[TangerineSDR] MagnetoPi Hat schematic posted to TangerineSDR Documents folder

[Tom McDermott]

Hi Scotty - I find the schematic difficult to understand because there are
so many placeholders for things that are not implemented, but might be
implemented in the future.
Without knowing what the future is, why the further things are the way they
are, what the various connectors might or might not do, it is nigh
impossible to know what is done and why.

So, ignoring all that, here are comments:

1. AVDD and DVDD are tied together on the PNI sensor board. Do these need
to be separately decoupled?  Will noise on
the DVDD mess up the AVDD signal?

2. I'm confused about Pin 6 (GND) of the RPI connector, pullup R10 and
strap JMP4.
The notes on the schematic aren't enough for me to sort all this out and
what is going on here.
Maybe a table would help.

3. Dave had an initial problem with the I2C differential driver/receiver
where there was an RC delay needed. Assuming you are
using the same component, I think this may have this problem.  U7, pin 2
should not be tied to VCC but to an RC delay network.

Here is my comment to Dave on January 27th:
> The power supplies need to sequence up cleanly for the internal
Power-on-Reset of the extender chip to initialize
> properly.  The EN pin must be low during power stabilization then
transition to high more than 11 milliseconds after power is applied.
> The datasheet says that it is not allowed to transition high sooner than
11 ms after application of power. [Figure 6 of
> the datasheet, section 7.4]. Since you have it hard-wired to +3.3V, I
suspect this could be one problem. If you do
> not have logic tied to this pin, then an RC delay circuit may be needed.
I'd look at the Sparkfun circuit and see
> how they do it.

My recollection is Sparkfun did it wrong also...   When Dave fixed this it
started working.

-- Tom, N5EG




On Tue, Aug 4, 2020 at 3:10 PM Scott Cowling via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> The final schematic of the Raspberry Pi Magnetometer Hat board is up in
> the TangerineSDR documents folder.
>
> Before we pull the trigger on a proto build please take a minute to
> review it and comment.
>
> This board is complete including layout and BOM, so hold any changes in
> functionality for rev 2. We just need to make sure there are no errors.
>
> Several of you have seen this before and commented. I tried to include
> all of your suggestions in this final version.
>
> So let's see how I did! :-)
>
> Here is the link:
>
> >
> https://tangerinesdr.com/TangerineSDR_documents/MAGNETOPIHAT_SCHEMATIC_XA9.pdf
>
>
>
> 73,
> Scotty WA2DFI
>
>
>
> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>
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