Inav for Rovers on F4 Controllers

 I spent a lot of time trying to get a rover to work with F4 flight controllers (FC).  I thought it might be helpful to others to summarize some of my learnings:

• Inav rover software for F4 controllers often does not have all the features of Inav.  There is also no documentation of what features are not operable.  
• I could not get S.port (smartport) to work on Kakute F4 or Omni F4.  It is shown in the flight controller documentation for Betaflight, but I could not get it to work.
• The small OLED displays kind of work but the information displayed has no documentation and is often garbled.  
• Adding bluetooth via bluetooth modules is supposed to work but I could not get it working on any F4 controller.
• The FC software or the configurator will sometimes change parameters with no warning.  The first step in fixing a missing or inoperable GPS or magnetometer is to check the basic settings, the port configuration, and maybe change the setting to "auto" and force the FC to rediscover the sensor and reconfigure it.
• If you want a high level of functionality in your rover and less debugging hassle, upgrade to an F7/H7 FC.  My Kakute F7 could do proper telemetry via S.port with no trouble.  The Kakute F4 could not.
• Document your wiring
• Which UART is assigned to which function
• How are the GPS, mag, etc wired to the FC
• Establish one ground connection point and attach all sensors, FC, servos, ESC, battery to that one point.
• Don't count on the FC 5V supply to power the steering servo.  Use the ESC 5 volt supply.
• Sometimes the FC 5 volt supply relies solely on the battery, so an external 5V from a BEC will not work if it is connected to a 5V pin on the FC.
• Arming is a hassle with Inav independent of FC.  I found that it would only work when I flipped the arming switch AND held the left stick down and to the right.
• 10 series GPS work way better than 8 series.  My Beitan M8N finds 4 to 5 satellites when partially obscured.  My 10 series GPS finds 7 or 8 satellites in the same position.

Hope this helps.

INAV versus Ardupilot for Rover

I started making drones around 2011 when it was new and unregulated.  You bought a bunch of items from Hobbyking and China, read a bunch of stuff online, then experimented until your drone flew.  There were only a few expensive ready to fly drones from 3DR and DJI.

Fast forward to today and drones are highly regulated, intensely disliked by the public, and split into a few categories: racing, camera, industrial..  I have given up on drones but am still interested in autonomous vehicles, so I decided to build rovers.

My first rover is a converted Tamiya Grasshopper.  I used a Kakute F7 flight controller, GPS/compass, small OLED status display, Radiomaster TX and RX, and replaced the speed control in the Grasshopper.  

I tried it first with Ardupilot software, which I used in drones since 2011.  Wiring was a pain as I tried to keep the body of the car and add the rover functionality, which was a mistake.  With a smaller flight controller, a tight space, and a rover setup, I needed to add a separate board to allow me to change connections easily and debug.  This is the green board with the spaghetti of wires on the right side.

Ardupilot kept getting updated, and I had trouble getting it to work in rover mode, so I thought I would try Inav.  Here is what I learned:

Ardupilot

• Complex but allows for much customization.  Hundreds of parameters to set and outputs to monitor.  My previous experience helped me.
• Great documentation - you can look almost anything up.  Fair amount of videos available too.
• Good community - lots of help available
• Much easier to debug - logs available, status info on mission planner screens and onboard OLED
• Limitations if you don't use an up to date Pixhawk controller.  For example, the newest software for Kakute F7 deleted the OLED screen support.

Inav

• Simple and little support for customization.  It looks easy to get a quadcopter working but rovers are an afterthought and sometimes you need to set something up in a different way.
• Poor documentation - most of the useful information is in Youtube videos and it is frustrating to listen to 10 minutes of video to find out how to fix one simple error message at times.
• Good community - not a lot of people but they are helpful.  However, the community seems to be spread out over Reddit, Github, and Discord.
• Difficult to debug - logs only available if you pull out the SD card and read it, poor status info on mission planner screens and onboard OLED
• Lots of support for different affordable flight controllers.

If I had to do it over again, I would stick with Ardupilot.  However, it is more challenging to try and make Inav work, so stay tuned for more info.

DJI Phantom 3 Versus Custom Built Camera Drone

Anyone reading this blog (does anyone read this blog?) would know that I have built quite a few camera drones - SK450, SK450 Deadcat, S500, S500 Hexacopter.  Most of them used commercial frames, APM or Pixhawk controller, and Gopro or similar cameras.  They all worked, some of the time, and I enjoyed building them.

But I was tempted by a very low price on a DJI refurbished Phantom 3 Standard and bought it.  What was it like getting a pre-assembled and integrated drone working?  In short, very good.

I will not do a full review but just highlight the big differences between a home built drone and the DJI.

Debugging - no debugging needed, just follow the instructions, watch a few Youtube videos, update the firmware and it was ready to fly.  Contrast that with hours and hours trying to get a DIY drone working well.

Features - The DJI has more features than my homebuilts, although I could add more.  Specifically, the DJI came out of the box with failsafes, FPV, full camera control from the ground, auto takeoff and land, as well as full OSD (on screen display).

Flying - I guess DJI has a lot of experience with people crashing their drones and complaining.  The Phantom is easier to fly and has a beginner mode to keep you safe.  The auto takeoff and land also prevent a lot of crashes.

Camera - The DJI camera is pretty good, maybe not quite as good as the Gopro Hero line, but acceptable.

Accessories - Good and bad things here.  Accessories like carrying cases, landing gear extensions, and props are readily available at reasonable prices.  DJI batteries are proprietary and expensive.

So all in all a very good experience with DJI Phantom 3 Standard for about $300 USD.  If you are more into flying and photography than building and debugging, I definitely recommend it.

Quadrysteria Mini Mamba Review

Mini Mamba (Final Version)

A while back, I bought a 250 racer style kit from Quadrysteria called the Mini Mamba.  It is high quality in general, with Sunnysky motors, true carbon fiber frame, SimonK ESCs, etc.  The kit included the frame, motors, ESC, integrated BEC/power distribution card, and instructions.

I initially elected to use a Mobius FPV system, spare mini-APM controller, and Lemon DSMX receiver to complete the build.  I started trying to use the instructions, which are well written, but not very useful.  Unfortunately, there are no pictures and you are left wondering which plate is the top, what is the front, exactly what standoff is required etc.  Fortunately, there are video instructions here, and they show you exactly what to do.

In the initial build, I ran into a few problems, some of my own making.

1. The mini APM may have been defective, it did not consistently stabilize the unit.
2. The integrated power board from the kit was defective.  It did not supply proper 5V for the receiver and APM.  I had to replace it with a power distribution board and use one of the ESC BECs.
3. The wiring for the mini-APM and rest of the electronics was not reliable, probably due to the crummy wiring supplied with the mini APM.  The ESC BEC was probably not the best choice as well.

The Mamba flew, but not well, I did crash it badly enough that I had to repair it.  One of the advantages of the Mamba is that will usually just break the props and/or the nylon bolts that hold the motor mounts to the carbon fiber arms, and this is easy to repair.  Previous quads tended to break arms, props, and frame plates, necessitating major repairs that takes hours and hours.

Based on this experience,  I stripped it down and rebuilt it with an Orange receiver that I had used before, a separate BEC, and a Hobbyking mini APM and Hobbyking GPS.  The wiring was much more straightforward as the Hobbyking units came with better cables and I was using a separate BEC. It takes some work to figure out where to stick the ESCs, cabling, BEC between the top and bottom plates.

Side view

Performance is much better but there is still a lot of tuning required as it is very sensitive to pitch and roll, but very insensitive to throttle.  Some other pictures are shown below.

Arm assembly which is set up for easy repair after crashes

Mobius FPV setup with integrated mount and transmitter.  This will be reviewed in future.

Converting the Eachine Racer 250 to APM Controller

A while back I wrote about buying the Eachine Racer 250, which used a CC3d controller.  Well I got tired of trying to figure out this controller and decided to switch the controller over to an APM.  I used the Hobbyking Micro APM, but you can get the same hardware from Banggood.

This started out easily enough, but there were a few hurdles along the way.

Step 1 Disassemble the Eachine

Take the top deck and battery alignment plates off as shown in the figure 1.  Be careful when removing the power connector for the 5.8 GHz video transmitter as it can be easily damaged.  Use an old coffee cup to store the parts while you work on the rest of the project.

Figure 1

Step 2 Mount the Micro APM

The Micro APM will easily go into the CC3D mounting standoffs as shown in figure 2.  Note that you will have to remove one standoff that supports the battery alignment plate as it blocks the USB port.  Figure 3 shows the APM mounted from the top

Figure 2

Figure 3

Step 4 Wire Up the APM

Here is where it gets a little tricky.  The servo wiring from the APM to the receiver is done as per normal.  The Ardupilot.com website shows how it needs to be done.  This is easy.

Next, you need to supply power to the APM so you will need to make up a cable that goes from the Eachine 5V and ground power pads (green arrow Figure 4) to the power input connector of your APM (magenta arrow, Figure 4). You will need a 6 pin connector to attach to the APM.

Then, we come to the tricky part.  The connections to the motor speed controls are shown by the red arrow in Figure 4.  You have to make a new cable here.  The motor numbering IS NOT THE SAME for APM and CC3D.  The cable will need to be set up as follows:

APM            Eachine

5V                5V

Gnd              Gnd

Motor 1        Motor 2

Motor 2        Motor 4

Motor 3        Motor 1

Motor 4        Motor 3

Figure 4

Step 5 Reaasemble the Eachine

Now you can reassemble the battery alignment plate, top deck, and secure any loose wires.  You are ready to fly again after the usual ESC calibration, radio, compass, gyro calibration are done.

Figure 5 Reassembled Eachine Racer 250

Hexacopter First Flight

I managed to get the Hexacopter to fly after a few flips on takeoff.  It turns out that the motor configuration and wiring for a Pixhawk is not intuitive or well documented.

1. You have to search through DIYdrones forums to find the information here.
2. Connect motors 1 to 4 to Pixhawk inputs 1 to 4, same as a quadcopter.
3. Connect motor 7 to Pixhawk input 5
4. Connect motor 8 to input 6

Bingo!

Quad to Hex

I decided to go further and build a hexacopter.  I was able to use my existing 550 quadcopter parts and purchase an inexpensive hex frame from Banggood.com, two more motors, two more ESCs, and use some extra landing gear parts.  Here is what I have so far:

Flysky i10 PPM

A while back I reviewed the Flysky i10 radio.  It is a great radio for the price, but I needed PPM output from the receiver in order to feed my Pixhawk.  PPM is a single wire interface for all channels, in place of the one-cable-per-channel PWM interface, which is about 40 years old.

The manual tells you nothing about how to do this, but the online forums were filled with people saying it could be done.  I tried everything, and could not find a way to do it.

Finally, I found a bunch of postings about a very helpful fellow at Diamond Hobby, Jim Ogorek, who might be able to help (email: jim@diamondhobby.com).  In spite of the fact that I bought the radio through another retailer, Amazon, he helped me by sending me the update software for the radio.  Note that there are two versions, US and China.  I needed China because my radio showed up as a "CN" device on windows.

After running the software on my PC and connecting up the radio, I was able to update the transmitter, and it then updated the receiver, and bingo, I had PPM!  You go to the receiver menu on the transmitter and there is a simple check box for PPM and it enables PPM output on ch1 of the receiver.  Works like a charm.

Eachine Racer 250 - How Does Openpilot Compare to APM/Pixhawk

I saw a good deal on Banggood.com for a small ARF (Almost Ready to Fly) Quad called the Eachine Racer 250 and went ahead and purchased it.  It is a 250 sized unit with the FPV built in, includes a battery, and charger, and cost around $125.  I added a spare Orange DSMX receiver and a Spectrum DX4e transmitter and was up and running!  It sends video to my 5.8 GHz integrated receiver-monitor and works like a charm.  Build quality is good for the price, packaging was good, and it is designed well.  As usual, there are NO INSTRUCTIONS from the Chinese manufacturer in the box and you have to hunt around on the web to find out how to set it up.  I found a few good Youtube videos and they guided me through setup without a problem.

The only thing that was challenging was my lack of knowledge of the flight controller, the CC3D, an open source flight controller that is somewhat different from the APM or Pixhawk.  I again queried the web and found the ground controller for Openpilot, which supports CC3D hardware.  I downloaded the software, installed it, connected USB to the quad, and followed the instructions in the video.

The quad flew, but was very sensitive to control inputs, too much for my flying skill.  I again went to the web, found some tutorials, and tried to fix the settings.  The tutorials were out of date so I went to the wiki, which seems to be permanently down.  I then posted a question on RCgroups.com and got some information.

Unfortunately, there seems to be a schism in the Openpilot community and it has split into three factions: Taulabs, Librepilot, and Openpilot.  While Openpilot works, it does not seem to have as much support as it used to.  The other 2 options seem to be works in progress.  APM and Pixhawk/PX4 are definitely better options if you have a choice.

But I did figure out how to desensitize the quad using the current Openpilot and it flew well in a couple of outdoor test flights.  Stay tuned for more info.

Short Review: Olympus Air as Drone Camera

As a dedicated Micro 4/3 Mirrorless camera user, I thought it would be great to try the new Olympus Air A01 camera.  This is similar to a product put out by Sony which attached a photo-quality lens to a Smartphone.  However, the unique ability of the Olympus Air is that it will take any interchangeable Micro 4/3 lenses.  Price is low: approximately $299 street price in USA for body only.

Olympus AIR A01

I received the AIR yesterday and rushed to get it charged (about 4 hours) and get it set up.  It is not a perfect product and there are a few warts, some of which could be fixed in future software.  The cylindrical body of the AIR is quite small and light, and it communicates with your IOS or Android device via Bluetooth and Wifi.  This has some issues as you disconnect from your home wifi to access the AIR wifi, as the AIR sets itself up as an access point.  You also have to download the correct Olympus AIR app, and set a few things up.  The normal mode of use is to clip your smartphone to the back of the AIR and use it as a viewfinder and remote control.  I tried this and it works as advertised.

The AIR has the following useful qualities for drones:

• Professional quality sensor (16MP) and lenses, Full HD at 30 fps
• No added functions, buttons, screens, & grips which are normally part of a photo quality camera - you don't have to lift a whole DSLR to get Photo quality
• Tripod mount - invaluable as you can easily adapt it to existing gimbals and mounts
• Interchangeable lenses
• Autofocus, image stabilization, face detection, long list of DSLR type features
• Ability to turn off wireless connections so they do not interfere with drone radio control
• Built-in battery
• Light - I measured 368 gm for the AIR with a Panasonic 14-42mm zoom lens, which is not the lightest 4/3 lens by any means.  The AIR alone is about 150 gm.
• Open API interface so software could be written to control the camera and lens in flight

I rushed to get it installed on my test mule drone, an SK450 Deadcat.  I found a tripod mount that attached to my existing Gopro mount, but it was not ideal as it mounted the AIR too high and too far forward, but it sort of worked (see photos).

There are a few drawbacks to the AIR, which I will list below, mainly concentrating on drone-specific items:

• The setup is complicated, you have to read the instructions carefully and follow them
• The app is not intuitive, some updates needed here
• Wifi video transfer to smartphone takes a long time for some unknown reason, about 10 minutes for a 3 minute video.  I recommend connecting the AIR via USB to your PC where the transfer took about a minute.
• You have to keep your smartphone hooked up to the AIR by wifi and bluetooth, and the smartphone will try to go back to its home network if you turn off the AIR or connection is lost, causing you to have to go back to the setup menu and reselect the right networks again.

Olympus AIR with Panasonic 14-42mm lens

SK450 Deadcat with AIR

Closer View of Not-So-Great Mount

Always Keep Two Quadcopters

I learned again that it is a good idea to have two quadcopters:

1. One to fly
2. One that you crashed and is being repaired

Another important lesson was not to fly near trees, as Quadcopters Love Trees.

Quanum Q-2D Brushless GoPro 3 Gimbal Test

Gimbal Mounted on S500 Quadcopter

Attached a 2D camera gimbal to the drone and did a quick test flight with my Gopro Hero3+ Black.

The included Gimbal mount on the S500 frame was not useable as there was only about 1-2 cm of clearance between the bottom of the gimbal and the ground and I was sure that the gimbal would be damaged in a hard landing (see previous review of the S500 frame).

The gimbal is the HobbyKing Quanum Q-2D Brushless GoPro 3 Gimbal.  I could not get it to work attaching the gimbal controls to the Pixhawk so I connected the servo cables to the FlySky i10 receiver directly.  The only adjustment was limiting the maximum throw on the transmitter for the gimbal controls to +/- 30%.  This makes the gimbal less sensitive to the movement of the rotary controls on the transmitter.

Successful indoor Test Flight is shown below:

Unsuccessful outdoor test flight (gimbal worked, quadcopter not so much) is also below:

Hobbyking S500 Frame Review

S500 Quadcopter

I am building a new quadcopter for higher quality photography using the hobbyking s500 frame, which is similar to the sk450, but slightly larger.  It is now flying and I can comment on its pros and cons.

Pro

• Slightly stiffer arms than Sk450
• Plenty of space for electronics
• Higher landing gear to allow for camera gimbal
• Adjustable mount for gimbal - can shift gimbal forward and backward 
• Integrated pcb for power distribution 
• Spare parts available
• Low cost 

Con

• Landing gear not too sturdy 
• Landing gear too low to use included adjustable mount with 2 axis gimbal, have to hard mount to pcb

Note Top of Landing Gear, too flexible, not well attached to frame

I used sunnysky 2212 motors and they are much better than the turnigy motors on the SK450 - powerful, quiet, less vibration, smaller. I was also able to use my pixhawk controller which would not interface properly to the turnigy plush ESCs when I tried it on the SK450. For the S500 build, I used low cost Spider ESCs with SimonK firmware, which worked well with the pixhawk. Carbon fiber props and the previously reviewed Flysky i10 radio rounded out the build. 

First outdoor test flight is shown below. 

Summary 

The S500 is a good frame for a camera quadcopter, but it is not recommended for a beginner builder. Modifications are needed for camera mounting, the landing gear, and perhaps for power wiring so it helps if you have some experience with building  quads. 

S500 fully assembled with Gimbal, Telemetry

Flysky i10 Review

I recently bought the Flysky i10 radio for my latest quadcopter project.  I love this RC unit.

The system, as delivered, includes the transmitter with rechargeable battery, receiver, external voltage sensor, rpm sensor, and temperature sensor along with a useful manual on CD.  The manual is actually well written and useful, unlike many Chinese radios.  Build quality seems good, no obvious cheap parts or poor assembly.

Transmitter

The transmitter has a touch screen interface, somewhat Android-like, and it is easier to use than the older text menu driven systems.  You can set up almost anything through the interface: limits, mixes, switch assignments, delays, failsafes, etc.  The transmitter itself is slim, with rubberized grips, making it easy to hold.  There are many different switches and knobs which can be attached to any channel.  This was great for the quadcopter as you could get 2, 3, or more flight modes on one switch or knob without using cumbersome control mixing.   Camera gimbal control is also easy with the two variable control knobs on the top corners of the transmitter, easily manipulated by your index fingers while your thumbs work the joysticks. Joystick feel is good.  The transmitter can also be programmed via USB, which I have not tried yet, and it also has an SD card for storage.  Telemetry data from the receiver and sensors is shown on the transmitter LCD display.

Home screen

Icons for customizing transmitter

Receiver

The ia10 receiver has 10 channel ports which work well with my Pixhawk and standard servos.  It also has an "Ibus" which can be used to output PPM (I have not figured this out yet), or take inputs from the telemetry sensors.  Ibus documentation is not great, so check back in a while and see if I can figure out how to use it for PPM and other purposes.  Range seems very good in my experience.

Receiver as installed on my Quadcopter

Testing

I installed the system on an S500 quadcopter and used a generic PPM converter to generate PPM for my Pixhawk controller.  It was relatively simple to set up the control functions, map the flight modes to a three position switch, and range check the system.  Performance during test flights and a long hot outdoor flying session was excellent.

Summary

I highly recommend this radio for quadcopters and believe it will also be an excellent choice for airplanes, traditional helicopters, and other vehicles.  The price, about $200 US, is unbeatable for the value received.

Sensors included with the System

First Successful Quadcopter Autonomous Mission

After all the adjustments to the Deadcat SK450, I took it out to the local "park" (remote muddy field) to try a mission.  It was a simple mission, fly to a few waypoints, circle at one waypoint, return to launch, then land.  It actually worked!  Here is the video:

Getting Telemetry Working, A Short Review of Excelvan Radio Telemetry Kit 915Mhz

I recently purchased a small Telemetry module from Newegg.com for about $25, it runs on the unlicensed 900 MHz band.  It was quite easy to hook it up to my Hobbyking Micro APM and now I can monitor the Quadcopter while in flight, just as if it was connected to my PC via USB.  No need to connect USB on the ground, as this telemetry connection handles all communications.

A new cable must be made using the supplied telemetry cable from the telemetry module and the one supplied with the APM.  Also remember to connect as follows:

Telemetry Module with black antenna

Telemetry Module	APM
5V	5V
Gnd	Gnd
TX	RX
RX	TX

The PC connection was also painless, stuck the module into a USB port and the driver loaded automatically onto my Windows 7 laptop.

The only other trick is to select 57.6Kbps in Mission Planner to get the link to work.

Note: Telemetry module is from Excelvan and is called "Radio Telemetry Kit 915Mhz Module for APM APM2.5 2.6 Pixhawk PX4 RC Multicopter Quadcopter" and is available on Newegg.com

Update-Pixhawk Test

I also purchased a unit for use with my Pixhawk-S500 quadcopter covered elsewhere on this blog.  This time, I could use the included cable to connect the telemetry unit to my Pixhawk, although I had to shave a little plastic on the Pixhawk end, as the Pixhawk uses unusual connectors.  As with the APM, I set the rate to 57600 and was connected to Mavlink on the Pixhawk.  Works like a charm.

More Fixes to the SK450

I am plagued by poor loiter on the SK450 and have made further changes to improve things:

1. Fixed the slop or wobble in the GPS mast.  It turns out that the cheap mounts rely on being able to screw down the knurled flange until the mast mount inside is snug.  However, a lot of them cannot be tightened.  I added a plastic washer from an old prop to the mast as shown and the wobble stopped.
2. The APM mount was maybe moving in flight, so I remounted it with the special vibration reducing foam rubber and I secured the USB cable better so it could not move the APM.
3. Added a little foam rubber inside the micro APM case to ensure the barometers were not getting fooled by the prop wash.
4. Wait 5 minutes after power on to get the GPS and all sensors stable before trying a flight.
5. Added some practice golf balls to the landing gear so they do not catch in the grass when taking off or landing.
   
6. I very carefully recalibrated the accelerometers, making sure that the quad was absolutely level during the first stage of calibration.  This made a HUGE difference versus my previous "it looks level" calibrations - the test flight was much beter with much less yaw and pitch on takeoff and during flight.
7. Made a stand out of a medium size plastic storage container as shown:

Pixhawk Versus APM Comparison Review

This blog entry compares two flight controllers from the Ardupilot 3DR-Open-Source stream: the generic APM 2.X controller and the Pixhawk.  I am an intermediate multirotor builder and flyer, so this comparison will focus on functionality and useability, not on advanced features.  Also, this review is based on my experience with 5 different APM modules (none sourced from 3DR) in three different physical forms: standard, mini, and micro (also called mini by some) sourced from Hobbyking and generic Chinese manufacturers.  The Pixhawk is available from multiple domestic and Chinese sources and you should check the reviews to make sure you are getting one with decent build quality.  Each was used with corresponding GPS/Compass units from the same manufacturers.  I built three different quadcopters and used them with different controllers.

Feature/Characteristic	Generic APM 2.X	3DR Pixhawk	Comment
Size/Weight	Small	Larger	APM is available in 35x35x5 mm board.  Pixhawk is 81x50x16 mm
Cost	Low	Higher, about 4X	APM with GPS ~$65
Quality	Variable	Better	Inspect a generic APM after you get it for poor soldering, loose USB..
Support	Good	Good	The best support is from peers on DIYdrones and APM forums
Flight Stability	Good	Good	This is my experience with a well setup APM and Pixhawk, your experience may vary
Accuracy	Good	Better	It does depend on your GPS and its accuracy.  Pixhawk has a more powerful processor and more memory
Onboard indicators	Poor	Good	Pixhawk has multiple LEDs and tones to tell you status, APM has a few LEDs
Ease of Setup	Moderate	Moderate	More components to interconnect on Pixhawk, but well documented. Cables and connectors often an issue with APM and documentation must be found on the Internet.
Ability to fly autonomous missions	Yes	Yes
Mission Planner Ground Station Compatibility	Yes	Yes
Flight logging Capability	Good	Better	Pixhawk logs more information and has a microSD for storage. APM has limited storage of most important variables.
Upgradeability	None	Yes	APM code is now frozen to my knowledge, but Pixhawk software with improvements still being released
Debugging difficulty	Good	More difficult	APMs seem to always work, Pixhawk is more finicky about ESCs, setup, etc.

Overall, both controllers are excellent and have worked well for me.  The APM is a better fit for small quadcopters and is probably better for the beginner builder due to its simpler setup and low cost.  The Pixhawk is very good but it takes more time to set up and it is likely higher quality and performance, so it works well in larger camera quadcopters and similar expensive vehicles.

APM equipped SK450 "Dead Cat" Quadcopter

S500 Quadcopter with Pixhawk

Fixed the Loiter

Well I fixed the Loiter problem, the quadcopter will now hold position and altitude on command.  The changes were detailed in the previous blog post

1. Put in a new GPS.  
2. Improve power feed to the controller and receiver by using a UBEC (battery eliminator) instead of the power feed from the ESCs.  
3. Get rid of extra wires in the controller wiring harness.
4. Performed an indoor test flight and analyzed logs.  
5. Performed an outdoor test flight which was successful.

I also included a parameter change:

- changed INS_MPU6K_FILTER from 0 to 20 to filter out barometer fluctuations

Further Enhancements

After the exciting flight last week, I had to repair the Quadcopter as one of the arms broke in a landing.  So I decide to make a few enhancements:

1. Put in a new APM controller and GPS to fix the Loiter issue.  This did not turn out well as the new controller was defective but the GPS seemed to improve things.  The new GPS is Hobbyking brand, old one was a "no-name" with some mods to make the cable work.
2. Improve power feed to the controller and receiver by using a UBEC (battery eliminator) instead of the power feed from the ESCs.  This is recommended due to the interference from the ESC and I do think  it improved things.
3. Get rid of extra wires in the controller wiring harness.  Done.
4. Install new arm.  Did this, I learned from the dearly departed Flying Flowerpot quadcopter that it is almost impossible to properly fix a quad's arm and they are reasonably cheap.
5. Performed a test flight and analyzed logs.  Seemed to improve things with few glitches on barometer and GPS and more stable flight.  Testing will continue.