 1 or 2 I can build them up myself.

    Not sure about cost yet. It's looking like parts come in about $180 in small quantities + tax and shipping. Some parts could be left off at first if they're not needed such as the magnetometer or airspeed indicator. That could save a fair amount on parts. The boards in prototype quantities are $70. Since I hand solder instead of the solder past/hot air method, assembly can be a little time consuming. I'll throw out $350 total, but don't hold be to it just yet until I've built the first one up.

    Thanks for the interest,
  • Do you think an assembled board would be possible in the future? Cost? I'm a little surface mount solder impaired:)
  • T3
    Great Garth, we'll both be learning along the way.

  • Brian
    looks really great and I would like to work along and learn as much as I can as we go if that okay with you,
    many thanks
  • I can recommend the ChipQuik solder paste syringe + $20 electric skillet reflow process described @ SparkFun. I'm doing 0.5mm LQFP48 and LGA28 (ST gyro) successfully with this on homemade PCBs w/o a solder mask. I cut a low-quality stencil out of office paper, apply the paste, remove paste b/t the pads with a hobby knife, and reflow. Usually requires some touch-up with an iron afterward, but still much faster + easier than doing it part-by-part with a $$$$ hot air station. Sane people just pay fab/assembly houses, but if you're insane/cheap/impatient DIY is great.
  • T3
    The processor is in a TQFP package. Some of the sensors are in LCC packages that can be a little tricky. The hot air should work fine, just make sure not to overheat the parts. You should be able to fine some tutorials on the internet.

    My design is open source, so feel free to incorporate any aspects of it you like into your board. I will be posting the parts list in the next day or so, so you can see what I used and what packages they are in.

    I've used Eagle in the past, but I do most of my work in Orcad.

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