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LoRaWAN Feather

An Adafruit-compatible, LoRaWAN-compatible board.

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A LoRaWAN Feather board based on the STM32L073 and DRF1262T radio module. Has all the awesome Feather features:
- USB
- LiPo charging
- I2C, SPI, UART, GPIO, Analog, DAC
- USER button and LED
With all the fun LoRaWAN features
- STM32L073 and SX1262 supported configuration for the Semtech LoRaWAN reference
implementation
With awesome upgrades!
- Efficient DC-DC buck/boost converter
- SWD connector
- Builtin LiPo Fuel Gauging
- Hardware support for a hard secure element

Designed to be machine built. Most of the PCB is, in fact, designed around the JLC SMT parts library.

Designed to meet the Feather spec and with LoRaWAN library compatibility in mind from the start.

Designed to be compatible with STM32CubeMX.

Should be hand buildable for anyone with some soldering skill if you want to get all the design files yourself.

Open source from the start!

Find the hardware on GitHub
Find the firmware on GitHub

PCB is laid out according to the Adafruit Feather spec.  The idea is to make it manufacture-able.  It could be sold as a finished board minus the headers, RF connector and the radio module.  All of those parts are easily hand solder-able. 

The radio module is by Dorji and is the DRF1262T.  It's FCC certified and is available on Tindie.  The module is based on the SX1262.

The board implements I2C, SPI, UART pins.  Implements 4 GPIO (one is connected to the SPI hardware NSS pin).  Implements 3 analog pins, one is a DAC pin.  The STM32L073-SX1262 combination is an out of the box supported configuration by the Semtech LoRaWAN reference implementation.  Has hardware support for the hard secure element.  Includes native USB with ESD protection and common-mode filtering.   Includes an efficient DC/DC buck boost based on the TPS63001 capable of supplying ~300mA@3.3V.  Includes the 2x5 0.05" (1.27mm) Cortex standard SWD connector.  Only implements SWDIO, SWDCLK and NRST (SWO is not supported on Cortex-M0+).

PCB was designed to be manufactured from the start.  Parts are based on the JLCPCB SMT program.  You can (currently) get the board assembled completely except for the connectors (JLC has no connectors in its SMT program) and a few of the parts that JLC was either out of, or didn't include in the program.  Those parts and their placement were considered so it is possible that they can be hand soldered.  The radio module is the only bottom side component which is easily hand solder-able.  The schematic includes Digikey part numbers for all the parts as well.

The GitHub repo contains all the hardware files to manufacture the board including BOM and CPL files, so you could, in theory, send these off to a PCB house and get the boards made on your own.

I've also put together an STM32CubeMX project file that is compatible with the board if you want to roll your own project.  This includes all the pin definitions that match up to the hardware.  Those pin definitions were carefully selected to match the default LoRaMac-node firmware pins.

loRaWan1262.ioc

STM32CubeMX *.ioc file that matches the Feather board hardware layout. Useful for starting a project based on this board.

ioc - 7.93 kB - 11/19/2019 at 14:27

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schematic.pdf

Circuit schematic

Adobe Portable Document Format - 402.92 kB - 11/18/2019 at 05:36

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pcbTOP.pdf

Fabrication layout of the top side of the PCB

Adobe Portable Document Format - 33.46 kB - 11/18/2019 at 05:37

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pcbBOT.pdf

Fabrication layout of the bottom side of the PCB (not much to see here)

Adobe Portable Document Format - 18.45 kB - 11/18/2019 at 05:37

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  • 1 × STM32L073 STM32 Cortex M0+
  • 1 × DRF1262T SX1262 Based LoRa radio
  • 1 × TPS63001 Power Management ICs / Switching Regulators and Controllers
  • 1 × STC3100 Power Management ICs / Power Supply Support
  • 1 × ATECC608A Crypto Co-processor

View all 6 components

  • Forgot to show you the bottom

    Andy12/04/2019 at 23:08 0 comments

    Just realized I didn't snap a photo of the underside with the radio module.  So here is yet another crappy photo

  • Update!

    Andy12/04/2019 at 23:02 0 comments

    Update on the project after the holiday!  I got in the semi-assembled boards from JLCPCB.  I'm very happy with the quality and speed of the assembly process.  The boards look great:  

    Sorry for my crappy photography skills.  JLC doesn't have any connectors in their SMT assembly library which is strange, so they aren't assembled.  The three user buttons were supposed to be assembled, but that was an error on my part.  I did not select a part on the BOM selection step of the process.  Oh well, Digikey to the rescue.  The rest of the parts were either not in stock or not available for assembly.  Time to get out my iron!

    I decided to start with two so that I can run the LoRaWAN stack's ping pong application as a test as well as get them connected to my Raspbery Pi based LoRaWAN gateway for testing.  However, some initial testing is in order first!

    To date, I've done a basic power on test using the 3.3V from a bench supply, the battery and 5V via USB and all function as designed.  This tells me that my DC-DC is working, as is the rest of the power system.  Battery charging also works.

    I loaded up a simple blinky application and it runs, proving my SWD and crystal circuits are working.  Only snafu there is that the LED is green instead of red!  Probably an error on my end again, but a minor one. 

    Only issue I've noticed so far is that I populated R16 and R17.  With the STM32 USB FS Phy, pullups on the D+/D- line aren't required, but I wanted to have the pads there just in case.  I'll have to desolder those when it comes time to test the USB.

    My next step is to write some basic code to test the battery fuel gauge and at least make sure I can communicate with the crypto coprocessor.

    So far, off to a good start! 

  • PCBs

    Andy11/19/2019 at 14:15 0 comments

    Looks like the missing parts were errors on my end (go figure).  The common mode filter for USB was out of stock and I didn't select a suitable replacement (which was available).  The switches were in the CPL file, but not the BOM so they won't be placed.  I've ordered the balance of parts from Digikey and should be able to finish off the boards by hand.  As of this morning the PCBs are almost done with production.  I've updated the schematic with part numbers from Digikey for all the parts.

  • PCB Production

    Andy11/18/2019 at 14:39 0 comments

    JLCPCB has started the production of the PCBs.  They passed the initial approval process.  I'm not sure if that process is automated or not.  According to the DFM analysis, it looks like I had my whole board rotated.  Not just footprints being rotated, but the entire board?

    The DFM analysis noted the following error "Cannot find this Pad in your PCB" for U1 and U6.  I'm guessing this means that it could not determine pin 1, but in both cases the parts are correctly placed.  Some parts that are on the assembly list don't show up in this rendering namely the switches and the common mode filter.  I've emailed to find out the details on that.

  • Initial submission

    Andy11/18/2019 at 05:35 0 comments

    Things done to date:

    1. Schematic capture and PCB layout
    2. DFM
    3. GitHub hardware repo setup
    4. Project submitted to Contest
    5. PCB's ordered

    PCB's were ordered today.  Should be around a week or so.  This is my first live experience with JLC's SMT service.  I've put together a couple test boards that I never had sent off, so I will see how this goes.  There are a couple components that JLC does not have for the board.  Most of them I have on hand, but a few I will have to order and solder on when I get the PCB's

    I need now, to switch focus and get the LoRaMac-node firmware running on these.  I've gotten it running on NucleoL073 with SX1262 MBed shield, so this shouldn't be a tough putt.  Once that is done, I'll include a link to a build-able project that should get anyone started with a LoRaWAN Feather!

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Discussions

Andy wrote 12/04/2019 at 23:15 point

Thanks!  I'm just hoping it works and isn't an undersized drink coaster like the rest of my designs!

  Are you sure? yes | no

Kirschner Christoph wrote 12/03/2019 at 07:03 point

cool project!! whats the partname of the lipo connector?

  Are you sure? yes | no

Andy wrote 12/04/2019 at 23:14 point

It's a standard JST battery connector.  https://www.digikey.com/product-detail/en/jst-sales-america-inc/S2B-PH-SM4-TB-LF-SN/455-1749-1-ND/926846

It won't be blue in final assembly, although that would be really cool, it was just the only 3d model I can find.

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davedarko wrote 12/02/2019 at 21:42 point

Nifty and way more elaborate than mine :) 

  Are you sure? yes | no

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