Re: [Paparazzi-devel] 3dr as modem datalink

[Chris Gough]

On 07/02/2014, at 10:06 PM, evan igor <address@hidden> wrote:

Hi ,

sorry but what is the meaning of  dissable the mavlink protocol data send trough the mission planner

The SiK firmware can be configured with AT serial commands. AT setting 6 switches on/off MavLink mode. You can ask the modem what the AT 6 setting is with the command "AT6?". It will answer 0 (transparent serial, MavLink mode OFF) or 1 (MavLink mode ON).

With MavLink mode on, the modem will do 2 things differently. First, it will organise data into radio packets so there is a whole number of MavLink frames in each radio packet (no frames split across packets). This is good because it minimizes the cost of dropped packets. The result is better bandwidth and range in noisy conditions. The other thing it does is inject link quality (RSSI and other statistics) data for the modems info the data stream, which is interesting to know.

as i connected it with paparazzi lisa/m and make the modem react as transparent but no link with CGS.

If you are not sending MavLink data, the MavLink framing is not helpful, and the Mavlink injection won't happen. I don't know if you will get a dead link like you described, I think it's undefined.

You can switch the MavLink mode off with the command "ATS6=0", then persist the change with "AT&W". The command to switch it on is "ATS6=1", but don't do that.

In case you are interested, see here for details on how frames are packed in MavLink mode:

https://github.com/tridge/SiK/blob/master/Firmware/radio/packet.c

See here for how RSSI packets are injected:

https://github.com/tridge/SiK/blob/master/Firmware/radio/mavlink.c

It would be possible to create a Paparazzi framing mode, but nobody's done that. I spoke to Tridge about it a while ago and he said "patches welcome". ATS6=2 anyone?

Chris Gough

thanks 

On Mon, Jan 20, 2014 at 11:49 PM, Chris Gough <address@hidden> wrote:

The 3dr radio is an example of SIK firmware modem. There are others, not just 3rd 'clones'. Early 433mhz USB 3dr modems has a bad interference problem on USB2/3, they were very cheap on stock-dumping sites for a while. 433mhz UART modules are fine, it was only the one with the onboard USB adapter that was the problem. Later models are probably OK I guess.

http://wiki.paparazziuav.org/wiki/Modems#SiLabs_Si1000_SoC_based_modems

Like Dave says, they don't mesh (point to point only) and they don't have encryption. They do have discrete channels, so accidental collisions are not a big deal.

Not sure what 'fault  tolerance' means exactly. They are both packet radios with acknowledgment and checksums, so dropped/garbled packets are resent.

Basically, they both work fine in typical usage scenarios (one uav, one GCS). You need to configure them right of course, see details on the wiki.

Chris Gough

On 20/01/2014, at 12:34 PM, onefastdaddy <address@hidden> wrote:

Hello,

3DR one I have not used. No need to. The XBee works great every time which for me makes it the best.

The XBee is a common parts you can buy around the globe. It will do mesh networking allowing one ground module to act as the coordinator and the aircraft ones to be routers that route the messages to each other.

I do not believe the 3DR radio has encryption. Meaning if you want some guy next door to have the same module and send your drone commands that's ok I suppose. Not sure about fault tolerance etc. It appears to be based on a generic chipset. I see so many different versions on Alibaba and eBay for less than 20 dollars.

Lisa/S maybe using the same chips but they have added extra features that make it attractive and it has a smaller form factor. Here's a link to the 1bit site (http://1bitsquared.com/products/superbit-cyrf-module) I'd recommend that one if you really just do not like XBee for some reason.

-David

On 01/19/2014 11:18 AM, evan igor wrote:

Hi,

anybody try 3dr radio modem as data link tell me what is the difference for the airframe between 3dr and xbee as example and which better?

thanks

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