ublox ZED-F9P Differential GNSS Module

[kikass13]

Hello,

We have implemented a very simple rs232 driver for the ublox ZED-F9P differential gnss module.

The source code is here:

• https://github.com/DroidDrive/ublox_modm_example

The zed-f9p needs proper configuration. I have prepared this repository (utilizing wine & docker), so that a user can configure the ublox module properly (configure the UBX messages for example) via the u-center tool:

• https://github.com/DroidDrive/ublox_gnss_testbench

The specific breakout board we are currently using is SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic)

general

The driver is very simple and has some problems, but it works fine.
Currently, these UBX messages are implemented:

• UBX-NAV-STATUS
  • contains rtk information and general status flags
• UBX-NAV-CLOCK
  • contains clock and time information (drift, etc)
• UBX-NAV-PVT
  • contains a lot of information regarding current geolocation (lat, lon) and other stuff liek speed, heading, altitude etc.
• UBX-NAV-COV
  • contains covariance matrix for NORTH / EAST / DOWN position and velocity

what does it do

The driver simply polls for a byte and pushes it into the driver. The driver will receive data until a full frame was received. The Driver will then perform CRC checks and validate the frame. If the frame is valid, the data is parsed (put into a struct) and given to the user via callback.

current problems

• maybe someone can tell me, if a larger uart buffer is possible
• and how I can transfer uart data via dma & interrupt in modm.

[salkinium]

maybe someone can tell me, if a larger uart buffer is possible

There is an lbuild option for buffer.tx and buffer.rx sizes for all UARTs. Tops out at 64kB, although I think that's just a software limitation. (Although I would assume that 64kB per direction is enough?).

and how I can transfer uart data via dma & interrupt in modm.

Sorry, it's not implemented yet, although I would assume that you can orient yourself on the DMA SPI Master if you want to implement it yourself.

FYI: I also did a project with some UBX parsing and found these comms libraries to be quite useful. Not sure if that applies to your project though.

[kikass13]

There is an lbuild option for buffer.tx and buffer.rx sizes for all UARTs. Tops out at 64kB, although I think that's just a software limitation. (Although I would assume that 64kB per direction is enough?).

is this documented somewhere?

Sorry, it's not implemented yet, although I would assume that you can orient yourself on the DMA SPI Master if you want to implement it yourself.

well thats tough luck i suppose .. :(

FYI: I also did a project with some UBX parsing and found these comms libraries to be quite useful. Not sure if that applies to your project though.

yeah i saw that. but i did not want to bother with code generation for simple structs (or dynamic parsing). I just wanted to implement a small solution without the overhead.

[rleh]

https://modm.io/reference/module/modm-platform-uart-lpuart1/

[salkinium]

is this documented somewhere?

Yes, lbuild discover -n "::uart:*" and ideally also on the homepage, but apparently not on modm.io since I excluded the peripheral instance modules to cut down on the number of modules. Hmpf, the issues never stop… 😒