Hi all,

I have try to use the joystick to control  my APM 1.4 (2.28)  the joystick work fine in simulation in Xplane but if i try to use on real i have several Issue :

1) the joystick center is not the same of the 0 radio center so when the joystick is enable the the varius command are not to 0 (center ) .

2) when I use the joystick the servo movment is less sensitive than the radio  the radio I use is a PCM with 1024 )

I have calibrated the radio, than with the radio off i have calibrated the joystick previus in windows and then in APM Planner .

when i turn on the radio the joystick loose is initial setting .

were i mistake  ?

best regards


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the joystick uses the trim value you had during calibration, so i would asume that is wrong.

How would I set up a control of a pan and tilt camera with a USB game joystick. My plan is to use servo put 5 and 6 on the APM 1.0 to control the pan and tilt. I don't want the pan and tilt to use the RC receiver. Any help with this would be great. Michael Oborne.

Hi  Michael,
Tanks for the answer, so i have to calibrate joystick with the radio trasmitter ON ?
Is possible that the use of exponential, dual rate,  and subtrim  on the radio generate some issues on the calibration of joystick in the APM .

I have planned in future to fly without the RC  radio and then i have in mind to use only the joystick  and as telecomunication system a three way system composed by 2,4 ghz (xbee), GSM/HSPA Modem, and Satellite module (the system with the best signal is the system active and the other system are in Hot Standby)  so an rc reciver in my future development are not needed, in this case is possibile to setup the joystick or i need to modify the code of APM ?.

Best Regards

Alessandro Vitali

Tanks Michael Now thw joystick calibration is Ok .

I have seen that  there are some glitch in the servo movemen when i use the joystick,   mav link protocol loss a lot packet  so i think that this is the reason of this glitch. 

another problem is that the movemet of the servo are not linear and fluid as when i use the rc trasmitter control.

do you have any idea how I can Fix  this problem ?

Alessandro, have a look at the solution from this discussion(Page11):


The problem we discovered was the fact that the Xbee and APC220 are all single duplex communication, meaning that you can only either transmit or received, but not simultaneously.  The result is that mavlink packets from the APM are starving out the packets sent from the PC to the APM.  The solution was to set up a link where two pairs of modems are used, one for transmit, and one for receive.  Not an idea solution, unless a cheap full duplex wireless modem can be found.

Tanks Ellison,

I haven't see this discussion, when i have read, now  the problem is clear.

The solutiuon that you have find is perfect .

I have think to buy a cisco Aironet access ponit (the older version are cheap)  and try  to  disassembly to see the modem  vendor and serial number and then try to search in the internet, then if i found the modem we can try to change the xbee module.

I don't think you understand, a Cisco Aironet is also not Full Duplex by default. You must use two different paired radio paths one for uplink and one for downlink. The only reliable way is 4 separate modems or some really expensive set of modems that internally really is two modems per end. Further, for range, they probably need to be separate radio bands 900 mhz and 2.4 Ghz. Or if talking a Wifi, one pair is on channel 1 and the other pair is on channel 11. This why true full duplex always has two separate carrier fequencies, one for uplink and the other for downlink. I know Aironets are advanced and can run separate channels, but I really doubt that is the correct solution or easy solution. Two modems on the same band still can interfere and cause packet loss when true asyncronous coms is required. Further, without some serious integration into the code, I don't know how you would even begin to set up a dual link pair via ethernet when mission planner expects a serial port. I also don't know how to set this up in Aironet and I have extensive training on them. You can't just pull the wireless module out of a Cisco, either, how would you set up the communications channel. That's all done via code commands to the modules and is violatile. So you would have to reverse engineer the firmware, rewrite for permanent settings, provide some sort of serial translation and pray the whole thing meets your range requirements. I think 4 xbees beats that cost and time wise hands down.

Don't over think things Vernon.  The solution I have outline uses APC220 running different frequencies, but will work with the same frequency as well.  You can set a different network address for the rx and tx side.  The problem is not interference or lack of bandwith.  It's the fact that using one half duplex modem means the modem will either let you transmit or receive, but not both at the same time.  By splitting the rx and tx onto two modems that problem is solved.

True and I understood it's unlikely the APM code is configured to transmit async (time slot wise). I was agreeing, using two modems by far seemed the simplest solution. My real concern was the discussion of using wireless access point modules to rig up basically the same thing. Unless somebody had a project and did this already, I couldn't even imagine going down that path as a viable option.


That said, maybe modules like this

http://www.serialio.com/products/mobile/wifi/WiSnapKit1.php which are a WIFI to serial conversion supporting up to 2.7Mbps would eliminate the congestion. They claim the range is up to 1000feet with the off chip antenna. Set the data rate up just like xbees, and see what it does.

The GCS uplink/downlink messages are done by the APM in the 50hz loop.  From my tests it seems to be sufficient for drone control, at this point.  Introducing asynchronous communication into the picture will cause other issues, like ordering and loss of packets.  This is exactly what would happen if you use WiFi as your link layer.

Vernon,  I am not an expert of  layer 2 wirless comunication but i know what  is a full and half duplex comunication . I have te CCNP and CCIP cisco certification, i know that the wireless modem work in half duplex but  if i rememeber well the protocol used in wirless lan use a TDM and CSMA/CA and other technique to solve the problem  of packet collision, yes the band is shared between all modem device in the network, but i think that this implementation of the protocol are written in the firmware of the modem . so if we can  use the same technique to avoid packet collision (bad crc) and if we can have a little bit more bandwitdth to allow the comunication between two host is not a problem a half duplex comunication.

I did not know if is a good idea or not the only method to know that i  i have is to try to do


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