RF Module Soft Power Switch for AR9x, Skyboard, 9XR-PRO

[jhsa]

As you know, the Skyboard, Ar9x board, as well as the 9XR-PRO can have a second module plugged to the PPM2 pin, and installed internally. The thing is that they don't provide firmware controlled power to the module. That means, if you install a second module inside the radio, it will always be ON, unless you install some kind of switch.
A while ago I had one of those rare moments when a light bulb hover above my head and I thought that maybe it would be possible to control the power to any RF module depending on if there was a PPM/serial signal at the RF module's input.

I asked for help on the arduino forums, and a user did write the code for an arduino. So it would be possible to also use an arduino or even an Attiny85/45 chip, which is much smaller
Here is the link to the forum:

http://forum.arduino.cc/index.php?topic ... msg2605062

Obviously all this is only possible because Mike added an "OFF" option to the PPM1 and PPM2 settings in the "Protocol" Menu. we can now just turn the signal OFF and consequently also turn the RF power OFF for the corresponding Module. No need to use CPU pins that can be very useful for other stuff like more switches..

Mike, thank you very much for making this possible

Here is the schematic of the circuit I'm using on my Ar9x radio.

So, basically what this circuit does is to monitor the PPM1 and PPM2 signals. If a signal is detected on Pin2 or Pin3 of the ATtiny85 microprocessor, the corresponding output (Pin5 or Pin6) will be turned ON. The output pins will then control a couple MOSFET transistors that will act as power switches, and can then turn the internal and external RF modules ON or OFF depending on the settings in the protocol menu.
You will need to tap both PPM1 and 2 signals and connect them to the board.(Will make a diagram).
Then you need to tap the RF power line that comes from the power switch, isolate it from Pin3 of the module bay, and connect it to the board. Then connect the internal and external power outputs to the modules.. The external output connects to Pin3 of the module bay. As i said, i will try to make a diagram as this can be a bit confusing..

Inside the zip file attached below you can find the eagle files for making a PCB for this project.. I've used 0805 and 1206 SMD components. You could use only 0805 if you wish..
I'm sure someone can design a better PCB. Mine is working fine though. There are also a couple PDF files with the board design already mirrored.

You can see I also have put some programming pads on the PCB's. They make it easy to flash the Attiny85. Just connect the programmer to those pads.

The code provided in the zip file should be flashed using the Arduino IDE. I have also included an HEX file in case you use some other programmer, or don't want to use the arduino IDE.
I always have trouble burning the bootloader to the Attiny using the Arduino IDE. It always fails. Actually there is no bootloader. The IDE just programs the right fuses to the chip. But I have to use AVR Studio 4 to program the fuses. Perhaps there are other programs that can also do it, but I didn't try any other.
After changing the fuses I can program the Attiny with the arduino IDE using an UsbAsp programmer. I guess other supported programmers might also work, but I didn't try any other..

The fuses are:

Low - E2
High - DF
Extended - FF

On the Arduino IDE, you should select "Attiny85, 8Mhz internal clock" as the board..

As I said above, I have one of these boards installed in my Ar9x board for a couple months now, and never had a problem. it seems to be working very well. Will install one on my Skyboard radio, and try to do the same on my 9XR-PRO. It would be nice if the PRO had enough space inside the case for a DHT module. But I don't know if it is possible..

The wires on the left bottom part of the board are only for programming the Attiny chip. I just left them there in case the code changes..

Obviously, I take no responsibility for any failures or damage resulting from you building this project.. It really works nice for me, and it is a wonderful feature. I have been flying my quad a lot indoors with it, and now also my other models at the field. I am very happy with it.. Not a single glitch, and it is not expected

I did wait for quite a while before I release this project because I wanted to be sure that it works. I think that after a couple months without problems, is now time to share it with you..

Have fun and do not hesitate to ask any questions about the project..

João

[MikeB]

Have a look at the "Pin Change Interrupt" in the processor datasheet. You should be able to set a mask register to monitor a specific bit, then you read the PCIFR register to see if a change has happened, you don't actually need an interrupt. If a change has taken place, write a '1' to the relevant bit in the PCIFR to clear it (yes a'1' !). If 3 seconds passes without seeing the PCIFR register show a change, there was no signal.

Mike.

[jhsa]

Mike, I have no idea of what you're talking about.
I am googling it though. but i can't see myself solving this to be honest nothing to do with blinking a LED which I can do Interrupts are a bit (a lot) over my skills..

Thanks for your answer..

João

[MikeB]

Which pin are you wanting to monitor?
If you read what I said, you don't actually need to use an interrupt, just use a couple of hardware registers that will detect a change on the pin.
Have you got the datasheet of the M328?

Mike.

[jhsa]

The pin can be any suitable one.. I am planning to test all this on an arduino and then move it to an Attiny85 if possible.
I can download the datasheet. doing it right now.

João

[MikeB]

The tiny85 has the same "pin change interrupt" feature.
On the Pro Mini, suppose you want to monitor IO5. This is Port D bit 5, also called PCINT21.
PCINT21 is in the PCMSK2 register, bit 5, so set PCMSK2 to 0b00100000, 0x20, decimal 32.
Now, every time the is a change on IO5, the bit PCIF2 in the PCIFR register will be set.
Simply look at PCIF2 in PCIFR, and if it is set, the has been a change on IO5. Just write a '1' to PCIF2 (write 0x04 to PCIFR) when you see it set to clear it.
If you don't see it set for your timeout period, then there were no changes on the input.

Mike.

[deaconFlyer]

Take a look at http://twit.tv and for a program called "Know How" ... there have been a lot of Arduino LED projects there lately (including one on Christmas lights) and the code samples etc. are available for download. You also get a full video documentation.

https://twit.tv/shows/know-how

One of my favourites is: https://twit.tv/shows/know-how/episodes ... tart=false

Look right near the start ... you'll recognize the HK parts!

Now I always have an inexpensive voltage regulator inline between the Arduino and the LEDS.

[jhsa]

Thank you.. will look and save..

João

[jhsa]

Thread name edited, and an explanation of what I'm trying to achieve added to the first post..

João

[jhsa]

Ok, some progress.. Thank you to Mike that made this project possible by implementing an option in protocol to turn PPM and PPM2 OFF.
The video below shows the NE555 based switch controlling the power to my multiprotocol module depending on the Serial signal from the radio being ON or OFF. When the switch detects the tx is sending a signal to the RF module, it will turn its power ON. When we turn the signal OFF, the module will power OFF after about 3 seconds.
So the basic is working, but following an advice from Mike I am looking at another IC to do the job. The 74HC123, which is a Dual retriggable monostable multivibrator.. it will allow to control both modules with just one chip and a couple more components
The TX used in the video is my 9x with the Ar9x board..
João

https://www.youtube.com/watch?v=uYxBXNjxEBs

[jhsa]

UPDATE: I got something working. It will be installed on the radio tomorrow and tested. It seems to be working..
I will be able to control the power of the RF modules with my Ar9x radio, skyboard, and probably the 9XR-PRO as well.
No extra pins are used..
The wires soldered to the round pads are connected to the programmer. They will be removed for normal operation. The Attiny chip will need to be flashed only once.
João

[jhsa]

Installed and being tested with the Ar9x board

João

https://www.youtube.com/watch?v=UWvSCh3DTis

[jhsa]

Little update..
Built another board smaller than the first one, changed some resistor values so it will work with the 9XR-PRO radio when sending PPM or Serial signal in "OpenDrain" configuration.. Thanks to Mike for alerting me to this situation, and for his help..
It seems to be working well, and of course, it will need more testing.. Here is a picture from the current board installed on my Ar9x radio.. The wires on the left bottom part of the board are only for programming the Attiny chip. I just left them there in case the code changes..
More updates soon.

João

[jhsa]

Another little update to this project.

I have been testing my RF module soft power switch by flying my very small quad at home.. Today I took my Ar9x radio with the RF module switch installed to the field, and for the first time flew one of my models with it. All went well as expected. So, i'm getting very close to releasing all the information and files so you guys can also build it..
Next i will also install one in my Skyboard radio. I would like to build also one for my 9XR-PRO, but I am not sure if there is space inside the radio to install an internal RF module

João

[jhsa]

First post updated with all the files I used to build this project. This also includes the code, of course

João

[jhsa]

This is working extremely well on my Ar9x radio. not problems whatsoever. It is really nice to have 1 internal module installed in the radio, and also external modules, and be able to switch their power depending if the active module uses them or not.I'm really happy i built this.. Will try to make a version of it for my 9XR-PRO as well

João

[jhsa]

I will try to design a smaller PCB. maybe using smaller Mosfets as well

João

[edelsailor]

Hello jhsa,

In the seach for a resolution to my troubles with a 4 in 1module not working, I came upon this thread. Below, I pulled an quote from a comment that you started the thread with.
"As you know, the Skyboard, Ar9x board, as well as the 9XR-PRO can have a second module plugged to the PPM2 pin, and installed internally. The thing is that they don't provide firmware controlled power to the module. That means, if you install a second module inside the radio, it will always be ON, unless you install some kind of switch."

If you we would clarify for me the reference to ppm primarily speaking, "The thing is that they don't provide firmware controlled power to the module." My confusion is that the module does not work when it is in the JR bay.
In my thread started as '9xrPro and Deviation', both you and mikeb answered. Mike mentioned that there would be no need to use the rotary switch, because the board(new) has needed resisters in place. I have discovered that the board from banggood and the board I purchased through Amazon.com appear to be different. I purchased the board at Amazon.com because the seller was adamant that there were fakes on the market, and the ones he was selling were not.
Anyhow back to the conundrum. In the settings on the 9xr Pro, I have the model using the "multi" protocol. In the protocol menu ppm is PPM2. Now I am assuming, from this thread, that PPM1 would be at the JRbay. Is this so?

More info: right out of the box, the 9xr Pro was flashed to the latest firmware 219. The eepSky version is also the latest. The model is an unedited eepn of an HK450 found on the web. Attempts to make the radio talk to a Spectrum ar6110e have failed. The "multi" protocol is set to PPM2
PPM2 SartChan 1
PPM2 Channels 8CH
Module ON
Proto Multi RxNum 0
Protocol DSM2
Type DSM2
Autobind N Option 0
Power High
1rst Chan 1

When I attempted to use the bind within the 9xr Pro menu (at model), no bind would occur. Then I tried the bind button on the module (push bind, then power on) nothing. Then I tried the model bind within the 9xr Pro menu, with the rotary switch to/at position 6, nothing. Then I tried the bind button on module with the rotary switch to/at position 6, success. But, no stick movements producing servo actions. Interesting occurance though. When I turn the tx off, then back on, the servos go to the "neutral" positions. But when I do this with the rotary switch on the module back at position 0, this does not happen. And when the battery is disconnected from the heli, bind is lost.

Sevos have been tested, and are responding when connected to a wifi reciever, and talked to from an app on my phone.

The ultimate questions; is PPM1 at pin 1 in the JR bay? If this is irrelevant and ppm is at pin 1 in the JR bay, regardless of soft switch in the protocol menue being PPM2, why is the model not talking to the servos? Will I have to flash the module, seeing how there are no version numbers references to firmware?

Thank you for the help.

P.S the photo of the 4 in 1 module board is identical to mine. And it has referenced the four solder positions that pascallanger refers to in his Github repository.



"if a cluttered desk signifies a cluttered mind, what does an empty desk signify"? Albert Einstein






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[Kilrah]

You don't say whether you actually added those resistors, nor if your module simply powers up correctly or not (LEDs...)

[edelsailor]

The module powers (green light). When the rotary switch is on position 0, the bind light (red) is on, never blinking. When the rotary switch is on position 6, it is blinking.
It goes to steady on when bound in position 6, and only when binding with the physical bind button on the module.
Binding is confirmed by the receiver's bind light going from flashing to steady on, and the ESC/BEC light going from blinking red to steady green.
I have no means to test the receiver
..


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[edelsailor]

And I did not add any resistors.

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[MikeB]

Form the DIT MultiProtocol thread (http://www.rcgroups.com/forums/showthread.php?t=2165676):

Option settings for DSM2/DSMX

option=number of channels and frame rate:

0 : 4 channels @22ms
1 : 5 channels @22ms
2 : 6 channels @22ms
3 : 7 channels @22ms

4 : 4 channels @11ms

5 : 5 channels @11ms
6 : 6 channels @11ms
7 : 7 channels @11ms

8 : 8 channels @22ms

9 : 9 channels @22ms
10 : 10 channels @22ms
11 : 11 channels @22ms
12 : 12 channels @22ms

You need to set the Option value to match what your receiver needs.

Mike.

[jhsa]

And you need PPM1. The PPM2 option doesn't even have "Multi" as far as I know, so I am surprised you selected "Multi" on PPM2??
Also this thread is about something very different. It is about a device to control the power to different RF modules in the radio. So your problem is a bit OFF TOPIC here

João

[edelsailor]

Folks thanks for the answer(s).
Threads are most often found from web searching. My search queries brought me here. I should have presented my apologies beforehand. My direction has been corrected, and more clues have been offered.
Verry much in your debt,
Cheers.

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[mozgy]

I will try to design a smaller PCB. maybe using smaller Mosfets as well

João

Hello,

very interesting project, here's my take on smaller PCB, still untested (enroute oshpark), will update with progress.

ty all
--
Mozz

[jhsa]

Very nice.. I wonder if the power track to the Mosfets isn't a bit too thin? There is enough space to make it a bit thicker..

Also i see that you used 2 Fets (Q1 and Q2) at the input. Why? It works well only with the resistors. You're adding 2 more components to the circuit that aren't really needed

But your board design is excellent in my opinion.. What program did you use?
Thanks for sharing. Don't forget to say how it works for you

João

[mozgy]

Heya,

thanks for comments,
- per trace calc and oshpark specs for 1A trace 12mil should be enough, so I am using 16mil traces in upper area
- I consider two resistors in voltage divider setup a bit intrusive so I used n-channel mosfet as input (any small signal one will do)

Two more components on the PCB, yes, sounds 'complicated' but as I shopped for previous PCB project I have those mosfets in 100s
and I don't think few more cents will hurt BOM !
YMMV

I used freeware version of Eagle (latest cadsoft one).

--
Mozz

[jhsa]

Heya,

thanks for comments,
- per trace calc and oshpark specs for 1A trace 12mil should be enough, so I am using 16mil traces in upper area

I would calculate the trace for more than 1A though, specially if others might use your board. Their modules might take more current than yours

- I consider two resistors in voltage divider setup a bit intrusive so I used n-channel mosfet as input (any small signal one will do)

Ok, but not really necessary. I have this working on my radios for nearly a year and never had a problem.. Never failed, and I don't expect it to..

Have you tested it with your radio already??

João

[mozgy]

Heya,

Heya,

thanks for comments,
- per trace calc and oshpark specs for 1A trace 12mil should be enough, so I am using 16mil traces in upper area

I would calculate the trace for more than 1A though, specially if others might use your board. Their modules might take more current than yours

Good point, will recalculate, but then, isn't using over 1A for TX quite a bit in outofspec power output Watt zone ?
(please do correct me if I'm wrong)

- I consider two resistors in voltage divider setup a bit intrusive so I used n-channel mosfet as input (any small signal one will do)

Ok, but not really necessary. I have this working on my radios for nearly a year and never had a problem.. Never failed, and I don't expect it to..

Have you tested it with your radio already??

João

If you mean n-channel mosfets as input, yes I tested that in my version of nRF24 module (based on goebish project). As this particular circuit, no, haven't tried yet, will do as soon as PCBs arrive.
Don't get me wrong, I'm not complaining, I'm just tinkering and trying to improve things (not necessarily successful ). Thank you for the starting idea.

--
Mozz

[jhsa]

Did you think that the 470k resistors might be pulldown resistors on the Attiny85 inputs?? I wouldn't put them there if they weren't necessary, specially not with that big value But Im interested if your setup with the fets work.. If they don't it is very easy to just solder the resistors instead anyway.

João