Someone once told me: “If you aren’t ashamed of your first release, you waited too long”, so here it is: https://github.com/niobos/velbusd

The initial flash

After reading through the dd-wrt forum (most notably this one) and the wiki page, I learned a few things:

• Recommended build is still 14929
• This unit needs a tailored build for the first flash

This is the procedure I followed, with success, starting from Linksys version “2.00.00 B05 Jul. 10, 2009″:

1. Download the tailored build for the WRT610N (local copy) (for the freaks, my binary MD5s to c67e6099c63f11cc8e8f5f74b371aa23).
2. Connect via wired ethernet to the router. That way, you can see the link going up/down.
3. Reset the Linksys software (defaults are 192.168.1.1, username “” and password “admin”)
4. In the Linksys firmware, upload this file.
5. Wait 5 very long minutes.
6. Configure yourself a static IP in the 192.168.1.0/24 network (I use 192.168.1.8)
7. Direct your browser to http://192.168.1.1/
8. You may have to set a temporary password, I did not.
9. Wait 1 minute
10. Reset the router: push & hold the reset button, wait 30 seconds; unplug the power, wait 30 seconds; plug in power, wait 30 seconds; release reset button.
11. Close & reopen your browser to flush all cached pages and credentials
12. Direct your browser to http://192.168.1.1/. If you don’t get the question to set up a new password, the reset didn’t work.
13. Enjoy

The upgrade

After the initial flash, you can upgrade to any regular version, but keep in mind that this unit requires a 2.6 kernel. I choose the 14929-mini version (local copy, md5 af9ab2ff822ab69d26fa7308d47ad05a), not because it provided all I need (it doesn’t support IPv6 for example), but because it leaves the most free space for me to fiddle with.

To switch versions, I always follow this overly cautious procedure: (if you do this right after the initial flashing, you might be able to skip straight until step 4)

1. Reset to defaults: reset, 30 seconds; power down, 30 seconds; power up 30 seconds; release reset.
2. Make sure your IP is in the correct range (192.168.1.0/24)
3. Set a temporary password
4. Upload the new firmware
5. Wait until the browser is again at the “Set password” page (or 5 minutes)
6. Set temporary password (again, I did not get this prompt)
7. Reset to defaults again

I double-checked the gyro direction, the control direction and the direction of rotation; all seem to be correct. Until I took a closer look at the tail rotor itself:

The tail rotor hub had moved 6mm from the end of the shaft, and the set screw was gone. Moving the hub back into position was hard, it was jammed fairly hard.

Hardware & 3GX setup

Setting up the collective & cyclic pitch ranges is a bit more complex with a 3GX added to the mix. Obviously, you can switch the 3GX into bypass mode called “DIR” mode. This disables the 3 gyro-feedback loops and lets you control the servo’s directly. You can enter “DIR mode” by powering on the 3GX with its button depressed, and releasing the button as soon as the LED’s start cycling.

First thing to do was to set up my Tx into the correct CCPM mode: “SR-3″. To get the correct direction of movement, the aileron and elevator servo’s needed reversing. Since the three servo’s are identical, I did not need any specific end-point adjustments and left them all at 100/100. The neutral points were reasonably well set up mechanically, but still needed some fine-tuning with the “sub-trim” to get the swash absolutely level (Ail -22, Ele +6, Pit -12). I configured a collective pitch range of -12º to +12º by reducing the “Swash AFR – Pitch” to +30%. For cyclic pitch I set up ±9º (Ail -47%, Ele +47%).

After teaching the Tx the proper configuration, I also needed to configure the 3GX with the same info. This mostly boils down to setting the 3GX in the correct learning mode and moving a specific control on the Tx to copy the settings.

ESC setup

I kept the original settings for the archives. I configured the input voltage, pole count and gearing ratio into the software, which told me I should use the high speed governor mode. I left most of the other settings at the default. Here is the result in binary and readable form.

Tx setup

Finally I configured some features of my transmitter such as Fail/Safe and Expo. I’m too lazy to text-ify it all, so here’s the full config:

• D/R,EXP
• CH 1 (AILE), CH 2 (ELEV) & CH 4 (RUDD)
• No UP & No DN
• D/R: 100%
• EXP: -15%
• SW: A
• END POINT
• THR: 100/125
• all the rest: 100/100
• SUB-TRIM
• AIL: -22
• ELE: +6
• PIT: -12
• all the rest: 0
• REVERSE
• Reversed: AIL, ELE & THR
• Normal: RUD, GYR, PIT, AU1, AU2
• TRIM: all zero
• THR-CUT: inhibit
• SWASH-AFR
• RATE-AIL: -47%
• RATE-ELE: +47%
• RATE-PIT: +30%
• F/S
• AIL: F/S +9%
• ELE: F/S +3%
• THR: F/S +17%
• RUD: F/S 0%
• GYR: F/S -25%
• PIT: F/S -7%
• AU1: NOR
• AU2: NOR
• AUX-CH
• CH5: NULL
• CH7: NULL
• CH8: NULL
• CH9: Sw-D, NORM
• PARAMETER
• TYPE: HELI(SR-3)
• MODUL: PCM
• ATL: ON
• TIMER: 6 minutes, STk-THR 7%
• Curves
• THR-CURVE
• NORM: 0% 55.5% 55.5% 55.5% 55.5% (2000rpm)
• IDL1: 70% 70% 70% 70% 70%
• IDR2: 80% 80% 80% 80% 80%
• IDL3: 0% 25% 50% 75% 100%
• PIT-CURVE
• NORM: 40% 45% 50% 75% 100% (-2.5º -> +12º)
• IDL1,2, HOLD: 0% 25% 50% 75% 100% (-12º -> +12º)
• IDL3: 50% 50% 50% 50% 50% (0º)
• REVO MIX: Inhibit
• GYRO SENS
• MODE: GY
• UP: AVC 30%
• DOWN: NOR 30%
• SW: B
• THR-HOLD
• POSI: +17%

The partlist, mostly included in the Super Combo:

• The heli itself
• Length: 1160mm
• Hight: 340mm
• Rotor diameter: 1347mm
• Weight: 2.29kg without batteries
• Build manual (local copy)
• 600MX Brushless Motor
• KV = 510 rpm/V
• Input voltage: 11.1V – 50.4V (i.e. 5700~25700 rpm)
• 12 stator arms, 10 magnetic poles
• Continuous current: 75A, bursts 125A⋅5s
• Continuous power: 3.3kW, bursts 5.5kW⋅5s
• Phoenix Ice2 HV 80 ESC
• 80A continuous
• Governor built-in
• Logging built-in
• 3x Align DS610 servo on the swash
• Digital
• Torque: 9.6kg⋅cm at 4.8V, 12kg⋅cm at 6V
• Speed: 0.10s / 60º at 4.8V, 0.08s / 60º at 6V
• 1x Align DS650 servo for the rudder
• Digital
• Torque: 4kg⋅cm at 4.8V, 5kg⋅cm at 6V
• Speed: 0.06s / 60º at 4.8V, 0.05s / 60º at 6V
• Align RCE-B6X external BEC
• Input voltage: 2 cell LiPo (7.4V)
• Output voltage: 5.8V
• Max current: 6A
• LED voltage monitor built-in
• Linear regulator
• I kept my R319DPS receiver from my Raptor
• 35MHz band, synthesized
• 1024PCM receiver, 8 proportional channels, 1 digital channel
• Align 3GX flybarless system
• Input voltage: 3.5V ~ 8.4V
• Current consumption: <80mA at 4.8V
• Gyro range: ±300º/sec swash, ±600º/sec rudder, 12bit resolution
• Software included on 8cm CD, which I was unable to read in my slot-loading drive; but also downloadable.
• I immediately upgraded the firmware to v1.2 (local copy)

Build notes

• Page 5: The main head was pre-assembled, but wasn’t tightened. Make sure you check all bolts and loctite them in place. I also added a generous amount of grease to the thrust bearings.
• Page 7: I waited to mount the motor onto its mount until I figured out where I wanted to put the ESC and the 10AWG cables.
• Page 7: Although the drawing is correct, it wasn’t clear to me that the bottom “Main shaft block” had to be mounted upside down compared to the top one. I only noticed that by page 16 when I kept having slop in the main shaft, even with both “main shaft spacers” inserted.
• Page 13: The tail head was also pre-assembled, and since I was unable to loosen the screws by hand, they seem to be tightened (maybe even a little too well)
• Page 17: Fitting in all the electronics into the tight cockpit isn’t as easy as the manual makes you believe…

The provided software only supports the bare minimum, both in functionality and user interface:

It’s Windows only, there is no zooming functionality and no exact value readout. The file format for the “Log file” is some obscure binary format. In short, inadequate.

The hardware

The provided communications hardware is decent. It’s a small ~1*3cm PCB with a female mini-USB connector on one side and a pigtail leading to a female Futaba J-type connector on the other side, which plugs into the charger.

This board is actually just an USB-to-Serial convertor by SiLabs. SiLabs provides drivers for Windows, Mac (local copy) & Linux
(local copy).

The protocol

The protocol seems to be fairly simple. Just connecting the charger to PC already produces a stream of bytes. There is no need for the computer to send any requests. I use a simple perl script that opens the serial port in the correct mode and produces the read bytes on STDOUT. The bytestream consists of 74 byte long messages wrapped in curly braces (`{` (0x7b) and `}` (0x7d)).

7B 9E 84 84  D0 85 80 EE  81 81 81 80  81 94 8A 80
81 96 82 8A  82 8E 86 81  81 80 8A 80  8A 80 8C B2
80 82 95 87  CC 80 80 80  80 8D CF 80  BA 83 D8 83
D6 80 80 80  80 80 80 80  80 80 80 80  80 80 80 80
80 80 80 80  80 80 81 8F  A4 38 30 7D

The last two bytes each contain 4 bits of the 8-bit checksum of the first 72 bytes:

(0x9e + 0x84 + … + 0x8f + 0xa4) % 0x100 = 0x80 -> 0x38 0x30

The 72 data-bytes all have their high 0×80 bit set, it only contains 7 bits of data. For the rest of this discussion, I’m only referring to the lower 7 bits of each byte. Here are the data-pieces that I discovered. Byte numbers start at 0 for the first data byte (i.e. 0x9e).

• Byte 7 contains part of the state
• bit 0×01 is set when charging, clear when discharging
• bit 0×10 is set when cycling, clear when single charging or discharging
• Byte 8 contains the set NiCd charge current in dA
• Byte 9 contains the set NiCd discharge current in dA
• Byte 12 contains the set NiMH charge current in dA
• Byte 13 contains the set NiMH discharge current in dA
• Byte 14, bit 0×01 contains the cycle mode, set for {Charge,Discharge}, clear for {Discharge,Charge}
• Byte 15 contains the cycle count
• Byte 16 contains the set Li__ charge current in dA
• Byte 17 contains the set Li__ charge cell count
• Byte 18 contains the set Li__ discharge current in dA
• Byte 19 contains the set Li__ discharge cell count
• Byte 20 contains the set Pb charge current in dA
• Byte 21 contains the set Pb cell count
• Byte 22 contains the mode:
• 0×80: Config
• 0×81: Li
• 0×82: NiMH
• 0×83: NiCd
• 0×84: Pb
• 0×85: Save
• 0×86: Load
• Byte 23 contains the running state: bit 0×01 is set when running, cleared when standby
• Byte 24 & 25 contain the set NiMH discharge voltage in daV and cV
• Byte 26 & 27 contains the set NiCd discharge voltage in daV and cV
• Byte 32 & 33 contain the actual current in A and cA
• Byte 34 & 35 contain the catual voltage in V and cV
• Byte 40 & 41 contain the input voltage in V and cV
• Byte 42 & 43 contain the charge in dAh and mAh
• Bytes 44 & 45; 46 & 47; 48 & 49; 50 & 51; 52 & 53; 54 & 55 contain the individual Li__ cell voltages in V and cV
• Byte 69 contains the time in minutes

Or if you’re lazy, just feed in the bytes into this perl script.

The specs

The charger is run from DC power. It accepts 11-15V DC, so it’s designed to run of a car battery or an equivalent power supply. Make sure your power supply can provide enough power! I used an 28A 13.8V switched-mode power supply.

The box contains 4 independent chargers, with only their input connected together. In fact, they are so independent, that they even crash independent:

Each of the 4 chargers can charge:

• Lithium-based batteries (Lithium-ion, Lithium Polymer and the newer Lithium Iron Phosphate), up to 6 cells in series (22.2V) with built-in balancer
• Nickel-based batteries (NiMH and NiCd), up to 15 cells (18V)
• Lead-Acid batteries, up to 10 cells (20V)

It supports charging at up to 5A or 50W (whichever limit is reached first) per charger, which isn’t particularly fast. However, this isn’t particularly important when charging Lithium-based batteries. These require a CC-CV charging process: batteries are charged with a constant current (CC-phase) until they reach 4.2V/cell. After that, the charger switches to constant voltage (CV-phase) and maintains that 4.2V/cell by decreasing the charge current. When the charge current reaches 0 (or practically, 2% of the original charge current), the battery is considered full. This means that the CV-phase will always take the same amount of time, independent of the charge current during the CC-phase. This graph suggests that the CV-phase takes ~24 minutes.

The hardware interface

The input side consists of two 4mm “banana” bullet connectors which plug right in to most power supplies. They also provide clamps, so you can clamp on to a car battery.

The side of the batteries has 4 pairs of 4mm sockets. The included accessories include conversions to crocodile clips, male Tamiya connector, female Futaba connector and female JST/BEC connector.

The balance connections are unkeyed and spaced 2.54mm (0.1″) apart, so you can plug JST-XH connectors straight into the charger. The box also provided a board that receive 2S-6S FP/TP, and a second board that receives 2S-6S JST-XH.

The computer interface

The charger also supports a computer interface. To be honest, it was a bit of a disappointment. For one I expected to be able to get detailed voltage/current from all 4 chargers simultaneously. Turns out that not only I’m limited to one charger at a time, only charger 1 and 2 have the needed output port to connect too! Also, the software was provided on an 8cm CD-ROM, which I can’t read in my slot-loading drive! More on this in my next post.

This is a great helicopter for beginners. Its setup is very gentle and it can take some gusty winds. The governor allows you to concentrate on flying before having to fine-tune the engine. It’s also fast to refuel (in contrast with recharging a LiPo battery).

I’m selling it because my new club does not allow nitro.

I’m selling, preferably as a whole:

• The helicopter itself, including manual
• All servos (3x Futaba 3152, 1x 9206, 1x 9254)
• OS 50SX-H Hyper motor (incl manual)
• Gy401 tail gyro (incl manual)
• GV-1 governor (incl manual)
• Rx battery 3600mAh 4.8V, not new but still usable
• battery-monitor: shows the charge-state of the Rx battery
• NO receiver
• fuelpump
• Starter engine & pin
• 4 liters of fuel
• glow heater

In summary: everything you need to fly expect the transmitter, the receiver & a battery charger

I prefer you come and pick it up near Brussels, Belgium; that way I can show you it still flies.

If you are interested, feel free to propose a price.