Emlid

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RTKLIB with Navio+ and NEO-M8N Chip


(Jeremy) #1

Just purchased a Navio+ and was wondering about eventually using the RTKLIB on my RPi2 with it for more precise positioning.

The original Navio (Navio Raw) came with a NEO-6T Ublox GPS receiver chip that allowed for the raw pseudo range data to be output straight off the board. The “better” Navio+ has a NEO-M8N chip` that DOES NOT output the raw pseudo range data (or timing, “T”) right off the chip.

NEO-M8N https://www.u-blox.com/en/product/neo-m8-series
NEO-6T https://www.u-blox.com/en/product/neolea-6t

Can you run RTKLIB with the Navio+ native NEO-M8N chip? My assumption is no.

Please tell me it isn’t true.

Jeremy


#2

NEO-M8N does not support raw-data officially. However, it is known that some F/W version can be configured to output raw-data as TRK-MEAS and TRK-SFRBX messages. I confirmed it by F/W version 2.01. The latest RTKLIB (2.4.2 p11) can also handle such messages. For details, refer the following material.


I found some limitation by M8N compared to M8T.
(1) Raw message can be used only with 1 Hz (NG with 5 Hz).
(2) Only GPS ambiguities can be resolved (NG for GLONASS or BeiDou)
Again, these are not supported by u-blox formally. Other F/W versions may not support them.

Tomoji Takasu


(Jeremy) #3

So basically… Navio stripped off the ability to do RTKLIB natively on the Navio+ board, put it on their REACH module, then charge you 5 times more? Whats even more funny is that originally they had extra NEO-6T modules which they were put on a usb dongle for $50… but now REACH costs $570?

I’ll stop complaining now, but here’s my request to please put the timing enabled ublox chips BACK on the Navio? Call it Navio 2.0??

Jeremy


(Andrea Celani) #4

Hi Tomoji,

thank you for sharing your useful test info. BTW your entire work is really amazing!
I came up against similar limitation using Navio+ with M8N as stated here: RTK and Navio
Other people here: http://www.gpsforum.geospector.de/phpbb/viewtopic.php?f=3&t=3503&start=15 says M8N is capable to handle raw messages at 5Hz (even 10Hz) disabling glonass and SBAS.
Have you experienced this behavior?

(I almost agree with @jstromsoe. While Emlid is a company and it has to make money and I have nothing against this I think there was a communication error with the name “Navio+”, maybe putting extensively that M8N has not the same performances of NEO-6T in terms of raw messages and RTK, IMHO)


#5

I wonder if the M8N and M8T have compatible pinouts, and we have an option to de-solder the M8N chip on the Navio+ and replace it a M8T?


#6

I have checked the datasheets and the pinouts are indeed compatible, the M8T has one extra pin (external interrupt) which I presume is not needed.


(Igor Vereninov) #7

Jeremy,

I think that there is some misunderstanding here. Navio did not strip off anything. It was made to be used as a platform for APM, yes we had a RAW version with NEO-6T, but it was not very popular. It does not make sense to put M8T in each Navio+ as it will increase price significantly for everyone.

Reach does not cost $570, this is the price for 2 Reach RTK + 2 Tallysman antennas. Also, each Reach includes Intel Edison processing module with Wi-Fi and BT. Single unit is just 225$.

@keithc You can desolder M8N and put M8T in its place, they are compatible, however that will void your warranty.


(worldburger) #8

@ivereninov is there a reasonable way to do RTK with Navio2 and a second external ublox M8N GPS on a RPi 2/3?

I’d love to be able to afford the Reach, but I think it’s just too far out of our budget for now (school autonomous project).

Any suggestions would be greatly appreciated if there are any errors in my hardware/idea!


#9

Yes, but no.
See my topic about it.