Tag Archives: FrSky

How to repair broken 2.4Ghz antenna

Posted by on December 27, 2014 No comments

I crashed my SG Adventure FPV quad last week and broke the two antennas of my FrSky D4R-II receiver. As I don’t wanted to wait for a new receiver, I decided to repair the one  (the connector of the second one was totally destroyed so it couldn’t be repaired).

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The size of the broken 2.4Ghz was about half the size of the original one after the crash. There are two possibilities in general: buy new one and replace it by removing the old one from the receiver connector or cut the broken antenna, so its length is appropriate to the wave length.

The wavelength by 2.4Ghz is 0,125 meters (125mm). The antenna should be 1/4 of the wavelength. In the FrSky receivers it is a bit more. So I just needed to cut the rest of my antenna to 31,25mm. By cutting I mean firstly to remove 31,25mm of the plastic/PVC. The next layer is the shielding. Remove this one too to the length of 31,25mm. By doing this the last 31,25mm should be the dielectric and the wire in it, that is the “active” antenna. That’s it. Now the antenna is functional again.

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Note that there is a discussion if only the last unshielded 31,25mm are important or the length of the shielded part too. Didn’t find an answer on that question (even in the rc-groups thread about that).

FrSky CPPM firmware update with Arduino

Posted by on June 1, 2014 17 comments

I have an FrSky D8R-II Plus receiver on my “SG Adventure” quad. I read on the DIY Drones site, that it is possible to update this receiver with the firmware for the FrSky D8R-XP, so I could use with CPPM signal. With CPPM you only use one wire for all the channels and not separate wires for every channel.

You can easily buy this FrSky Update Cable or you can save a bit money and time by updating/flashing the receiver with Arduino, which has an FTDI chip on board. I have an Arduino Uno, but my revision of the board doesn’t have an FTDI chip. So I decided to simply use my actual flight controller – the Multiwii Megapirate AIO board. You can use any Arduino based board with FTDI chip.

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First you need to download the 27ms CPPM firmware from the FrSky website. This firmware is actually for the D8R-XP receiver as mentioned, but it works with the D8R-II Plus too. Please keep in mind, that is officially not supported for the D8R-II Plus and I am not responsible for any damages on your hardware by doing this too. If you agree keep reading 🙂

Download the official FTDI Prog.  – EEPROM Programming Utility and install it on your computer.

There is a jumper on the side of your receiver. Take it out and place the jumper on the signal pins for channel 7 and 8, so these are bridged. This will then take the receiver into update mode.

Then connect the TX, RX and GND pins from your Arduino board to the TX, RX and GND pins on the side of your D8R-II Plus receiver. Important: Do not reverse the TX and RX as usual by Arduino. Connect TX to TX and RX to RX. To power your receiver: you can use a 5V battery or connect it as usual to the flight controller.

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To use the Arduino board for this we only need the FTDI chip, so we will suppress the Atmega chip by a constant press on the reset button. After the reset button is pressed, connect your board to the USB port of your computer. It could possibly install some drivers, so give it some time. Keep pressing the reset button 🙂

Open the FTDI Prog. Scan for FTDI Devices. Then invert the TX and RX as shown on the screenshots below and click on the flash icon. In the new opened window click “Program”. (Tipp: Remember to undone this procedure after flashing your receiver.)

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Keep pressing the reset button 🙂 Now go to the folder, where you downloaded the firmware file from the FrSky website, extract it and start the .exe file.

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Chose the right COM port in the dropdown menu, chose the firmware file from the same folder by clicking on “File”. If everything is fine, you should see the UID number in the bottom of window. If so, just click “Download” to upload the firmware. (For more info about these last steps, there is a pdf-manual in the folder, where the .exe file is. At the end you should have a working CPPM FrSky D8R-II Plus receiver. Now you can release the reset button of your Arduino or Multiwii Megapirate AIO board. I hope I have helped you, save some time and money with this method.

p.s. To use your receiver in CPPM mode after flashing, place the jumper on signal pins CH3 and CH4, so these are bridged. The CPPM signal will be on CH1 pin.

Update 12.08.2014: I updated the same way my new FrSky D4R-II receiver. It is smaller than the D8R-II Plus, weights only 5 gram and with the CPPM 27ms firmware has 8 Channels and the exact same functionality as the D8R-II Plus. Check how my SG Adventure carbon frame look now with the Pixhawk and the D4R-II receiver here.