This s my first setup with apm2 and 3dr 900 MHz radios.

I am in the testing and setup phase and the radio link disconnects randomly every 2-6 min. Some times the green lights starts blinking indicating the radio link is lost, most of the timeout stays green (or reconnects fast enough so I do not see it blinking) . Once green again I need to "re"connect via APM planner.

2nd challenge is that I have connectivity via com15 through the mission planner but when I go to the setup page (in APM mission planner) for the 3dr radios, and click on download settings I get an error message that the com port is incorrect.

Thanks for your help,

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Hi Matthias,

It shouldn't lose the link easily. What parameters do you have set?

If you use a terminal, try AT&T=RSSI and look at what is happening with the signal and noise levels. You could also do AT&T=TDM if you want to see low level debug information on the TDM synchronisation.

Cheers, Tridge

My Terminal Output Looks like this ( see below)  the command do not appear to be accepted

I am using Putty

BTW the my win 7 ultimate did not recognize the modem/ radio So I installed the FT232R Drivers

The mission Planner was receiving data after that but It behaves different from using a USB Cable.

I do not seem to be able to send commands to the APM with the radios.

Hmmmm ....If I go to the Setup screen for the 3DR radio and click on "Load Settings"  the local radio reports Rev 1.5 the Remote is at  1.3  Is that normal ?

   KUy*øÃU%z O'C F<(ÝU{>ÀƸR½®U|I(þèU}%ZÛ
                                         ¬U~#ê[ÛÛÛÛê&UO3X½Û-<ȯ!?(6»r£»½z;;ÂÎ;(<­<ÓÐ5:ºUËU»½tj;;Çë;(2Ê<àï;Qê\ÛÛÛÛ¡U Tc̽yÂ<Ç6«?;¾H¢ºv¦ºA¦-»UJ@ƸRÜeU
          "ú'`è(~UxU~U*³`U% YÈC F<k±U>ÀƸRÈI(ËU%ZÛÌþU#ê\ÛÛÚÛ(
                                                             U YD½ÅÚ<È>Ò?"7»MU£»½P;;Ý,;(^Ù<Ò $;¹ôkÂýU7UïU
                         ",'`è)UxÄU*:]U% ^¸@C  F<ä/U >ÀÃ×
                                                         fU¡I(_EU¢%ZÛ\U£#ê\ÛÛÚÛáSU ¤^Ľì<ÉÈ»


OK so I reread the documentation and some other posts. and I conclude that both radios need to be at the same rev level.

I received an unmatched pair.of Radios :( and in order to fix that I need an "FTDI" cable.

(Or I could make my own can make my own Serial Cable).

Will This cable work:

Or Can You recommend a  better cable?

To Clarify assuming you have a matched pair, The upgrade option in the mission planner does not help until ONE HAS A FTDI CABLE that will allow the upgrade of the remote radio as well.?!?
Or can you Upgrade over the air if the radios talk properly?

2nd Challenge

I can issue AT commands to the Radio all day long but I am not getting an answer. ( echo)

Its' been quite a while that I messed with At commands but ATE1 I believe should turn on echo mode.

I am getting absolutely nothing back from the radio.

Thanks for you help...


   I think any 3.3v or 5v TTL serial cable will work.  I'm using a 3.3v cable and only have 5v, gnd, tx, and rx connceted (no CTS or RTS).  Everything works fine for me when I plug one radio into each side of my laptop.  I open 2 putty windows, one on each com port.  I have no problem typing back and forth between them.

   To enter command mode you have to enter "+++", which should give you "OK" after a sec.  These radios don't implement a full AT command set, it's just the style the command interface was written like.  If you want echo on then just turn it on in your terminal program.  You shouldn't be getting anything "back" from your radio except responses to AT commands after you've entered command mode with "+++".

+++ that will be helpful l!  Thanks! I'll try that when I get home ...

TTL cable was ordered yesterday from Sparkfun I assume once I have the radios on the same rev my issues will go away.

Thanks you for everybody's help.

I'll keep you posted!


Update - no success :(
FTDI cable from Sparkfun arrived yesterday.

Double checked pins and connected to my laptop.

The Modem fired up and the APM planned saw it as  a local radio wit the old 1.3 software.

I pressed the upload firmware button. It connected erased the firmware and ended with

"Update Failed SYNC LOST"  

Fail: lost Synchronization with Boot loader.

The red LED stays on indicating boot loader mode.

I tried 9600 baud as well as the 57600 with the same results.

Suggestion welcome


do you have test to define 57600 on the :

- windows driver of serial interface

- and on arduplaner ?

for me it's solve the problem

Fred ,

Thanks for your answer. I have the com port  set to 57600 8N1N (as well as the Ardu Planner ( which I believe may be irrelevant for a software upload)

At this I am looking for some instructions on how to "manually" talk to the boot loader and get the new firmware uploaded.

Or figure out why I have a communication mismatch...

Can anybody help me please?

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