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Posted by JW57RC | Aug 19, 2015 @ 08:10 AM | 1,528 Views
I have a CX20 FC that would not flash the Green GPS indicator LED. I searched this thread (and others) for the circuit diagram. I never found one, so I traced the circuit. Here's what I came up with.

This is a common anode circuit and all the LEDs are connected to a common Vcc. It appears that the FC just brings the appropriate cathode to ground to light the LED. The green LED (black) is connected to the Mega2560 PA3 pin, the yellow LED (white) is connected to PA4 and the red (red) is connected to PA5. These pins are also used by the internal blue, yellow and red LEDs.

I have since replaced that FC because I could not ever get telemetry to function.

Please let me know if you find any conflicting details.
Posted by JW57RC | Aug 16, 2015 @ 04:19 PM | 1,343 Views
I've seen a few Arduino-based devices to extend the number of potentiometers and switches for PPM-based TX, the earliest I found by Ian Johnston in 2010. I set my extra switches into a box that attaches to the back of the Devo7e running DeviationTX software. My box provides 2 potentiometers and three 3-way switches through the magic of the Arduino Pro Mini. The box is powered by a single switched 9V battery (with indicator LED) and connects to the Devo7e DSC port.

The advantage to this approach is that this box can be used with ANY TX that has a DSC in jack. However my main motivation is the ability to easily open up the box and add or change the functionality. My first modification will be to remove an existing thumbwheel (Analog port 3) and use a 6-position rotary switch instead.

This box includes:
Arduino Pro Mini ATMega328P 5v/16Mhz (eBay) - note I used the one without the USB port because I already have an FTDI USB-to-serial board
1 x Hammond 1591BSBK project box (112mm x 62mm x 27mm) (Amazon)
2 x 5k Linear Potentiometer (eBay)
3 x On-off-on switch (Radio Shack 275-325)
1 x 3.5mm 2-conductor phono jack (274-248)
1 x micro On-off switch (275-524)
1 x 3mm yellow LED
1 x 390ohm 1/4watt resistor
1 x 9v battery connector
1 x 3.5mm 150mm phono cable

The hookups can be soldered pretty quickly. I used a 90 degree pin and AMP connectors since I like to tinker. While it takes up more space, I can easily move switches or attach my programmer to the board.
Posted by JW57RC | Jul 25, 2015 @ 09:39 PM | 1,938 Views
The CX20 Flight Controller is sold as Open Source, but the actual source is not really very open. Many on the CX20 "Big" thread have seen issues with support of telemetry and power monitors, and in May, 2015 I received a version of the board with connectors for which we still don't have any information.

In a nutshell, it appears that the only CX20 Flight Controller for which Telemetry and Power Monitor are supported -- and only if you use "Custom" firmware -- is the 252_v5.0 revision. You can solder directly to some extremely tiny points on the other revisions and use standard or custom firmware, but I think few of us have the skills or equipment needed to do this without disastrous results!

I'd like to thank @skywarka, @dkemxr, @Bob_AZ and others for their work detailing the firmware versions that support telemetry.

I've compiled a list of the known FC boards based on the photos in the thread and my own experience with three boards (1 each v2.0, v5.0 and the new, unmarked version). It is entirely possible that my own experiences were unsuccessful due to hardware failures (perhaps caused by my own poking about!), so I would love to hear from anyone who can tell me that their FC works under these circumstances!

I've shared this table in Google Docs at

APM FC		Compass	UART	ADC	IO Board	Firmware		FW			Telemetry
Version		Connect	Connect	Connect	Ver.	Ver.		Source		 	available?
252_		No
...Continue Reading
Posted by JW57RC | Jun 17, 2015 @ 01:04 PM | 1,621 Views
I wanted a better way to tell the orientation of my CX-20 from a distance, and I have seen high-power LED headlights for these quads. I wasn't happy with the look or functions of commercial LEDs, so I designed and installed my own LED array.
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Description: CX-20 Headlight LED Array in action.  I couldn't take the photo straight on because the lights overwhelmed my camera exposure.Name: IMG_0683.jpg
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Description: The 10mm LED is REALLY bright (28k mcd) and focused (10 degrees).  The other two are 7k mcd and more generally visible.

This modification drills three holes into the lower shell of the CX-20 to attach high-power LEDs. I've connected them to the Flight Controller (FC) 5v and ground rail. This LED array draws about 80mA of current, not insignificant, but manageable.

5mm High Intensity White LED RadioShack 276-0017 (2 pieces)
10mm High Intensity White LED RadioShack 276-0005
5mm snap-in LED Holders RadioShack 276-0079
1x 82 ohm resistor (1/8 or 1/4 watt ok)
2x 68 ohm resistor (1/8 or 1/4 watt ok)
2x JST single connector for 2.54mm pin header - I used pre-terminated from a reel from Banggood, SKU067911
connecting wire, shrink tube and other solder supplies
...Continue Reading
Posted by JW57RC | May 26, 2015 @ 08:37 PM | 2,503 Views
I took the challenge and got my DVM to try to figure out the connections on the new Flight Controller. Here are my findings so far; I would welcome any comments, corrections or contributions!

This new controller has four IO connectors in addition to the normal motor and RX connections. Telemetry and Compass connections have been documented before so I focused on the remaining two connectors. At this point I think I have a lot of raw material, but I am stumped as to what these are used for. The new FC I/O board layout is a substantial update from previous versions, as I mentioned, with 4 connectors instead of the previous 2 (see figure 1.) There appear to be a number of changes on the top of the CPU board, but the main processors are still the ATMega 2560 and ATMega 32U. I noticed that the ATMega 2560 chip APM pins (pins 84/85) are connected to something, but I don't have the equipment or experience to figure out where they go on this (at least) three-layer board. Maybe someone who knows chips can determine any new functionality or capacity.

In addition to the increased number of I/O connectors, the most notable difference is that the interconnect between the two boards. These pin/socket connections are now set up with 2 sets of 22 connections (44 circuits), rather than the previous 2 sets of 16 (32) connections. Many of the new connections appear to be duplicate lines for the 4 primary RX input (AETR) and the four motors. I've laid out the connections in figure 2. I...Continue Reading
Posted by JW57RC | Nov 17, 2014 @ 01:37 PM | 2,871 Views
The full-size transmitter that comes with the WLToys V912 RTF helicopter is generally regarded as a good transmitter for learning, especially when you consider the cost. But it lacks two features that I could not live without:
- Throttle Hold: for safety I want to have the throttle at the lowest setting any time that I am not actively flying. The is a standard feature on most mid- to high-end radios. I particularly want this feature when working with kids!
- Turbo Rate Switch: now that I have the skill to fly this heli, I always use the highest available servo rates. The TX has a Turbo-mode momentary switch on the right shoulder, and I want that on all the time so I have to push it in, but my hands don't work like that!
This mod is shown on a Mode 2 TX; be sure to select the correct gimbal potentiometer if you are not using Mode 2.

Turbo Mode Switch:
Radio Shack pn 275-0009, Illuminated Pushbutton Switch
The Turbo Mode switch mod is well documented in the V912 discussions. The only thing I did differently wasto use a lighted push-button on-off switch. Since I use this TX with other models, the light helps me to remember that I need to verify that switch setting before binding to my other models (in the case of the V911 it makes the tail go all wrong!).

To light the internal LED, I tapped into the LED lighting from the existing V on the front of the TX. You can see the Red and Blue wires I used in the images. I also used the existing white wires for the switched...Continue Reading