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Re: u-blox : layers are confusing me
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From: |
Gary E. Miller |
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Subject: |
Re: u-blox : layers are confusing me |
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Date: |
Sat, 20 May 2023 11:40:08 -0700 |
Yo Hans!
On Sat, 20 May 2023 15:43:51 +0200
Hans Mayer <gpsd@ma.yer.at> wrote:
> U-blox ZED-F9P with version 27.12
Nice. What port are you using? The USB? Serial? I2C?
> gpsd: 3.25.1~dev (revision release-3.25-48-gfa2081388)
Good. The next thing I need is the complete, untouched, output of:
ubxtool -p CONFIG
ubxtool -p STATUS
> I am trying to understand the layers, especially with the baudrate
> configuration.
Good luck. The new u-blox layers confuse everyone.
The short answer is that every value actually has 7 layers, and the
value set in the highest priority layer wins. Spend some quality time
reading Section 5.3 of this:
'ZED-F9P_InterfaceDescription_(UBX-18010854).pdf'
> This is the situation after a RESET
Which kind of RESET? There are many kinds, each slightly different.
> UBX-CFG-VALGET:
> version 1 layer 0 position 0
> layers (ram)
> item CFG-UART1-BAUDRATE/0x40520001 val 38400
One of the 4 possible layers, you only retrieved the value from layer 0
(RAM). A speed of 38.400
> UBX-CFG-VALGET:
> version 1 layer 7 position 0
> layers (default)
> item CFG-UART1-BAUDRATE/0x40520001 val 38400
One of the 4 possible layers, you only retrieved the value from layer 7
(default). A speed of 38.400
> /ubxtool -z CFG-UART1-BAUDRATE,115200,0 localhost:gpsd:/dev/serial0 /
>
> and I am wondering why gpsd can still access the device with 38400 bd
If you look at the doc for UBX-VAL-SET, you'll see you can never set
layer 0. Layer 0 is computed from the other layers.
The "layer" in VAL_SET is not an integer like you are thinking, it is
a bit map. Bit 1 is to set layer 1, bit 2 is to set layer 2, and bit
trhee is to set layer 4.
So the layer value can be 0 to 7, each with this result:
0 - nothering
1 - set layer 1
2 - set layer 2
3 - set layers 1 and 2
4 - set layer 4
5 = set layers 1 and 4
6 - set layers 2 and 4
7 - set layers 1, 2 and 3
Are you sure you have Battery Backed Ram (BBR) on your board?
> /ubxtool -z CFG-UART1-BAUDRATE,115200,1 localhost:gpsd:/dev/serial0/
>
> Now communications is broken to the ZED-F9P. I have to reconfigure
> the gpsd with 115200 bd
As expected and documented.
> The ZED-F9P interface
> description PDF is in general very useful but didn't give me a
> solution for my question.
I'm unclear exxactly what your question is?
Does my explanation above help?
> It seems there is sometimes an offset of 1 but not always
u-blox layers have vexxed many people. The answers really are in the doc.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
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"If you can't measure it, you can't improve it." - Lord Kelvin
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