[TangerineSDR] TangerineSDR Digest, Vol 31, Issue 1
Julius Madey
hillfox at fairpoint.net
Sun Oct 3 15:47:06 EDT 2021
Bill,
This is the i2c address space of the 9808 and RM3100 per the data
sheets......0 is ground and 1 is Vdd
I think you meant that JMP4 in the second column should be JMP1 rather
than the other way round. JMP4 is the shield ground.
When the local board is plugged on the Pi 40 pin header as a PiHAT, A0
is pulled low, which limits the possible address space for the RM3100 on
the local board to 0x20 and 0x22, and the local 9808 to 0x18, 0x1A, 0x1C
and 0x1E.
For the remote board, all addresses in the above table are
available......except that used for the 9808 on the local board. If no
address jumpers are installed on the local board, then 9808 addresses
0x19 through 0x1F are available at the remote.
Note that no more than four RM3100s can be used on the same i2c bus ...
expansion beyond that requires an i2c multiplexer like the TCA9548a
which Dave Witten and I were considering for a test board for the RM3100
that would service some 32 RM3100s.
CAUTION regarding the note under extended mode in the address tables and
the use of multiple 9615 differential i2c drops on the CAT5 or CAT6
cable. Read the 9615 data sheet carefully on the subject of multiple
drops .... intended for short (~ 3meter cable runs) at a 1MHz bus
speed. My testing to 400+ feet was with only a local and remote board
at 100KHz bus speed which demonstrated well behaved transmission line
behavior for the ~100ohm twisted pair lines in the cable with no
reflections and no transient spikes.
The 9615 data sheet example for multiple drops on the differential lines
show NO termination resistances on the intermediate drops and only line
terminations at the beginning and end 9615s. I'm going to hazard a
guess that you might be able to use 100 feet or so of cable with a
couple of intermediate drops within 3 or 4 feet of the remote end and NO
terminations on the 9615s on those boards but would have to actually
scope test that to verify.
The only multiple mag install on a single CAT cable I am aware of is the
one I'm using here with two RM3100 remote boards within about 3 inches
of one another connected only by ground, +3.3V, SDA and SCL (eg i2c bus
connections only).
Regards,
Jules-K2KGJ
On 10/2/2021 11:36 PM, Bill Owens wrote:
> I did get the email - thank you! I looked through the info on the
> second page of the PDF and I have some questions, but it does confirm
> that there are options for as many as four sensor boards, which fits
> with what I was considering.
>
> I think the box below the I2C table is wrong for the MCP9808; the
> addresses should be 0x1E and 0x1F per the table, and the callout in
> the schematic. It also mentions JMP1 in the second column, I think
> that should be JMP4.
>
> I also noted that JMP4 is described as being set only on the local
> board in most locations, but shown as "Placed" on the remote board in
> the NORMAL MODE and EXTENDED MODE boxes.
>
> I'm curious about whether there's a plan for deploying multiple
> sensors; one of the notes implies that, without giving any other
> details. Would it be a star configuration with the Pi at the center,
> or a daisy-chain using both the RJ45 and J10 for the boards in the middle?
>
> Thanks,
> Bill N2RKL
>
> On Sat, Oct 2, 2021 at 1:54 PM Julius Madey via TangerineSDR
> <tangerinesdr at lists.tapr.org <mailto:tangerinesdr at lists.tapr.org>> wrote:
>
> I answered Bill a few days ago....perhaps he didn't receive the
> email. I forwarded the latest schematic and layout for the board
> which has a section on setting i2c addresses. Perhaps Scotty can
> update that further.
> Jules-K2KGJ
>
>
> On 10/2/2021 12:00 PM, tangerinesdr-request at lists.tapr.org
> <mailto:tangerinesdr-request at lists.tapr.org> wrote:
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>> Today's Topics:
>>
>> 1. FW: [HamSCI] Two questions about the new TAPR magnetometer
>> board (Dr. Nathaniel A. Frissell Ph.D.)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 1 Oct 2021 16:22:25 +0000
>> From: "Dr. Nathaniel A. Frissell Ph.D."
>> <nathaniel.frissell at scranton.edu> <mailto:nathaniel.frissell at scranton.edu>
>> To:"tangerinesdr at lists.tapr.org" <mailto:tangerinesdr at lists.tapr.org> <tangerinesdr at lists.tapr.org> <mailto:tangerinesdr at lists.tapr.org>
>> Subject: [TangerineSDR] FW: [HamSCI] Two questions about the new TAPR
>> magnetometer board
>> Message-ID:
>> <BLAPR03MB5540044997C2145BB6D46D2AF2AB9 at BLAPR03MB5540.namprd03.prod.outlook.com> <mailto:BLAPR03MB5540044997C2145BB6D46D2AF2AB9 at BLAPR03MB5540.namprd03.prod.outlook.com>
>>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> Hi,
>>
>> I'm sending these questions from Bill N2RKL to the TangerineSDR list. They were originally posted on the HamSCI list.
>>
>> 73 Nathaniel
>>
>> From:hamsci at googlegroups.com <mailto:hamsci at googlegroups.com> <hamsci at googlegroups.com> <mailto:hamsci at googlegroups.com> On Behalf Of Bill Owens
>> Sent: Thursday, September 30, 2021 9:22 AM
>> To: HamSCI<hamsci at googlegroups.com> <mailto:hamsci at googlegroups.com>
>> Subject: [HamSCI] Two questions about the new TAPR magnetometer board
>>
>> I've listened to the last couple Zoom sessions and also found the layout pictures that Scotty showed a few weeks ago, but I haven't been able to work out answers for two questions:
>>
>> - How many I2C addresses can be set for the magnetometer and the temperature sensor on each board?
>> - Are the RM3100 components soldered on the boards, or perhaps on half of them? It looks like there are options for SMT header sockets, and for the components themselves.
>>
>> Thanks,
>> Bill N2RKL
>> --
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