RAK811 based LoRa Node powered by AA batteries

End Devices (Nodes) Hardware
1

Hello everyone!
I want to share my experimental Open Source (Software and Hardware) node. I started it when RAK Wireless anounced its RUI (RakWireless Unified Inteface), which seems a great idea at that time, however at the present RUI have a lot of unfixed bugs, and their gh repo are now months with any push.

RAK811_NODE_OPEN_MEDIUM

I really think RAK811 module is a great thing, and because is based STM32L151+SX1276 (schematics are available) probably it won’t be difficult to adapt some of the software stacks floating around

The pcb design is ready to use, and the enclosure is an off the shelf “no brand”, but easy to find in your favorite online bazaar. Here is the project page:

4 Likes
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A pretty complete and nice design.
This node meets the use case i started with TTN: A good live trap monitoring for hunting purpose.

Anything on the todol list or known bugs?
What about the bugs of the RUI you mentioned?

How do you provison this device? I did not see something like a programming interface.

Most of all: Thank you for sharing!

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The serial port, boot mode, and reset signals needed to enter the STM32 factory ROM bootloader are exposed when the case is open for a battery change. So either their firmware has a command interpreter to accept a runtime change, or you compile in new details and reflash via the factory bootloader, or possibly a custom one in user flash.

For development or production, I’d prefer SWD, but a serial bootloader is potentially useful for end users since they need less equipment (the USB-UART is pretty much a requirement anyway to get status info). If I were doing a large volume, I’d personally leave off the headers so that the corresponding pads could instead be targeted by a pogo pin fixture while also eliminating a through hole soldering manufacturing step…

4

Yes, your right. It wasn’t enough clear in the project’s page how to provisioning. The device is derived from the code examples from RAK RUI, so it has a bootloader, and uses AT+ commands to provision thru UART. Here is the AT+ command manual

RAK811_AT_Command_Manual_V1.0.pdf (684.9 KB)

As @cslorabox states, all module pins are exposed, so it can be programmed also using SWD pins.

5

The “hardest” and unfixed bug in RUI api, lies in the ADC API function that assumes VCC is always 3.3v. That sort of works int RAK products powered by a 3.7 volt battery followed by a LDO 3.3v regulator.

That 3.3v assumption impacts when the module is powered by a different voltage, in this case 3V and down, so the ADC API will not work, and because the battery gauge function is based on ADC now isn’t possible to determine battery voltage.

6

Presumably you can ignore the RAK stuff for the ADC and target the hardware directly even while using RAK’s environment for the rest of the operations.

Though overall it probably makes sense to use only source-available software components…