Page Comparison

• Inspiration

  • LTE Breakout

  • RPI Interface Rev B

• Who

  • Daniel Puratich hardware design

  • Anthony Luo device selection, firmware

• Features we aren’t adding but considered

  • no ELRS

    • ELRS changes a lot quickly

    • could be saved for a future revision

  • no cameras

    • mounting a camera makes placement complicated

• Features

  • Begin from RPI Interface Rev B

    • Keep the UART killswitch and one UART passthrough for the RPi to FC direct

      • Being implemented in the stm though instead of the hardware switch

      • This is being done to avoid running out of UARTs on the STM and to avoid hardware complexity

      • UART forwarding can be done with DMA so it can be fast and not very resource intensive.

    • Keep UART LED indicators

      • this is nice for debugging

      • costs some board space

      • could be DNPed in a final version

    • Keep CAN circuit

      • this can be used to control the lighting system if we wanted to?

      • Could also connect to pixhawk for mavlink over CAN if we’re able to do the required firmware to make this solve.

  • Add LED features

    • Some neopixels on the board might be nice.

    • Leds on the pwr rails since I have space.

    • IR detector so we could use one of those cheap remotes to control LEDs.

  • Analog Monitoring

    • STM has some spare analog pins so might as well use them

    • temperature and voltage monitoring

  • Add an LTE modem to RPi interface rev c

    • relevant discord chat & here

    • quectel module he put

    • Quectel gets USB into the RPi and the STM. RPi eill be used initially and is drawn below because it requires less custom firmwqre, but using the stm long term seems nice.

    • Selected to get maximum mavlink datarate out of the Pixhawk

    • This is not intended to be able to stream data for “groundside compute” for autonomy proccessing as explained in https://uwarg-docs.atlassian.net/wiki/spaces/ARCHS22/pages/2669412363/Autonomy+Compute+Integration+2025?search_id=fe948f35-631d-416c-b4d9-095d8cab5e37.

  • Change buck converter to support 48V input so we can connect VBATT

    • this makes architecture decisions and harnessing easier

  • Switch STM32

    • STM take in the three uarts form quectel

    • The other STM is smaller and doesnt have enough UARTs for this

    • STM will communicate with the RPi over SPI

  • Increase board size a bit

    • this turns the board into a full normal RPi hat

    • This is required for cooling for the LTE module and a simple USB connection for the LTE hat

• Part Numbers

  • EG915NEAAC-N05-SNNSA

  • STM32F415RGT6

• Why

  • Unlimited range & unlimited datarate is really attractive even if it comes at the cost of some weight and some power consumption.

  • Maintaining C2 link is required for flight so full reliance on ELRS is scary even if we have overwhelming evidence for it’s reliability

• Block Diagram

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