Hi everyone.
Hi @sparky and @PaulZC
Is it possible to add an IMU19 to the Postcard RTK with the portability protector?
That would be great.
Regards, Angel
Hi Angel (@amlago ),
It is difficult… I have thought about it, but there is no easy way to connect up the UARTs.
The IM19 needs to be fed with NMEA GGA+GST+RMC at 5Hz. We could do that with the LG290P UART3.
It needs PPS too. We have access to the LG290P PPS signal.
But we also need to connect the IM19 to an ESP32 UART, so we can: configure the IM19, and receive the GPFMI NAVI messages containing the compensated position. There is no easy way to do that on Postcard. Or, at least, I can not think of one…!
(We do have new RTK products in the pipeline which include the IM19 for tilt compensation. But they are still in development… 
)
Best wishes,
Paul
Thanks, Paul. It was an idea.
There was a possibility it could be easy. Ja ja.
Regards, Angel.
Hi Paul,
Following your reply about the IM19 on Postcard — I think there may be a viable path.
LG290P UART3 is already routed out to the JST-GH connector and PTH pins. That’s the same port the IM19 uses for its NMEA feed on LG290P-based setups (COM3 TX → IM19 UART2 RX). So the GNSS → IM19 link is already physically available on the Postcard without any board-level rework. PPS is also accessible on GPIO 36.
For the missing ESP32 <> IM19 connection, if we sacrifice the microSD on the Portability Shield, GPIO 25 (POCI) and GPIO 26 (PICO) become free. ESP32 UART2 is unused on Postcard and can be remapped to those two pins. That gives us the link needed for AT configuration and GPFMI NAVI reception.
So the wiring would be:
∙ LG290P UART3 TX (JST-GH) → IM19 UART2 RX (NMEA GGA+GST+RMC)
∙ LG290P PPS (GPIO 36) → IM19 PPS
∙ ESP32 GPIO 26 (UART2 TX) → IM19 UART1 RX
∙ ESP32 GPIO 25 (UART2 RX) → IM19 UART1 TX
∙ 3.3V + GND from the board
The trade-off is losing microSD logging. On the firmware side, it would need pin_IMU_RX/TX definitions and tilt support enabled for the Postcard platform — I see the RTK Everywhere codebase already has LG290P tilt/IM19 support.
Do you see any showstopper?
Thanks!
Hi @marcuzz0 ,
Do you see any showstopper?
No… What you have proposed should work.. I am going to open a “Feature Request” for this on GitHub.
We do have IMU products in development, that match the 1.7" x 1.7" format of Postcard… Coming soon!
Best wishes,
Paul
Okay Paul, thanks for the info. I’ll do some testing in the meantime. Let’s stay in touch. Best regards,
Marco
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I did some outdoor testing and can confirm that it works.
Marco
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