[federicodl]

i can use it on my Revo?

http://www.banggood.com/it/Ublox-NEO-M8N-Flight-Controller-GPS-with-Protective-Shell-for-PIX-PX4-Pixhawk-p-1005394.html?rmmds=search
thanks

[Mateusz]

Yes I use that one, after changing connectors to JST-SH 1.0 with 4 pins.
http://www.ebay.com/itm/20-Sets-Mini-Micro-Sh-1-0-Jst-4-Pin-Connector-Plug-Male-With-100mm-Cable-Femal/331834602745

Don't forget mast with rod (I use 12cm rod) that puts your mag away from currents, mast must be not rotating (best two mounting screws or more). If you have problems with I2C going down, you might need pull-up resistors (check forum for values) or if you have scope how signal looks. If you have Spark2 try using Flexi port instead of I2C it might have stronger pull-ups or keep wires short.

To avoid problems with messing up with I2C I suggest Genuine DJI GPS. Make some adapter or cut cables and replace connector. DJI needs only one connection and does not use I2C protocol, but sends GPS serial data augmented with Mag read-out. It's a bit more robust against noise on the data wires imo, no possible pull-up problems and takes only one port, so other one you can use for OSD or something else.

[federicodl]

Yes I use that one, after changing connectors to JST-SH 1.0 with 4 pins.
http://www.ebay.com/itm/20-Sets-Mini-Micro-Sh-1-0-Jst-4-Pin-Connector-Plug-Male-With-100mm-Cable-Femal/331834602745

Don't forget mast with rod (I use 12cm rod) that puts your mag away from currents, mast must be not rotating (best two mounting screws or more). If you have problems with I2C going down, you might need pull-up resistors (check forum for values) or if you have scope how signal looks. If you have Spark2 try using Flexi port instead of I2C it might have stronger pull-ups or keep wires short.

To avoid problems with messing up with I2C I suggest Genuine DJI GPS. Make some adapter or cut cables and replace connector. DJI needs only one connection and does not use I2C protocol, but sends GPS serial data augmented with Mag read-out. It's a bit more robust against noise on the data wires imo, no possible pull-up problems and takes only one port, so other one you can use for OSD or something else.

this is what you mean?
http://www.banggood.com/Mini-Ublox-M8N-GPS-Module-NEO-M8N-GPS-for-APM-2_52_62_8-CC3D-SP-Racing-F3-Naze32-Flip32-PX4-p-1035454.html?rmmds=search

I can use FlexiPort to connect the gps? because the main port is already occupied by s bus receiver.

[Mateusz]

this is what you mean?
http://www.banggood.com/Mini-Ublox-M8N-GPS-Module-NEO-M8N-GPS-for-APM-2_52_62_8-CC3D-SP-Racing-F3-Naze32-Flip32-PX4-p-1035454.html?rmmds=search

No that's not DJI GPS. For reference I find one here http://www.helipal.com/dji-gps-module-for-naza-m-multirotor-gyro-system.html for $39. They cost around $40.
It's part of DJI eco-system. You just need to change connector. There are also "compatible" GPS modules, but some of them tend to hang, so I suggest getting official one.

I can use FlexiPort to connect the gps? because the main port is already occupied by s bus receiver.

No, GPS goes to main-port. GPS uses serial protocol (UART) and communication goes over DJI proprietary protocol which was reverse engineered and Revo can decode it.
Since Mag data are combined in GPS messages, so you don't need additional wires for Mag.

That leaves you with Flexi Port free which you can use for Sbus (I do) and on Revo you have also Flexi-IO (aka receiver) port, one with 8 lines, check wiki to see which of these lines are TX,RX for serial connection, those can be used for sending telemetry to OSD. Then you would have GPS+MAG, Sbus and OSD connected.