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Shoka
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RPI_GPS_ADD-ON_V2.0

Wed Jun 13, 2018 7:55 pm

https://www.itead.cc/wiki/RPI_GPS_ADD-ON_V2.0

I have one of these running happily on a Pi 3B+ as a GPS interface, and clock source.

It includes a microSD slot, that I can find no details of at all on the website.

From the schematic, and the pin table in the documentation, it seems to be connected to gpio's 8 through 11, which I believe means its connected to the SPI bus.

I've enabled SPI and I have two spi devices showing in /dev.

I'm not having much luck Googling for details of drivers to to handle a microSD on an SPI bus.

Any hints appreciated...

Hints to get the GPS functions on this board working on th Pi 3B +
  • Drop Bluetooth, restore the hardware serial port.
  • The PPS pin is not connected anywhere specific on the board, so patch the PPS pin with a hard link to a suitable GPS pin on the board
  • Install the PPS driver, configure the appropriate pin to the PPS driver in config.txt.
Cheers Harry

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bensimmo
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Location: East Yorkshire

Re: RPI_GPS_ADD-ON_V2.0

Thu Jun 14, 2018 8:14 am

Not sure why you need to turn Bluetooth off.
It should work (ublox6) off the noraml /dev/serial0 line once you have Enabled the Serial Port and Disabled the Serial Console.
The only reason would be to take the full UART, but I've never needed to.

(that's with 3B and ZW's though, 3B+ should be the same)


I would think it was similar to the V1 looking around that site.
which gives links to github
https://github.com/mcauser/Raspberry-Pi ... GPS-NEO-6M
there is also a schematic.

You could create a ticket with itead for more info if that doesn't work.

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Shoka
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Location: Manchester, UK

Re: RPI_GPS_ADD-ON_V2.0

Thu Jun 14, 2018 11:46 am

You need the hardware serial controller for reliable operation of the GPS function. In theory you can enable Bluetooth on the software serial interface, as was done for Pi's before the 3B+, but it's going to be less reliable than the default hardware set up on the Pi 3B+, and I don't need Bluetooth on the Pi based stratum 1 unit I'm building, so I just disabled it. Ergo I've not tested how well it works on the software UART, if at all.

Surprisingly that github info does not mention the Pulse Per Second set up, a much more accurate timestamp arrangement, that the Itead hardware does support, and there is a nice PPS kernel module to interact with it as well. From inspection of the hardware and the schematic, the PPS output is presented on a dedicated pin, and all that is needed in hardware is to jumper that pin across to a suitable gpio.

I have SPI enabled, their are two SPI devices showing in /dev.

Where I'm stuck is how to tell the kernel that that one of those SPI devices is an SD card, and please to use it as a disc. I'm not sure if its simply a matter of configuration, or is there a lump of software I'm missing...

No mention of that step I can find in any of the documentation.

I guess I'll have to go back to Itead.

Harry
Cheers Harry

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bensimmo
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Re: RPI_GPS_ADD-ON_V2.0

Thu Jun 14, 2018 12:35 pm

It's 3 years ago and for version1, but it's the same hardware ublox6 hardware.
https://github.com/mcauser/Raspberry-Pi ... M/issues/2
But that'll not be for a stretch based Raspbian setup.

PPS I don't think is special to that device
The dtoverlay readme is https://github.com/raspberrypi/linux/bl ... ays/README

And a forum Search shows a few up , one form late 2017.


Unfortunately no idea on the SD card.

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Shoka
Posts: 147
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Location: Manchester, UK

Re: RPI_GPS_ADD-ON_V2.0

Thu Jun 14, 2018 6:31 pm

PPS is a standard function of some GPS chip sets, not peculiar to the Neo used in the Itead board, but having PPS available on a gpio pin pin rather than on one of the UART control lines, is only common on the Pi, and makes them an unusually good platform to create a reference timeserver. I did not mean to imply that the Itead board was particularly unusual in having PPS available, only that the Itead documentation makes almost no reference to it, and it's a valuable feature. The modular kernel PPS driver may be recent, older information suggests that you need to recompile the kernel to get this feature, but this is no longer necessary. Maybe the difficulty of implementing a kernel PPS service is why Itead don't make more of the feature.


Harry
Cheers Harry

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