Just trying to double-check what I read in these threads. Can RAK833 operate in USB-only mode without the need of SPI lanes. Is this correct and tested?
Thank you,
C
That depends. There are SPI only models and models with both SPI and USB. The later model works without SPI.
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Hi Everyone, i ma very new in this, can anyone help me with my problem, i got a RPi3B+ and RPi4 and i using RAK833 with PiSupply PCie board. i use the Balena Cloud and i manage to connect my 2 RPi to Balena Cloud but I CANâT connect those 2 RPi in TTN network.
I just received my RAK 833 (no USB, only SPI) and am now trying to set this up with my BananaPi R2 (it has a mPCIe Connector). Iâm pretty new to this and donât really know where to start. Any hints?
SPI on an mPCIe connector is a non-standard extension, and typically not supported on mPCIe slots in single board computers (definitely not ones on PCâs!).
However it does look like your board has an SPI bus on its GPIO connector.
Essentially, look at instructions for wiring a RAK833 to a Raspberry Pi and follow those, only using the pinout of your GPIO connector.
Youâll probably end up with a different GPIO pin name for the reset line, so youâll need to put that in the gateway reset shell script, but that shouldnât be hard.
You should be able to get this to work, itâs just going to require some care and effort.
You will need to find something to hold the mPCIe card and tap out the SPI signals though⌠often you can modify an external mPCIe to USB adapter intended for mobile data cards, by very carefully soldering fine wires to the connector base (just be careful, many of them have the voltage regulators wired to run at too high a voltage!).
Or maybe you can find a physical adapter meant for a raspberry pi and do a little hobby knife surgery to adapt the GPIO. Or maybe your GPIO pinout matches a pi⌠not saying it does but people making ARM Linux boards based on other SoCâs have copied that before.
Itâs not entirely out of the question that you could physically install the card in your SBCâs mPCIe slot but carefully use fine wires to cross-wire the USB signals to the GPIO header, itâs just that this would put your SBC board at some risk so youâd want to be good at such soldering and probably have a soldering microscope.
And no, buying the SPI model was not a mistake. The USB model uses a deprecated interface. If you really want a USB based concentrator, get the one from nFuse that uses a delegate MCU for the USB interface. But that is quirky enough that installing it in an internal slot will cause some some SBCâs not to bootâŚ
Why did you not obtain an actually mini PCIe compatible card like the n-fuse LRWCCx-MPCIE concentrator card: https://www.n-fuse.co/devices/LoRaWAN-Concentrator-Card-mini-PCIe.html
This just requires USB signals to be routed on the mini PCI slot which us conforming to the specification, though you must check that this is the case on the host that you are using.
Well, because I thought that mPCIe is a standard and the card would âjust workâ with some drivers with any mPCIe Connector, because thatâs why people would build something on top of a standard form factor⌠what does mPCIe help if its just the form factor but not using standard connections?
I also might just have bricked the RAK833 by plugging it into the mPCIe Slot of the Banana Pi R2, right?
Iâm now just going to look for a Pi Hat and stick to a well tested setup. Any hints on from where to pick one up?
Youâll be surprised what you can get away with so donât lose heart just yet.
Pi-Supply do a HAT for that board but youâll have to ask them if they do the HAT on itâs own.
RAK actually sell an adapter board for the RAK833 to USB:
which Pi Supply have in stock:
Google may well find you one closer to where ever you are.
Those only work with the USB enabled versions of the concentrator boards. Not with the SPI only versions.
If you had purchased the USB version it would work in an mPCIe slot. However, the USB version is obsolete - it uses a a deprecated design around an FT2232 USB-SPI bridge which presents a bottleneck, and as a result you have to use an old branch of the packet forwarder software (though there are 3rd party repos that mix that with other current functionality from the current Semtech branch). Fortunately in the RAK833 the USB models also support direct SPI; in the subsequent RAK2247 they do not.
SPI on an mPCIe connector is non-standard⌠but direct SPI is without a doubt the best way to interface a concentrator to an embedded system which has an SPI port - anything else is just a less efficient proxy for SPI (though the efficiency loss isnât too bad with something MCU based following from the picoGW design, as nFuse etc makes)
I also might just have bricked the RAK833 by plugging it into the mPCIe Slot of the Banana Pi R2, right?
Probably not, the SPI signals are largely on reserved pins, and to the extent that things are re-purposed they arenât used in grossly different ways. Critical damage aspects like power pins match - which is one of the reasons you can typically do surgery on an external modem holder and add wires to make it host an SPI concentrator card. You could probably even carefully solder wires to the base of the connector on your Banana Pi to bring the SPI signals over from the GPIO port, though of course you should check the board schematic first to make sure nothing else is there.
Grrrrr, this is like nailing jello to the wall. Shoot me, shoot me now.
Nah, donât bother nailing it, ship me the jello 
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Who doesnât like doing micro surgery on jello under a binocular zoom microscope?
In all seriousness, you can make a USB-mPCIe adapter work by adding wires to bring out the SPI connections, fixing the regulator voltage if it is wrong, and replacing the USB connector with a system power bus input⌠thatâs what I did before we spun custom gateway motherboards to hold an SPI-interfaced mPCIe concentrator, a USB interfaced mPCIe LTE modem, a compute platform, a few USB device ports for good measure, and assorted other goodies. Probably the most sophisticated thing actually on the board is the USB hub which is nothing more than the data sheet reference design, and the switching power supplies.
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What I really like is using a binocular zoom microscope for researcing many things. Also had some problems with an adapter but I didnât really understand much what the problem was. It just started working well one day without my interference. When trying to solve this conversation seemed to be helpful. And here is the source about microscopes and other gear that can be useful too.