[time-nuts] Re: Seeking info on Ericsson NCD 901 56/1 devices

[Daniel Watson]

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 at 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.
>