Hi

I believe you will find that most of the standards in the TimeSource boxes
do not have the PPS disciplining option built into them. Next layer to the
problem is that even if they do, the algorithm used is not really up to the
task of dealing with a GPS PPS. There are a range of issues that come up….

The main reason these boxes flooded eBay a decade or more ago was that
CDMA turned out to be a less than ideal time source. They mostly are useful
as a (hopefully cheap) source to pull a standard out of …..

The best way to discipline the source is to use the tuning voltage input and
drive it with custom hardware to lock to GPS.

Bob

There is also another version of these Ericsson GPS receivers floating
around - this one is marked "GRU 04 01" - physical construction is very
similar, but this one appears to be manufactured by Trimble.

Operationally, it's almost identical to the GPS 0301 described earlier, and
produces mostly the same output, except that it has an extra
$PERC,GPpps sentence that the earlier model didn't.  From the look of the
board, it's using the same (or very similar) GPS module, but
with modified internal firmware so that it directly outputs the Ericsson
messages rather than having to have the STM32 to translate the output.

https://i.ibb.co/VmSLFSP/IMG-3625.jpg
https://i.ibb.co/gg86jQw/IMG-3626.jpg
https://i.ibb.co/7R1TBR0/IMG-3627.jpg

From a hackability point of view, the GPS 0301 looks like a better bet.

Regards,

Pete Bell

On Wed, Aug 10, 2022 at 9:39 AM John Miller via time-nuts <
time-nuts@lists.febo.com> wrote:

My units came in yesterday and I have had good luck with them, so far. Very fast lock.
Interfacing with them is easy enough. The pinout on the osmocom site is correct indeed,
and RS422<->UART devices are actually not required - the voltage levels are 3v3, so
standard USB-UART devices connected to the "+" sides of Rx and Tx work just fine.

If you connect a standard T-568B ethernet cable to the jack, the pinout is:

(2) Solid Orange - PPS
(4) Solid Blue - Tx (Data from GPS)
(6) Solid Green - Rx (Data to GPS)
(7) Brown White - 12v
(8) Solid Brown - GND

Each RJ45 connector outputs identical signals and has identical pinouts.

The default UART data is sent 9600 baud, 8n1. The data sent is a curious Ericsson
protocol, and I have not been able to find complete documentation on it as of yet.
I believe that the document that may contain the specs for this protocol is titled
"IWD L2 L3 GPS Digital Interface" but I have not been able to find reference to it other
than in a thesis written in 2012.

Every second, two sentences are sent. $PERC,GPsts which is alleged to be the GPS
status, specifically if it's in acquisition mode, surveying, position-hold, or surveyed in. I have
had one unit running for over 12 hours continuously and it has not left "position-hold"
mode. The second sentence sent is $PERC,GPppr, a "periodic PPS report" which
includes GPS TOW, GPS Week, number of satellites used to compute the fix, and
maybe more - the documentation is incomplete.

Every 60 seconds it sends a handful of standard NMEA sentences: GNGSA, GPGSA,
GLGSA, GPLSV, GPGSV, and GPGGA. A few other Ericsson PERC sentences are
sent as well. an "averaged position" sentence, and a sentence with date & time.

I don't yet know if there are any commands we can send to the unit to enable it to
begin a survey or alter the strings transmitted. I imagine that there are but we need
to get our hands on the protocol documentation first.

At this point, my suspicion is that to get the best value for money out of these things,
one should tap the UART & PPS signals directly off of the RES SMT 360 module itself and
bypass the SMT32 entirely.

Regards,
John
KC1QLN

If we could figure out the protocol Lady Heather could be configured to
work with it.  That would be neat.  I found some ATT documentation showing
a picture of multiple (maybe 8-10) of these mounted in the bottom of the
rack all getting GNSS signal off a splitter connected to one antenna and
each unit fed to different ground base station radios.  I tried searching
but Ericson seems to really hide it's documentation.  Some of the few
references were companies charging for training classes and test quizzes
for techs studying to work on base stations.  Ericson has a website with
all the docs behind a customer/technician login... reminds me of how
Symmetricom always was.

Bill E.

On Tue, Aug 16, 2022, 1:55 PM John Miller via time-nuts <
time-nuts@lists.febo.com> wrote:

I've been playing with some of the GPS 03 01 modules and here's a quick
hack to get them working with
Lady Heather.

Unfortunately, it does require opening the module up and some soldering,
but it's not very complex.  Start by
removing the 33R series termination resistor on pin 42 of the STM32F105,
then solder a wire between the pad
for the far end of the resistor (I.E. the one not connected to the STM32)
and pin 17 on the Trimble module.

This results in RJ11 port #1 operating as before (I.E. Ericsson flavored
NMEA), but RJ11 port #2 now outputs
TSIP at 38400 baud.  The downside is you have no control over the receiver
, since it's still being driven by the
STM32.

On Wed, Aug 17, 2022 at 8:03 PM Bill Notfaded via time-nuts <
time-nuts@lists.febo.com> wrote:

Hi,

Here is the rest of the pin mapping for the serial ports on the GPS and
STM32:

GPS TXDA (Pin 17)  ->  STM32 USART3_RX (PB11 Pin 30)
GPS RXDA (Pin 16)  ->  STM32 USART3_TX (PB10 Pin 29) through 33R resistor

GPS TXDB (Pin 22)  ->  STM32 USART4_RX (PC11 Pin 52)
GPS RXDB (Pin 21)  ->  STM32 USART4_TX (PC10 Pin 51) through 33R resistor

STM32 USART1_TX (PA9  Pin 42)  ->  AM26LV31E (Pin 7) through 33R resistor
for RJ45 #2 TxD
STM32 USART1_RX (PA10 Pin 43)  ->  right MAX3280 (Pin 3) through 33R
resistor for RJ45 #2 RxD

STM32 USART2_TX (PA2  Pin 16)  ->  AM26LV31E (Pin 15) through 33R resistor
for RJ45 #1 TxD
STM32 USART2_RX (PA3  Pin 17)  ->  left MAX3280 (Pin 3) through 33R
resistor for RJ45 #1 RxD

I expected the quad line driver to be used for serial Tx/Rx for the two
RJ45 ports, but actually it's used for Serial Tx from the microcontroller
and the PPS. The Serial Rx lines are handled with separate MAX3280
converters.

Serial port A on the Trimble is definitely the important one. The STM32
sends configuration messages to the GPS on this port at power on, and then
other occasional messages. There doesn't seem to be much activity at all on
serial B. Perhaps they hooked it up as a "just in case".

It might be possible to achieve full serial access on RJ45 port #2 with the
help of a small microcontroller with two serial ports. Have it receive the
messages coming from USART3 on the STM32 as well as messages from RJ45 port
#2, and then combine the two serial streams to send them to GPS serial A.
There might be some timing issues... but hopefully it's just a matter of
giving priority to the STM32. I have an ATTINY841 on hand that would be
perfect for the job. Maybe I'll try to rig that up and report back.

Thanks

Dan

On Sat, Aug 20, 2022 at 9:55 AM Peter Bell via time-nuts <
time-nuts@lists.febo.com> wrote:

And here is a hex dump of the first 65 seconds after power on of the
communication between the STM micro and the Trimble GPS receiver
RX is send to the GPS
TX is send from the GPS
The LED started blinking after about 20 seconds
The log ends after the GPS lockd and the LED became steady on
Messages start with '10' and end with '10 03'

http://athome.kaashoek.com/time-nuts/trimble_log.txt
Is someone able to decode if the STM is doing something special with the
Trimble?
Does the Trimble support something like the qErr messages?

Erik.

Op zo 21 aug. 2022 om 08:30 schreef Daniel Watson via time-nuts <
time-nuts@lists.febo.com>: