UBlox Neo-6m accuracy with MWC SE V2.5

[brewski]

Hi,

I see the Ublox Neo-6m selling for $20 on EvilBay. They seem to come in two styles ne with external antenna & one all on the interface board. Not sure which is best, but I'm guessing with the external antenna you can mount it above quad as I have seen some do.
Does anyone have one of these cheap Ublox units connected to Crius SE V2.5 or clone & if so how accurate is position accuracy.

My other query is connecting one of these GPS units to the FC. It appears that the above units output serial data. Both the FTDI & UART ports use serial data but which one does the MW2.3 sketch use for GPS?

Cheers..B

[QuadBow]

if so how accurate is position accuracy.

The accuracy is not the issue for the UBLOX based gps device and should be independed from the flight controller.

My other query is connecting one of these GPS units to the FC. It appears that the above units output serial data. Both the FTDI & UART ports use serial data but which one does the MW2.3 sketch use for GPS?

You have to connect it via an I2C_GPS_NAV module iwth the proper firmware http://code.google.com/p/i2c-gps-nav.
However, you have to patch the software http://code.google.com/p/i2c-gps-nav/issues/detail?id=6 since the initialisation fails otherwise.

My recommendation would be to take a better flight controller, based upon an ATMega2560 with more serial ports for a direct connection and more flash memory, which will be enough for future extensions (like waypoint navigation which is announced for multiwii 2.4).

[brewski]

Hi Quadbow,

Thanks for the info. So GPS must connect only to I2C port & as these cheap GPS Ublox neo-6m only output serial data when using Crius Se 328 type boards you need a converter module but if you use one of the Pro 2560 based boards you don't require an interface?
On the 328 type boards they have a serial UART port so why can't GPS connect to this?

I agree the Pro 2560 type boards are the way to go when you start adding things like GPS. I'm only using the Crius SE V2.5 because it came with the X525 kit. It has been a good board to learn Multiwii on.

Cheers...B

[QuadBow]

It has been a good board to learn Multiwii on.

I agree with you that it is sufficiant for beginners.

On the 328 type boards they have a serial UART port so why can't GPS connect to this?

They have only one serial port which is used for the connection to the computer running the multiwiiconf program.

So GPS must connect only to I2C port & as these cheap GPS Ublox neo-6m only output serial data when using Crius Se 328 type boards you need a converter module but if you use one of the Pro 2560 based boards you don't require an interface?

Actually, all gps devices at a responsible price level use the serial port. So, one solution is to have that converter between the flight controller via i2c and the gps device via serial.
The issue with the converter board is that it requires an i2c bus with 5V. I do not know whether your board provides an ic2 bus with 5V or only with 3.3V.
The other issue is the failing gps initialisation because the cheap gps devices don't have an eeprom to store the connection parameters in.
The work-around for that is the firmware patch I mentioned before.
With an Mega2560-based board you get rid of all issues.

By the way, there is another short-term solution for the promini (328p) by defining
#define GPS_PROMINI_SERIAL // Will Autosense if GPS is connected when ardu boots.
which "hijacks" the serial port for gps purposes. However, for my configuration the sketch is too big for the poor 328p. So, maybe you have to sacrify something like barometer or vbat or something else. I am coming always to the conclusion that the Mega2560 is the best solution in order to be ready for future extensions...

[brewski]

Hi Quadbow,

My board is an exact copy of Crius SE v2.5. It has 2 dedicated I2C ports with 5V, a UART serial port (TX,RX, +5 , Gnd) as well as an FTDI port (which appears to be a true serial port (RX, TX, DTR, CTS, +5 , GND).
The UBlox Neo -6m GPS modules I was looking at ($20-$27) all had EEPROM. The only difference was all on board or board +external antenna. Not sure which way to go.
What do you suggest?

I will definitely take your advise & upgrade my quad to Atmel MEGA 2560 based board in near future. Looking at my board I still have D5, D6, A0, A1, A2, A8, A7 and A3 (currently connected for voltage monitoring). Any of the analog inputs can be set as outputs in sketch so I still have quite a few outputs to play with. The 32K is probably the main limitation with the 328.

Cheers..B

[handsomejackuk]

bump this post for reference

[QuadBow]

The only difference was all on board or board +external antenna. Not sure which way to go.
What do you suggest?

I have never seen an UBLOX Neo-6m to be sold with external antenna. But, the antenna is only slightly glued and therefore removable. Are you sure that have not seen the gps device with i2c-converter called I2C_GPS_NAV included?

[handsomejackuk]

the ublox neo 6m unit i bought chinese cheap on on a pedestal has the mag included, think it was £12 also has backup battery and works well, i made a serial to i2c board to connect to my home built arduino atmega 328 flight controlller.

same setup as you are running... mine only had one serial port and that is being used for bluetooth communication via ez gui..... i made the serial to i2x board using another pro mini 3,0 board available very cheaply